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Sample records for all-pressure fluid drop

  1. Validation of an All-Pressure Fluid Drop Model: Heptane Fluid Drops in Nitrogen

    NASA Technical Reports Server (NTRS)

    Harstad, K.; Bellan, J.; Bulzan, Daniel L. (Technical Monitor)

    2000-01-01

    Despite the fact that supercritical fluids occur both in nature and in industrial situations, the fundamentals of their behavior is poorly understood because supercritical fluids combine the characteristics of both liquids and gases, and therefore their behavior is not intuitive. There are several specific reasons for the lack of understanding: First, data from (mostly optical) measurements can be very misleading because regions of high density thus observed are frequently identified with liquids. A common misconception is that if in an experiment one can optically identify "drops" and "ligaments", the observed fluid must be in a liquid state. This inference is incorrect because in fact optical measurements detect any large change (i.e. gradients) in density. Thus, the density ratio may be well below Omicron(10(exp 3)) that characterizes its liquid/gas value, but the measurement will still identify a change in the index of refraction providing that the change is sudden (steep gradients). As shown by simulations of supercritical fluids, under certain conditions the density gradients may remain large during the supercritical binary fluids mixing, thus making them optically identifiable. Therefore, there is no inconsistency between the optical observation of high density regions and the fluids being in a supercritical state. A second misconception is that because a fluid has a liquid-like density, it is appropriate to model it as a liquid. However, such fluids may have liquid-like densities while their transport properties differ from those of a liquid. Considering that the critical pressure of most fuel hydrocarbons used in Diesel and gas turbine engines is in the range of 1.5 - 3 MPa, and the fact that the maximum pressure attained in these engines is about 6 Mps, it is clear that the fuel in the combustion chamber will experience both subcritical and supercritical conditions. Studies of drop behavior over a wide range of pressures were performed in the past

  2. A Validated All-Pressure Fluid Drop Model and Lewis Number Effects for a Binary Mixture

    NASA Technical Reports Server (NTRS)

    Harstad, K.; Bellan, J.

    1999-01-01

    The differences between subcritical liquid drop and supercritical fluid drop behavior are discussed. Under subcritical, evaporative high emission rate conditions, a film layer is present in the inner part of the drop surface which contributes to the unique determination of the boundary conditions; it is this film layer which contributes to the solution's convective-diffusive character. In contrast, under supercritical condition as the boundary conditions contain a degree of arbitrariness due to the absence of a surface, and the solution has then a purely diffusive character. Results from simulations of a free fluid drop under no-gravity conditions are compared to microgravity experimental data from suspended, large drop experiments at high, low and intermediary temperatures and in a range of pressures encompassing the sub-and supercritical regime. Despite the difference between the conditions of the simulations and experiments (suspension vs. free floating), the time rate of variation of the drop diameter square is remarkably well predicted in the linear curve regime. The drop diameter is determined in the simulations from the location of the maximum density gradient, and agrees well with the data. It is also shown that the classical calculation of the Lewis number gives qualitatively erroneous results at supercritical conditions, but that an effective Lewis number previously defined gives qualitatively correct estimates of the length scales for heat and mass transfer at all pressures.

  3. Motility of active fluid drops on surfaces

    NASA Astrophysics Data System (ADS)

    Khoromskaia, Diana; Alexander, Gareth P.

    2015-12-01

    Drops of active liquid crystal have recently shown the ability to self-propel, which was associated with topological defects in the orientation of active filaments [Sanchez et al., Nature 491, 431 (2013), 10.1038/nature11591]. Here, we study the onset and different aspects of motility of a three-dimensional drop of active fluid on a planar surface. We analyze theoretically how motility is affected by orientation profiles with defects of various types and locations, by the shape of the drop, and by surface friction at the substrate. In the scope of a thin drop approximation, we derive exact expressions for the flow in the drop that is generated by a given orientation profile. The flow has a natural decomposition into terms that depend entirely on the geometrical properties of the orientation profile, i.e., its bend and splay, and a term coupling the orientation to the shape of the drop. We find that asymmetric splay or bend generates a directed bulk flow and enables the drop to move, with maximal speeds achieved when the splay or bend is induced by a topological defect in the interior of the drop. In motile drops the direction and speed of self-propulsion is controlled by friction at the substrate.

  4. Segregation in desiccated sessile drops of biological fluids.

    PubMed

    Tarasevich, Yu Yu; Pravoslavnova, D M

    2007-04-01

    It is shown here that concurrence between advection and diffusion in a drying sessile drop of a biological fluid can produce spatial redistribution of albumen and salt. The result gives an explanation for the patterns observed in the dried drops of the biological fluids.

  5. Yield-stress fluid drop impact on heated surfaces

    NASA Astrophysics Data System (ADS)

    Blackwell, Brendan; Wu, Alex; Ewoldt, Randy

    2015-11-01

    Yield-stress fluids, including gels and pastes, are effectively fluid at high stress and solid at low stress. In liquid-solid impacts, these fluids can stick and accumulate where they impact, motivating several applications of these rheologically-complex materials. Here we use high-speed imaging to experimentally study liquid-solid impact of yield-stress fluids on heated surfaces. At low temperatures yield-stress fluids tend to stick to surfaces and leave a coating layer. At sufficiently high temperatures the Leidenfrost effect can be observed, wherein a layer of vapor is created between the material and the surface due to rapid boiling, which can prevent a droplet of yield-stress fluid from sticking to the surface. In this study rheological material properties, drop size, drop velocity, and surface temperature are varied to characterize behavioral regimes. Material sticking to and releasing from the surface is observed as a function of the input parameters.

  6. Coalescence of Drops of a Power-law Fluid

    NASA Astrophysics Data System (ADS)

    Kamat, Pritish; Thete, Sumeet; Basaran, Osman

    2014-11-01

    Drop coalescence is crucial in a host of industrial, household, and natural processes that involve dispersions. Coalescence is a rate-controlling process in breaking emulsions and strongly influences drop-size-distributions in sprays. In a continuum approach, coalescence begins by the formation of a microscopic, non-slender bridge connecting the two drops. Indefinitely large axial curvature at the neck results in local lowering of pressure that drives fluid from the bulk of the drops toward the neck, thereby causing the bridge radius r (t) and height z (t) to increase in time t. The coalescence of Newtonian drops in air has heretofore been thoroughly studied. Here, we extend these earlier studies by analyzing the coalescence of drops of power-law fluids because many fluids encountered in real applications, including cosmetic creams, shampoos, grease, and paint, exhibit power-law (deformation-rate thinning) rheology. On account of the non-slender geometry of the liquid bridge connecting the two drops (z << r) , we analyze the resulting free surface flow problem by numerical simulation. Among other results, we present and discuss the nature of flows and scaling behaviors for r and z as functions of the initial viscosity and power-law index (0 < n <= 1) .

  7. Drop impact on permeable meshes with yield-stress fluids

    NASA Astrophysics Data System (ADS)

    Ewoldt, Randy; Blackwell, Brendan; Nadhan, Athrey

    2015-11-01

    Yield-stress fluids, such as pastes and gels, can stick and accumulate where they impact. To understand coating of complex topography, we experimentally study the ability of drops to accumulate on permeable solid meshes (rigid surfaces with small, evenly spaced openings). Whereas Newtonian fluids can adhere on meshes with sufficiently small lengthscales due to surface tension, yield-stress fluids can adhere due to rheological properties and accumulate much larger volumes. When inertial stresses are sufficiently high compared to the yield stress, a drop can pass through a mesh, breaking into smaller fluid particles with varying shapes, sizes, and velocities in the process. In contrast, when inertial stresses are sufficiently low compared to the yield stress, a drop can stick to the open mesh as though it were an impermeable solid surface. Drop size, impact velocity, mesh geometry, and rheological material properties are varied. Layers of spaced meshes are also examined, demonstrating a range of behaviors and the ability to coat internal aspects of complex topography. Dimensional analysis is performed to characterize material transmittance, velocity variations, and material spreading as a function of the geometric, kinematic, and rheological parameters.

  8. Measurements of fluid viscosity using a miniature ball drop device.

    PubMed

    Tang, Jay X

    2016-05-01

    This paper describes measurement of fluid viscosity using a small ball drop device. It requires as little as 100 μl of fluid. Each measurement can be performed in seconds. The experiment is designed to yield reliable viscosity values by operating at properly chosen tilt angles and with calibration using well-characterized Newtonian fluids such as mixtures of glycerol and water. It also yields dynamical viscosity of non-Newtonian fluids at moderate shear rates. The device is easy to assemble and it allows for the measurement of viscosity even when the fluid samples are too small to measure using most commercial viscometers or rheometers. Therefore, the technique is particularly useful in characterizing biological fluids such as solutions of proteins, DNA, and polymers frequently used in biomaterial applications.

  9. Measurements of fluid viscosity using a miniature ball drop device

    NASA Astrophysics Data System (ADS)

    Tang, Jay X.

    2016-05-01

    This paper describes measurement of fluid viscosity using a small ball drop device. It requires as little as 100 μl of fluid. Each measurement can be performed in seconds. The experiment is designed to yield reliable viscosity values by operating at properly chosen tilt angles and with calibration using well-characterized Newtonian fluids such as mixtures of glycerol and water. It also yields dynamical viscosity of non-Newtonian fluids at moderate shear rates. The device is easy to assemble and it allows for the measurement of viscosity even when the fluid samples are too small to measure using most commercial viscometers or rheometers. Therefore, the technique is particularly useful in characterizing biological fluids such as solutions of proteins, DNA, and polymers frequently used in biomaterial applications.

  10. Breakup modes of fluid drops in confined shear flows

    NASA Astrophysics Data System (ADS)

    Barai, Nilkamal; Mandal, Nibir

    2016-07-01

    Using a conservative level set method we investigate the deformation behavior of isolated spherical fluid drops in a fluid channel subjected to simple shear flows, accounting the following three non-dimensional parameters: (1) degree of confinement (Wc = 2a/h, where a is the drop radius and h is the channel thickness); (2) viscosity ratio between the two fluids (λ = μd/μm, where μd is the drop viscosity and μm is the matrix viscosity); and (3) capillary number (Ca). For a given Wc, a drop steadily deforms to attain a stable geometry (Taylor number and inclination of its long axis to the shear direction) when Ca < 0.3. For Ca > 0.3, the deformation behavior turns to be unsteady, leading to oscillatory variations of both its shape and orientation with progressive shear. This kind of unsteady deformation also occurs in a condition of high viscosity ratios (λ > 2). Here we present a detailed parametric analysis of the drop geometry with increasing shear as a function of Wc, Ca, and λ. Under a threshold condition, deforming drops become unstable, resulting in their breakup into smaller droplets. We recognize three principal modes of breakup: Mode I (mid-point pinching), Mode II (edge breakup), and Mode III (homogeneous breakup). Each of these modes is shown to be most effective in the specific field defined by Ca and λ. Our study also demonstrates the role of channel confinement (Wc) in controlling the transition of Mode I to III. Finally, we discuss implications of the three modes in determining characteristic drop size distributions in multiphase flows.

  11. Microseismicity Induced by Fluid Pressure Drop (Laboratory Study)

    NASA Astrophysics Data System (ADS)

    Turuntaev, Sergey; Zenchenko, Evgeny; Melchaeva, Olga

    2013-04-01

    Pore pressure change in saturated porous rocks may result in its fracturing (Maury et Fourmaintraux, 1993) and corresponding microseismic event occurrences. Microseismicity due to fluid injection is considered in numerous papers (Maxwell, 2010, Shapiro et al., 2005). Another type of the porous medium fracturing is related with rapid pore pressure drop at some boundary. The mechanism of such fracturing was considered by (Khristianovich, 1985) as a model of sudden coal blowing and by (Alidibirov, Panov, 1998) as a model of volcano eruptions. If the porous saturated medium has a boundary where it directly contacted with fluid under the high pressure (in a hydraulic fracture or in a borehole), and the pressure at that boundary is dropped, the conditions for tensile cracks can be achieved at some distance from the boundary. In the paper, the results of experimental study of saturated porous sample fracturing due to pore pressure rapid drop are discussed. The samples (82 mm high, ∅60 mm) were made of quartz sand, which was cemented by "liquid glass" glue with mass fraction 1%. The sample (porosity 35%, uniaxial unconfined compression strength 2.5 MPa) was placed in a mould and saturated by oil. The upper end of the sample contacted with the mould upper lid, the lower end contacted with fluid. The fluid pressure was increased to 10 MPa and then discharged through the bottom nipple. The pressure increases/drops were repeated 30-50 times. Pore pressure and acoustic emission (AE) were registered by transducers mounted into upper and bottom lids of the mould. It was found, that AE sources (corresponded to microfracturing) were spreading from the open end to the closed end of the sample, and that maximal number of AE events was registered at some distance from the opened end. The number of AE pulses increased with every next pressure drop, meanwhile the number of pulses with high amplitudes diminished. It was found that AE maximal rate corresponded to the fluid pressure

  12. When sticky fluids don't stick: yield-stress fluid drops on heated surfaces

    NASA Astrophysics Data System (ADS)

    Blackwell, Brendan; Wu, Alex; Ewoldt, Randy

    2016-11-01

    Yield-stress fluids, including gels and pastes, are effectively fluid at high stress and solid at low stress. In liquid-solid impacts, these fluids can stick and accumulate where they impact; this sticky behavior motivates several applications of these rheologically-complex materials. Here we describe experiments with aqueous yield stress fluids that are more 'sticky' than water at room temperature (e.g. supporting larger coating thicknesses), but are less 'sticky' at higher temperatures. Specifically, we study the conditions for aqueous yield stress fluids to bounce and slide on heated surfaces when water sticks. Here we present high-speed imaging and color interferometry to observe the thickness of the vapor layer between the drop and the surface during both stick and non-stick events. We use these data to gain insight into the physics behind the phenomenon of the yield-stress fluids bouncing and sliding, rather than sticking, on hot surfaces.

  13. Splashing, feeding, contracting: Drop impact and fluid dynamics of Vorticella

    NASA Astrophysics Data System (ADS)

    Pepper, Rachel E.

    This thesis comprises two main topics: understanding drop impact and splashing, and studying the feeding and contracting of the microorganism Vorticella. In Chapter 1, we study the effect of substrate compliance on the splash threshold of a liquid drop using an elastic membrane under variable tension. We find that splashing can be suppressed by reducing this tension. Measurements of the velocity and acceleration of the spreading drop after impact indicate that the splashing behavior is set at very early times after, or possibly just before, impact, far before the actual splash occurs. We also provide a model for the tension dependence of the splashing threshold. In Chapter 2, we study the evolution of the ejected liquid sheet, or lamella, created after impact of a liquid drop onto a solid surface using high-speed video. We find that the lamella rim thickness is always much larger than the boundary layer thickness, and that this thickness decreases with increasing impact speed. We also observe an unusual plateau behavior in thickness versus time at higher impact speeds as we approach the splash threshold. In Chapter 3, we show through calculations, simulations, and experiments that the eddies often observed near sessile filter feeders are due to the presence of nearby boundaries. We model the common filter feeder Vorticella, and also track particles around live feeding Vorticella to determine the experimental flow field. Our models are in good agreement both with each other and with the experiments. We also provide simple approximate equations to predict experimental eddy sizes due to boundaries. In Chapter 4, we show through calculations that filter feeders such as Vorticella can greatly enhance their nutrient uptake by feeding at an angle rather than perpendicular to a substrate. We also show experimental evidence that living Vorticella use this strategy. Finally, in Chapter 5, we discuss possible future directions for these projects, including potential insights

  14. Drops settling in a fluid with surface tension increasing with depth

    NASA Astrophysics Data System (ADS)

    Shapiro, Avi; Blanchette, Francois

    2011-11-01

    We investigated numerically drops settling across layers of miscible fluids, representing oil droplets settling in a fluid stratified by temperature or salinity variations. The top layer is lighter than the lower one, while the drop itself is heavier than both layers. As the drop settles into the lower, its surface tension with the ambient fluid increases, which generates significant Marangoni effects. If the surface tension difference is small, the drop is delayed as it settles into the lower layer. Above a critical surface tension difference, the drop may be altogether prevented from crossing into the lower layer. We determine the conditions under which a drop may remain suspended at the transition region, and study the mixing generated by suspended drops. We acknowledge support from NSF grant DMS 0808129.

  15. Evaporation and fluid dynamics of a sessile drop of capillary size.

    PubMed

    Barash, L Yu; Bigioni, T P; Vinokur, V M; Shchur, L N

    2009-04-01

    Theoretical description and numerical simulation of an evaporating sessile drop are developed. We jointly take into account the hydrodynamics of an evaporating sessile drop, effects of the thermal conduction in the drop, and the diffusion of vapor in air. A shape of the rotationally symmetric drop is determined within the quasistationary approximation. Nonstationary effects in the diffusion of the vapor are also taken into account. Simulation results agree well with the data of evaporation rate measurements for the toluene drop. Marangoni forces associated with the temperature dependence of the surface tension generate fluid convection in the sessile drop. Our results demonstrate several dynamical stages of the convection characterized by different number of vortices in the drop. During the early stage the array of vortices arises near a surface of the drop and induces a nonmonotonic spatial distribution of the temperature over the drop surface. The initial number of near-surface vortices in the drop is controlled by the Marangoni cell size which is similar to that given by Pearson for flat fluid layers. This number quickly decreases with time resulting in three bulk vortices in the intermediate stage. The vortices finally transform into the single convection vortex in the drop existing during about 1/2 of the evaporation time.

  16. Interferometric technique for nanoscale dynamics of fluid drops on arbitrary substrates

    NASA Astrophysics Data System (ADS)

    Verma, Gopal; Pandey, Mrityunjay; Singh, Kamal P.

    2015-07-01

    We demonstrate a simple interferometric probe to detect nanoscale dynamics of sessile fluid drops on arbitrary rough or flexible substrates. The technique relies on producing high-contrast Newton-ring like dynamical fringes by interference between a weak Fresnel reflection from the air-fluid interface of the drop and an air-glass interface of a convex lens placed above the drop in quasi-normal geometry. By analyzing the dynamical fringes, we observed 100-700 nm/s fluctuations in water drops evaporating on metal, leaves, insect wing, and sand paper due to their surface roughness. Similar fluctuations were also observed during spreading of non-volatile glycerin drops on various rough surfaces. Another application of the technique is demonstrated in precision measurement of change in evaporation rate of a water drop due to cooling of a metal substrate. This technique can be further miniaturized with a microscope objective with potential for wide applications.

  17. Osteoarthritis screening using Raman spectroscopy of dried human synovial fluid drops

    NASA Astrophysics Data System (ADS)

    Esmonde-White, Karen A.; Mandair, Gurjit S.; Esmonde-White, Francis W. L.; Raaii, Farhang; Roessler, Blake J.; Morris, Michael D.

    2009-02-01

    We describe the use of Raman spectroscopy to investigate synovial fluid drops deposited onto fused silica microscope slides. This spectral information can be used to identify chemical changes in synovial fluid associated with osteoarthritis (OA) damage to knee joints. The chemical composition of synovial fluid is predominately proteins (enzymes, cytokines, or collagen fragments), glycosaminoglycans, and a mixture of minor components such as inorganic phosphate crystals. During osteoarthritis, the chemical, viscoelastic and biological properties of synovial fluid are altered. A pilot study was conducted to determine if Raman spectra of synovial fluid correlated with radiological scoring of knee joint damage. After informed consent, synovial fluid was drawn and x-rays were collected from the knee joints of 40 patients. Raman spectra and microscope images were obtained from the dried synovial fluid drops using a Raman microprobe and indicate a coarse separation of synovial fluid components. Individual protein signatures could not be identified; Raman spectra were useful as a general marker of overall protein content and secondary structure. Band intensity ratios used to describe protein and glycosaminoglycan structure were used in synovial fluid spectra. Band intensity ratios of Raman spectra indicate that there is less ordered protein secondary structure in synovial fluid from the damage group. Combination of drop deposition with Raman spectroscopy is a powerful approach to examining synovial fluid for the purposes of assessing osteoarthritis damage.

  18. Coalescence of drops and bubbles rising through a non-Newtonian fluid in a tube.

    PubMed

    Al-Matroushi, Eisa; Borhan, Ali

    2009-04-01

    We conducted an experimental study of the interaction and coalescence of two drops (of the same fluid) or bubbles translating under the action of buoyancy in a cylindrical tube. The close approach of two Newtonian fluid particles of different size in a non-Newtonian continuous phase was examined using image analysis, and measurements of the coalescence time are reported for various particle size ratios, Bond numbers, and particle-to-suspending-fluid viscosity ratios. The flow disturbance behind the leading bubble and the viscoelastic nature of the continuous phase seemed to retard bubble coalescence. The time scale for coalescence of liquid drops in highly elastic continuous phase was influenced by the relative motion of the drops and their coalescence behavior.

  19. Determination of the shape of a free drop of magnetic fluid in a uniform magnetic field

    SciTech Connect

    Bashtovoi, V.G.; Pogirnitskaya, S.G.; Reks, A.G.

    1988-01-01

    Experimental results of previous studies were used to compare the form of a free magnetic fluid drop with an ellipsoid of revolution and to determine the range of parameters in which the experimental and theoretical data coincide. The drop has an axisymmetric shape with its symmetry axis along the field. The cross section of the drop with its plane along this axis was examined. Three parameters were selected for comparison: the area of ellipse, the sum of the focal lengths, and the radii of curvature of the various ellipses. Magnetic fluids MK-18 and MK-23 were used to study drop shape. The results of the comparison between the shape of a drop of magnetic fluid in a uniform magnetic field and an ellipsoid of revolution showed that with regard to the cross-sectional areas and the sum of the focal lengths, the forms of their surfaces nearly coincide up to sevenfold drop elongations. Dependence of the ellipsoidal shape on magnetic field strength was shown.

  20. Collision and coalescence of liquid drops in a dynamically active ambient fluid

    NASA Astrophysics Data System (ADS)

    Sambath, Krishnaraj; Subramani, Hariprasad; Basaran, Osman

    2012-11-01

    The fluid dynamics of the collision and coalescence of liquid drops has intrigued scientists and engineers for more than a century owing to its ubiquitousness in nature, e.g. raindrop coalescence, and industry, e.g. breaking of emulsions in the oil and gas industry. The complexity of the underlying dynamics, e.g. occurrence of hydrodynamic singularities, has required study of the problem at different scales - macroscopic, mesoscopic and molecular - using stochastic and deterministic methods. In this work, we adopt a multiscale, deterministic method to simulate the approach, collision, and eventual coalescence of two drops where the drops as well as the ambient fluid are incompressible, Newtonian fluids. The free boundary problem governing the dynamics consists of the Navier-Stokes system and associated initial and boundary conditions that have been augmented to account for the effects of disjoining pressure as the separation between the drops becomes of the order of a few hundred nanometers. This free boundary problem is solved by a Galerkin finite element-based algorithm. The approach and results to be reported build on earlier work by Leal and coworkers, and are used to identify conditions conducive for coalescence in terms of flow and fluid properties.

  1. Reduction, partial evaporation, and spattering - Possible chemical and physical processes in fluid drop chondrule formation

    NASA Technical Reports Server (NTRS)

    King, E. A.

    1983-01-01

    The major chemical differences between fluid drop chondrules and their probable parent materials may have resulted from the loss of volatiles such as S, H2O, Fe, and volatile siderophile elements by partial evaporation during the chondrule-forming process. Vertical access solar furnace experiments in vacuum and hydrogen have demonstrated such chemical fractionation trends using standard rock samples. The formation of immiscible iron droplets and spherules by in situ reduction of iron from silicate melt and the subsequent evaporation of the iron have been observed directly. During the time that the main sample bead is molten, many small spatter spherules are thrown off the main bead, thereby producing many additional chondrule-like melt spherules that cool rapidly and generate a population of spherules with size frequency distribution characteristics that closely approximate some populations of fluid drop chondrules in chondrites. It is possible that spatter-produced fluid drop chondrules dominate the meteoritic fluid drop chondrule populations. Such meteoritic chondrule populations should be chemically related by various relative amounts of iron and other volatile loss by vapor fractionation.

  2. Numerical vs experimental pressure drops for Boger fluids in sharp-corner contraction flow

    NASA Astrophysics Data System (ADS)

    López-Aguilar, J. E.; Tamaddon-Jahromi, H. R.; Webster, M. F.; Walters, K.

    2016-10-01

    This paper addresses the problem of matching experimental findings with numerical prediction for the extreme experimental levels of pressure-drops observed in the 4:1 sharp-corner contraction flows, as reported by Nigen and Walters ["Viscoelastic contraction flows: Comparison of axisymmetric and planar configurations," J. Non- Newtonian Fluid Mech. 102, 343-359 (2002)]. In this connection, we report on significant success in achieving quantitative agreement between predictions and experiments. This has been made possible by using a new swanINNFM model, employing an additional dissipative function. Notably, one can observe that extremely large pressure-drops may be attained with a suitable selection of the extensional viscous time scale. In addition, and on vortex structure, the early and immediate vortex enhancement for Boger fluids in axisymmetric contractions has also been reproduced, which is shown to be absent in planar counterparts.

  3. A drop in performance on a fluid intelligence test due to instructed-rule mindset.

    PubMed

    ErEl, Hadas; Meiran, Nachshon

    2016-08-17

    A 'mindset' is a configuration of processing resources that are made available for the task at hand as well as their suitable tuning for carrying it out. Of special interest, remote-relation abstract mindsets are introduced by activities sharing only general control processes with the task. To test the effect of a remote-relation mindset on performance on a Fluid Intelligence test (Raven's Advanced Progressive Matrices, RAPM), we induced a mindset associated with little usage of executive processing by requiring participants to execute a well-defined classification rule 12 times, a manipulation known from previous work to drastically impair rule-generation performance and associated cognitive processes. In Experiment 1, this manipulation led to a drop in RAPM performance equivalent to 10.1 IQ points. No drop was observed in a General Knowledge task. In Experiment 2, a similar drop in RAPM performance was observed (equivalent to 7.9 and 9.2 IQ points) regardless if participants were pre-informed about the upcoming RAPM test. These results indicate strong (most likely, transient) adverse effects of a remote-relation mindset on test performance. They imply that although the trait of Fluid Intelligence has probably not changed, mindsets can severely distort estimates of this trait.

  4. An undergraduate lab on measuring fluid viscosity using a miniature ball drop device

    NASA Astrophysics Data System (ADS)

    Tang, Jay

    2015-11-01

    I would like to describe measurement of fluid viscosity using a small ball drop device. It requires as little as 100 microliters of fluid. Each measurement can be performed in seconds. Through simple experimentation, students observe fluid flow confined in a thin cylindrical tube. They analyze forces and torques on a tiny ball falling and rolling down in an inclined tube. They gain practice in observing and identifying sources of errors and variability in their measurements beyond those indicated by standard error bars. The experiment is designed to yield reliable viscosity values by operating at properly chosen tilt angles and with calibration using well-characterized fluids such as mixtures of glycerol and water. The technique is also useful in research and technological applications as the device is easy to assemble and it allows the measurement of viscosity even when the fluid samples are too small to measure using most commercial viscometers or rheometers. Work Partially Supported by the NSF Fluid Physics Program (Award number CBET 1438033).

  5. Fluid dynamics and deposit patterns in evaporating sessile drop containing microparticles: substrate heating and wettability effects

    NASA Astrophysics Data System (ADS)

    Patil, Nagesh D.; Bhardwaj, Rajneesh; Sharma, Atul

    2016-11-01

    The evaporation of sessile water drops containing colloidal microparticles is investigated on non-heated and heated hydrophilic and hydrophobic substrates. Time-varying drop shapes and temperatures of liquid-gas interface are recorded using high-speed and infrared camera, respectively. In heated case, infrared-thermography shows larger temperature gradient across the liquid-gas interface and recorded motion of the particles confirm Marangoni flow from the contact line to apex inside the drop. On non-heated hydrophilic substrates, a ring-like pattern forms, as reported extensively in the literature; while on heated hydrophilic substrates, a thin ring with an inner-deposit forms. On non-heated hydrophobic substrates, the contact line depins to form inner-deposit without ring; while on heated hydrophobic substrates, the contact line pins to form inner-deposit with thin ring. This pinning transition occurs due to the particles self-pinning in a stagnation region developed by the Marangoni flow near the contact line. This work gives fundamental insights on the thermal and wettability effects on internal fluid dynamics of the evaporating sessile drop and associated deposit shape, with applications in ink-jet printing and biosensors. PhD Scholar.

  6. Electric driven instability in a charged drop immersed in a viscous dielectric fluid

    NASA Astrophysics Data System (ADS)

    Miloh, Touvia

    2014-07-01

    Linear stability analysis is performed on an electrically charged spherical viscous liquid drop with a spherical rigid core surrounded by a second Newtonian uncharged fluid of different dielectric properties. Dispersion relation and growth rate of the most unstable interfacial mode is found by taking into account, viscous, electrostatic, gravity, and surface tension effects. Several physical interesting cases, such as drop oscillations in vacuum or those involving planar 2D interfaces, are obtained as limiting cases. Numerical simulations are performed for various geometrics, flow, and electric parameters in order to determine the threshold value of the applied voltage or electric charge which lead to multi-jetting phenomena on the interface. The characteristic wave-length (spacing) and size of these radial protrusions is determined in terms of the electric forcing which is an important design parameter for the controlled needleless electrospinning phenomena.

  7. Investigation of the different base fluid effects on the nanofluids heat transfer and pressure drop

    NASA Astrophysics Data System (ADS)

    Bayat, Javad; Nikseresht, Amir Hossein

    2011-09-01

    A numerical study of laminar forced convective flows of three different nanofluids through a horizontal circular tube with a constant heat flux condition has been performed. The effect of Al2O3 volume concentration 0 ≤ φ ≤ 0.09 in the pure water, water-ethylene glycol mixture and pure ethylene glycol as base fluids, and Reynolds number of 100 ≤ Re ≤ 2,000 for different power inputs in the range of 10 ≤ Q( W) ≤ 400 have been investigated. In this study, all of the nanofluid properties are temperature and nanoparticle volume concentration dependent. The governing equations have been solved using finite volume approach with the SIMPLER algorithm. The results indicate an increase in the averaged heat transfer coefficient with increasing the mass of ethylene glycol in the water base fluid, solid concentration and Reynolds number. From the investigations it can be inferred that, the pressure drop and pumping power in the nanofluids at low solid volumetric concentration (φ < 3%) is approximately the same as in the pure base fluid in the various Reynolds numbers, but the higher solid nanoparticle volume concentration causes a penalty drop in the pressure. Moreover, this study shows it is possible to achieve a higher heat transfer rate with lower wall shear stress with the use of proper nanofluids.

  8. Gravity-Dependent Combustion and Fluids Research - From Drop Towers to Aircraft to the ISS

    NASA Technical Reports Server (NTRS)

    Urban, David L.; Singh, Bhim S.; Kohl, Fred J.

    2007-01-01

    Driven by the need for knowledge related to the low-gravity environment behavior of fluids in liquid fuels management, thermal control systems and fire safety for spacecraft, NASA embarked on a decades long research program to understand, accommodate and utilize the relevant phenomena. Beginning in the 1950s, and continuing through to today, drop towers and aircraft were used to conduct an ever broadening and increasingly sophisticated suite of experiments designed to elucidate the underlying gravity-dependent physics that drive these processes. But the drop towers and aircraft afford only short time periods of continuous low gravity. Some of the earliest rocket test flights and manned space missions hosted longer duration experiments. The relatively longer duration low-g times available on the space shuttle during the 1980s and 1990s enabled many specialized experiments that provided unique data for a wide range of science and engineering disciplines. Indeed, a number of STS-based Spacelab missions were dedicated solely to basic and applied microgravity research in the biological, life and physical sciences. Between 1980 and 2000, NASA implemented a vigorous Microgravity Science Program wherein combustion science and fluid physics were major components. The current era of space stations from the MIR to the International Space Station have opened up a broad range of opportunities and facilities that are now available to support both applied research for technologies that will help to enable the future exploration missions and for a continuation of the non-exploration basic research that began over fifty years ago. The ISS-based facilities of particular value to the fluid physics and combustion/fire safety communities are the Fluids and Combustion Facility Combustion Integrated Rack and the Fluids Integrated Rack.

  9. Effect of capillary forces on the nonstationary fall of a drop in an infinite fluid

    NASA Astrophysics Data System (ADS)

    Antanovskii, L. K.

    1991-12-01

    An explicit solution is presented for the linear problem concerning the motion of a drop in an infinite fluid in the presence of any number of surfactants (chemical reactions are not considered in the first approximation). It is shown that the behavior of the system considered is consistent with the Le Chatelier principle. The reactivity of the capillary forces is directly related to the fundamental principles of thermodynamics, which makes it possible to write equations of surfactant thermodiffusion in symmetric form and obtain a relatively simple solution to the linearized problem.

  10. Using the sessile drop geometry to measure fluid and elastic block copolymer interfaces.

    PubMed

    Rozairo, Damith P; Croll, Andrew B

    2015-02-03

    There is considerable interest in the fabrication and mechanics of soft spheres and capsules because of their use in a large number of applications ranging from targeted drug delivery to cosmetically active agents. Many systems, such as lipid and block copolymer vesicles, are already finding considerable industrial use where the performance of soft spheres depends intimately on their mechanics. New advanced features such as fast cargo delivery can be realized only if they fit into the existing mechanical niche of the system in question. Here we present a model system to demonstrate how a capsule structure can be fundamentally changed while maintaining its overall mechanical response as well as a simple, universal method to measure the resulting capsule material properties. Specifically, we use confocal microscopy to adapt the sessile drop geometry to a measurement of the static properties of an ensemble of polystyrene-b-poly(ethylene oxide) (PS-PEO)-stabilized oil droplets. We then synthesize a polystyrene-b-poly(acrylic acid)-b-polystyrene (PS-PAA-PS) elastic-shell-coated emulsion drop that shows an identical deformation to the fluidlike PS-PEO droplets. Both systems, in sessile geometry, can be related to their basic material properties through appropriate modeling. We find that the elastic shell is dominated by its surface tension, easily enabling it to match the static response of a purely fluid drop.

  11. Non-Toxic, Low-Freezing, Drop-In Replacement Heat Transfer Fluids

    NASA Technical Reports Server (NTRS)

    Cutbirth, J. Michael

    2012-01-01

    A non-toxic, non-flammable, low-freezing heat transfer fluid is being developed for drop-in replacement within current and future heat transfer loops currently using water or alcohol-based coolants. Numerous water-soluble compounds were down-selected and screened for toxicological, physical, chemical, compatibility, thermodynamic, and heat transfer properties. Two fluids were developed, one with a freezing point near 0 C, and one with a suppressed freezing point. Both fluids contain an additive package to improve material compatibility and microbial resistance. The optimized sub-zero solution had a freezing point of 30 C, and a freezing volume expansion of 10-percent of water. The toxicity of the solutions was experimentally determined as LD(50) greater than 5g/kg. The solutions were found to produce minimal corrosion with materials identified by NASA as potentially existing in secondary cooling loops. Thermal/hydrodynamic performance exceeded that of glycol-based fluids with comparable freezing points for temperatures Tf greater than 20 C. The additive package was demonstrated as a buffering agent to compensate for CO2 absorption, and to prevent microbial growth. The optimized solutions were determined to have physically/chemically stable shelf lives for freeze/thaw cycles and longterm test loop tests.

  12. Surface Forces and Interaction Mechanisms of Emulsion Drops and Gas Bubbles in Complex Fluids.

    PubMed

    Xie, Lei; Shi, Chen; Cui, Xin; Zeng, Hongbo

    2017-02-22

    The interactions of emulsion drops and gas bubbles in complex fluids play important roles in a wide range of biological and technological applications, such as programmable drug and gene delivery, emulsion and foam formation, and froth flotation of mineral particles. In this feature article, we have reviewed our recent progress on the quantification of surface forces and interaction mechanisms of gas bubbles and emulsion drops in different material systems by using several complementary techniques, including the drop/bubble probe atomic force microscope (AFM), surface forces apparatus (SFA), and four-roll mill fluidic device. These material systems include the bubble-self-assembled monolayer (SAM), bubble-polymer, bubble-superhydrophobic surface, bubble-mineral, water-in-oil and oil-in-water emulsions with interface-active components in oil production, and oil/water wetting on polyelectrolyte surfaces. The bubble probe AFM combined with reflection interference contrast microscopy (RICM) was applied for the first time to simultaneously quantify the interaction forces and spatiotemporal evolution of a confined thin liquid film between gas bubbles and solid surfaces with varying hydrophobicity. The nanomechanical results have provided useful insights into the fundamental interaction mechanisms (e.g., hydrophobic interaction in aqueous media) at gas/water/solid interfaces, the stabilization/destabilization mechanisms of emulsion drops, and oil/water wetting mechanisms on solid surfaces. A long-range hydrophilic attraction was found between water and polyelectrolyte surfaces in oil, with the strongest attraction for polyzwitterions, contributing to their superior water wettability in oil and self-cleaning capability of oil contamination. Some remaining challenges and future research directions are discussed and provided.

  13. Fast imaging technique to study drop impact dynamics of non-Newtonian fluids.

    PubMed

    Xu, Qin; Peters, Ivo; Wilken, Sam; Brown, Eric; Jaeger, Heinrich

    2014-03-05

    In the field of fluid mechanics, many dynamical processes not only occur over a very short time interval but also require high spatial resolution for detailed observation, scenarios that make it challenging to observe with conventional imaging systems. One of these is the drop impact of liquids, which usually happens within one tenth of millisecond. To tackle this challenge, a fast imaging technique is introduced that combines a high-speed camera (capable of up to one million frames per second) with a macro lens with long working distance to bring the spatial resolution of the image down to 10 µm/pixel. The imaging technique enables precise measurement of relevant fluid dynamic quantities, such as the flow field, the spreading distance and the splashing speed, from analysis of the recorded video. To demonstrate the capabilities of this visualization system, the impact dynamics when droplets of non-Newtonian fluids impinge on a flat hard surface are characterized. Two situations are considered: for oxidized liquid metal droplets we focus on the spreading behavior, and for densely packed suspensions we determine the onset of splashing. More generally, the combination of high temporal and spatial imaging resolution introduced here offers advantages for studying fast dynamics across a wide range of microscale phenomena.

  14. Equilibrium shapes and stability of nonconducting pendant drops surrounded by a conducting fluid in an electric field

    SciTech Connect

    Harris, M.T.; Basaran, O.A.

    1995-03-15

    The shapes and stability of pendant drops in the presence of an electric field is a classical problem in capillarity. This problem has been studied in great detail by numerous investigators when the drops are either perfect conductors or nonconductors and the surrounding fluid is a nonconductor. In this paper, the axisymmetric equilibrium shapes and stability of a nonconducting drop hanging from a nonconducting nozzle that is immersed in a perfectly conducting ambient fluid, a problem that has heretofore not been considered in the literature, are determined by solving the free boundary problem comprised of the Young-Laplace equation for drop shape and an integral equation for the electric field distribution. Here the free boundary problem is discretized by a hybrid technique in which the Young-Laplace equation is solved by the finite element method and the electrostatic problem solved by the boundary element method.

  15. Fluid-structure interaction analysis of the drop impact test for helicopter fuel tank.

    PubMed

    Yang, Xianfeng; Zhang, Zhiqiang; Yang, Jialing; Sun, Yuxin

    2016-01-01

    The crashworthiness of helicopter fuel tank is vital to the survivability of the passengers and structures. In order to understand and improve the crashworthiness of the soft fuel tank of helicopter during the crash, this paper investigated the dynamic behavior of the nylon woven fabric composite fuel tank striking on the ground. A fluid-structure interaction finite element model of the fuel tank based on the arbitrary Lagrangian-Eulerian method was constructed to elucidate the dynamic failure behavior. The drop impact tests were conducted to validate the accuracy of the numerical simulation. Good agreement was achieved between the experimental and numerical results of the impact force with the ground. The influences of the impact velocity, the impact angle, the thickness of the fuel tank wall and the volume fraction of water on the dynamic responses of the dropped fuel tank were studied. The results indicated that the corner of the fuel tank is the most vulnerable location during the impact with ground.

  16. Sizing of colloidal particle and protein molecules in a hanging fluid drop

    NASA Technical Reports Server (NTRS)

    Ansari, Rafat R.; Suh, Kwang I.

    1995-01-01

    We report non-invasive particle size measurements of polystyrene latex colloidal particles and bovine serum albumin (BSA) protein molecules suspended in tiny hanging fluid drops of 30 micro-Liter volume using a newly designed fiber optic probe. The probe is based upon the principles of the technique of dynamic light scattering (DLS). The motivation for this work comes from growing protein crystals in outer space. Protein crystals have been grown previously in hanging drops in microgravity experiments on-board the space shuttle orbiter. However, obtaining quantitative information on nucleation and growth of the protein crystals in real time has always been a desired goal, but hitherto not achieved. Several protein researchers have shown interest in using DLS to monitor crystal growth process in a droplet, but elaborate instrumentation and optical alignment problems have made in-situ applications difficult. We demonstrate that such an experiment is now possible. Our system offers fast (5 seconds) determination of particle size, utilize safe levels of very low laser power (less than or equal to 0.2 mW), a small scattering volume (approximately 2 x 10(exp -5) cu mm) and high spatial coherence (Beta) values. This is a major step forward when compared to currently available DLS systems.

  17. Lateral migration of a viscoelastic drop in a Newtonian fluid in a shear flow near a wall.

    PubMed

    Mukherjee, Swarnajay; Sarkar, Kausik

    2014-10-01

    Wall induced lateral migration of a viscoelastic (FENE-MCR) drop in a Newtonian fluid is investigated. Just like a Newtonian drop, a viscoelastic drop reaches a quasi-steady state where the lateral velocity only depends on the instantaneous distance from the wall. The drop migration velocity and the deformation scale inversely with the square and the cube of the distance from the wall, respectively. The migration velocity varies non-monotonically with increasing viscoelasticity (increasing Deborah number); initially increasing and then decreasing. An analytical explanation has been given of the effects by computing the migration velocity as arising from an image stresslet field due to the drop. The semi-analytical expression matches well with the simulated migration velocity away from the wall. It contains a viscoelastic stresslet component apart from those arising from interfacial tension and viscosity ratio. The migration dynamics is a result of the competition between the viscous (interfacial tension and viscosity ratio) and the viscoelastic effects. The viscoelastic stresslet contribution towards the migration velocity steadily increases. But the interfacial stresslet-arising purely from the drop shape-first increases and then decreases with rising Deborah number causing the migration velocity to be non-monotonic. The geometric effect of the interfacial stresslet is caused by a corresponding nonmonotonic variation of the drop inclination. High viscosity ratio is briefly considered to show that the drop viscoelasticity could stabilize a drop against breakup, and the increase in migration velocity due to viscoelasticity is larger compared to the viscosity-matched case.

  18. Merging drops in a Teflon tube, and transferring fluid between them, illustrated by protein crystallization and drug screening.

    PubMed

    Feuerborn, A; Prastowo, A; Cook, P R; Walsh, E

    2015-01-01

    The ability to manipulate drops with small volumes has many practical applications. Current microfluidic devices generally exploit channel geometry and/or active external equipment to control drops. Here we use a Teflon tube attached to a syringe pump and exploit the properties of interfaces between three immiscible liquids to create particular fluidic architectures. We then go on to merge any number of drops (with volumes of micro- to nano-liters) at predefined points in time and space in the tube; for example, 51 drops were merged in a defined order to yield one large drop. Using a different architecture, specified amounts of fluid were transferred between 2 nl drops at specified rates; for example, 2.5 pl aliquots were transferred (at rates of ~500 fl s(-1)) between two drops through inter-connecting nano-channels (width ~40 nm). One proof-of-principle experiment involved screening conditions required to crystallize a protein (using a concentration gradient created using such nano-channels). Another demonstrated biocompatibility; drugs were mixed with human cells grown in suspension or on surfaces, and the treated cells responded like those grown conventionally. Although most experiments were performed manually, moderate high-throughput potential was demonstrated by mixing ~1000 different pairs of 50 nl drops in ~15 min using a robot. We suggest this reusable, low-cost, and versatile methodology could facilitate the introduction of microfluidics into workflows of many experimental laboratories.

  19. On axial temperature gradients due to large pressure drops in dense fluid chromatography.

    PubMed

    Colgate, Sam O; Berger, Terry A

    2015-03-13

    The effect of energy degradation (Degradation is the creation of net entropy resulting from irreversibility.) accompanying pressure drops across chromatographic columns is examined with regard to explaining axial temperature gradients in both high performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC). The observed effects of warming and cooling can be explained equally well in the language of thermodynamics or fluid dynamics. The necessary equivalence of these treatments is reviewed here to show the legitimacy of using whichever one supports the simpler determination of features of interest. The determination of temperature profiles in columns by direct application of the laws of thermodynamics is somewhat simpler than applying them indirectly by solving the Navier-Stokes (NS) equations. Both disciplines show that the preferred strategy for minimizing the reduction in peak quality caused by temperature gradients is to operate columns as nearly adiabatically as possible (i.e. as Joule-Thomson expansions). This useful fact, however, is not widely familiar or appreciated in the chromatography community due to some misunderstanding of the meaning of certain terms and expressions used in these disciplines. In fluid dynamics, the terms "resistive heating" or "frictional heating" have been widely used as synonyms for the dissipation function, Φ, in the NS energy equation. These terms have been widely used by chromatographers as well, but often misinterpreted as due to friction between the mobile phase and the column packing, when in fact Φ describes the increase in entropy of the system (dissipation, ∫TdSuniv>0) due to the irreversible decompression of the mobile phase. Two distinctly different contributions to the irreversibility are identified; (1) ΔSext, viscous dissipation of work done by the external surroundings driving the flow (the pump) contributing to its warming, and (2) ΔSint, entropy change accompanying decompression of

  20. Harnessing fluid-driven vesicles to pick up and drop off Janus particles.

    PubMed

    Salib, Isaac; Yong, Xin; Crabb, Emily J; Moellers, Nicholas M; McFarlin, Gerald T; Kuksenok, Olga; Balazs, Anna C

    2013-02-26

    Using dissipative particle dynamics (DPD) simulations, we model the interaction between nanoscopic lipid vesicles and Janus nanoparticles in the presence of an imposed flow. Both the vesicle and Janus nanoparticles are localized on a hydrophilic substrate and immersed in a hydrophilic solution. The fluid-driven vesicle successfully picks up Janus particles on the substrate and transports these particles as cargo along the surface. The vesicle can carry up to four particles as its payload. Hence, the vesicles can act as nanoscopic "vacuum cleaners", collecting nanoscopic debris localized on the floors of the fluidic devices. Importantly, these studies reveal how an imposed flow can facilitate the incorporation of nanoparticles into nanoscale vesicles. With the introduction of a "sticky" domain on the substrate, the vesicles can also robustly drop off and deposit the particles on the surface. The controlled pickup and delivery of nanoparticles via lipid vesicles can play an important step in the bottom-up assembly of these nanoparticles within small-scale fluidic devices.

  1. Harnessing Fluid-Driven Vesicles to Pick Up and Drop Off Janus Particles

    NASA Astrophysics Data System (ADS)

    Yong, Xin; Salib, Isaac; Crabb, Emily; Moellers, Nicholas; McFarlin, Gerald; Kuksenok, Olga; Balazs, Anna

    2013-03-01

    Using dissipative particle dynamics (DPD) simulations, we model the interaction between nanoscopic lipid vesicles and Janus nanoparticles in the presence of an imposed flow. Both the vesicle and Janus nanoparticles are localized on a hydrophilic substrate and immersed in a hydrophilic solution. The fluid-driven vesicle successfully picks up Janus particles on the substrate and transports these particles as cargo along the surface. The vesicle can carry up to four particles as its payload. Hence, the vesicles can acts as nanoscopic ``vacuum cleaners'', collecting nanoscopic debris localized on the floors of the fluidic devices. Importantly, these studies reveal how an imposed flow can facilitate the incorporation of nanoparticles into nanoscale vesicles. With the introduction of a hydrophobic domain on the substrate, the vesicles can also robustly drop off and deposit the particles on the surface. The controlled pickup and delivery of nanoparticles via lipid vesicles can play an important step in the bottom-up assembly of these nanoparticles within small-scale fluidic devices.

  2. Lateral migration of a viscoelastic drop in a Newtonian fluid in a shear flow near a wall

    PubMed Central

    Mukherjee, Swarnajay; Sarkar, Kausik

    2014-01-01

    Wall induced lateral migration of a viscoelastic (FENE-MCR) drop in a Newtonian fluid is investigated. Just like a Newtonian drop, a viscoelastic drop reaches a quasi-steady state where the lateral velocity only depends on the instantaneous distance from the wall. The drop migration velocity and the deformation scale inversely with the square and the cube of the distance from the wall, respectively. The migration velocity varies non-monotonically with increasing viscoelasticity (increasing Deborah number); initially increasing and then decreasing. An analytical explanation has been given of the effects by computing the migration velocity as arising from an image stresslet field due to the drop. The semi-analytical expression matches well with the simulated migration velocity away from the wall. It contains a viscoelastic stresslet component apart from those arising from interfacial tension and viscosity ratio. The migration dynamics is a result of the competition between the viscous (interfacial tension and viscosity ratio) and the viscoelastic effects. The viscoelastic stresslet contribution towards the migration velocity steadily increases. But the interfacial stresslet—arising purely from the drop shape—first increases and then decreases with rising Deborah number causing the migration velocity to be non-monotonic. The geometric effect of the interfacial stresslet is caused by a corresponding nonmonotonic variation of the drop inclination. High viscosity ratio is briefly considered to show that the drop viscoelasticity could stabilize a drop against breakup, and the increase in migration velocity due to viscoelasticity is larger compared to the viscosity-matched case. PMID:25378894

  3. A New Formulation for Volume-of-Fluid Simulations of Drops on Solid Surfaces: Inclusion of Adhesion Force

    NASA Astrophysics Data System (ADS)

    Chang, C.; Criscione, A.; Jakirlic, S.; Tropea, C.; Amirfazli, Alidad

    2012-11-01

    The capillary forces acting on a sessile drop placed on a solid surface has two basic components: (1) the Laplace pressure (LP) due to the curvature of the liquid-gas interface, and (2) the Surface Tension Force (STF) as a concentrated force acting at the three-phase contact line. STF can be thought of adhesion force for a drop placed on a solid surface. To date, Volume-of-Fluid (VoF) simulations of drops on solid surfaces have only considered LP, and ignored the STF. Ignoring the STF can lead to incorrect description of the physics for systems involving sessile drops (e.g. shedding of a drop from a surface) especially when capillary and external (e.g. inertial) forces are of the same order of magnitude. Continuum Surface Force (CSF) method is widely used in VoF to model the LP. By modifying the CSF implementation at the contact line, we have added the STF to the VoF formulation. Two case studies, i.e. water drops on an inclined surface and a sessile drop exposed to a shearing airflow are considered. When the STF was ignored, a drop placed on an inclined surface moved at an unrealistically low inclination (e.g. 1 degree for a system with considerable contact angle hysteresis of 10-30 deg.). Same unrealistic motion for the drop was observed when exposed to very low air velocities. Inclusion of the STF corrected both of these unphysical outcomes. A discussion of various systems with different wettabilities (adhesion force values) for each of the two case studies will be provided and comparisons with experiments will be presented.

  4. Modeling the vertical motion of drops bouncing on a bounded fluid reservoir

    NASA Astrophysics Data System (ADS)

    Blanchette, François

    2016-03-01

    We present a first-principles model of drops bouncing on a liquid reservoir. We consider a nearly inviscid liquid reservoir and track the waves that develop in a bounded domain. Bouncing drops are modeled as vertical linear springs. We obtain an expression for the contact force between drop and liquid surface and a model where the only adjustable parameter is an effective viscosity used to describe the waves on the reservoir's surface. With no adjustable parameters associated to the drop, we recover experimental bouncing times and restitution coefficients. We use our model to describe the effect of the Bond, Ohnesorge, and Weber numbers on drops bouncing on a stationary reservoir. We also use our model to describe drops bouncing on an oscillated reservoir, describing various bouncing modes and a walking threshold.

  5. Scaling crossover in thin-film drag dynamics of fluid drops in the Hele-Shaw cell.

    PubMed

    Yahashi, Misato; Kimoto, Natsuki; Okumura, Ko

    2016-08-26

    We study both experimentally and theoretically the descending motion due to gravity of a fluid drop surrounded by another immiscible fluid in a confined space between two parallel plates, i.e., in the Hele-Shaw cell. As a result, we show a new scaling regime of a nonlinear drag friction in viscous liquid that replaces the well-known Stokes' drag friction through a clear collapse of experimental data thanks to the scaling law. In the novel regime, the dissipation in the liquid thin film formed between the drop and cell walls governs the dynamics. The crossover of this scaling regime to another scaling regime in which the dissipation inside the droplet is dominant is clearly demonstrated and a phase diagram separating these scaling regimes is presented.

  6. Scaling crossover in thin-film drag dynamics of fluid drops in the Hele-Shaw cell

    NASA Astrophysics Data System (ADS)

    Yahashi, Misato; Kimoto, Natsuki; Okumura, Ko

    2016-08-01

    We study both experimentally and theoretically the descending motion due to gravity of a fluid drop surrounded by another immiscible fluid in a confined space between two parallel plates, i.e., in the Hele-Shaw cell. As a result, we show a new scaling regime of a nonlinear drag friction in viscous liquid that replaces the well-known Stokes’ drag friction through a clear collapse of experimental data thanks to the scaling law. In the novel regime, the dissipation in the liquid thin film formed between the drop and cell walls governs the dynamics. The crossover of this scaling regime to another scaling regime in which the dissipation inside the droplet is dominant is clearly demonstrated and a phase diagram separating these scaling regimes is presented.

  7. Scaling crossover in thin-film drag dynamics of fluid drops in the Hele-Shaw cell

    PubMed Central

    Yahashi, Misato; Kimoto, Natsuki; Okumura, Ko

    2016-01-01

    We study both experimentally and theoretically the descending motion due to gravity of a fluid drop surrounded by another immiscible fluid in a confined space between two parallel plates, i.e., in the Hele-Shaw cell. As a result, we show a new scaling regime of a nonlinear drag friction in viscous liquid that replaces the well-known Stokes’ drag friction through a clear collapse of experimental data thanks to the scaling law. In the novel regime, the dissipation in the liquid thin film formed between the drop and cell walls governs the dynamics. The crossover of this scaling regime to another scaling regime in which the dissipation inside the droplet is dominant is clearly demonstrated and a phase diagram separating these scaling regimes is presented. PMID:27562151

  8. Scaling crossover in thin-film drag dynamics of fluid drops in the Hele-Shaw cell

    NASA Astrophysics Data System (ADS)

    Okumura, Ko; Yahashi, Misato; Kimoto, Natsuki

    2016-11-01

    We study both experimentally and theoretically the descending motion due to gravity of a fluid drop surrounded by another immiscible fluid in a confined space between two parallel plates, i.e., in the Hele-Shaw cell. As a result, we show a new scaling regime of a nonlinear drag friction in viscous liquid that replaces the well-known Stokes' drag friction through a clear collapse of experimental data thanks to the scaling law. In the novel regime, the dissipation in the liquid thin film formed between the drop and cell walls governs the dynamics. The crossover of this scaling regime to another scaling regime in which the dissipation inside the droplet is dominant is clearly demonstrated and a phase diagram separating these scaling regimes is presented. To be published as, Y. Yahashi, N. Kimoto and K. Okumura, Scaling crossover in thin-film drag dynamics of fluid drops in the Hele-Shaw cell, Sci. Rep.(CC BY 4.0). This research was partly supported by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).

  9. Near-field acousto monitoring shear interactions inside a drop of fluid: The role of the zero-slip condition

    NASA Astrophysics Data System (ADS)

    Wang, Xiaohua; Fernandez, Rodolfo; Li, Nan; Hung, Hsien-Chih; Venkataraman, Anuradha; Nordstrom, Richard; La Rosa, Andres H.

    2016-05-01

    A full understanding of nanometer-range (near-field) interactions between two sliding solid boundaries, with a mesoscopic fluid layer sandwiched in between, remains challenging. In particular, the origin of the blue-shift resonance frequency experienced by a laterally oscillating probe when approaching a substrate is still a matter of controversy. A simpler problem is addressed here, where a laterally oscillating solid probe interacts with a more sizable drop of fluid that rests on a substrate, aiming at identifying interaction mechanisms that could also be present in the near-field interaction case. It is found that the inelastic component of the probe-fluid interaction does not constitute the main energy-dissipation channel and has a weak dependence on fluid's viscosity, which is attributed to the zero-slip hydrodynamic condition. In contrast, the acoustic signal engendered by the fluid has a stronger dependence on the fluid's viscosity (attributed also to the zero-slip hydrodynamic condition) and correlates well with the probe's resonance frequency red-shift. We propose a similar mechanism happens in near field experiments, but a blue-shift in the probe's resonance results as a consequence of the fluid molecules (subjected to the zero-slip condition at both the probe and substrate boundaries) exerting instead a spring type restoring force on the probe.

  10. Overall heat transfer coefficient and pressure drop in a typical tubular exchanger employing alumina nano-fluid as the tube side hot fluid

    NASA Astrophysics Data System (ADS)

    Kabeel, A. E.; Abdelgaied, Mohamed

    2016-08-01

    Nano-fluids are used to improve the heat transfer rates in heat exchangers, especially; the shell-and-tube heat exchanger that is considered one of the most important types of heat exchangers. In the present study, an experimental loop is constructed to study the thermal characteristics of the shell-and-tube heat exchanger; at different concentrations of Al2O3 nonmetallic particles (0.0, 2, 4, and 6 %). This material concentrations is by volume concentrations in pure water as a base fluid. The effects of nano-fluid concentrations on the performance of shell and tube heat exchanger have been conducted based on the overall heat transfer coefficient, the friction factor, the pressure drop in tube side, and the entropy generation rate. The experimental results show that; the highest heat transfer coefficient is obtained at a nano-fluid concentration of 4 % of the shell side. In shell side the maximum percentage increase in the overall heat transfer coefficient has reached 29.8 % for a nano-fluid concentration of 4 %, relative to the case of the base fluid (water) at the same tube side Reynolds number. However; in the tube side the maximum relative increase in pressure drop has recorded the values of 12, 28 and 48 % for a nano-material concentration of 2, 4 and 6 %, respectively, relative to the case without nano-fluid, at an approximate value of 56,000 for Reynolds number. The entropy generation reduces with increasing the nonmetallic particle volume fraction of the same flow rates. For increase the nonmetallic particle volume fraction from 0.0 to 6 % the rate of entropy generation decrease by 10 %.

  11. High-Pressure Transport Properties Of Fluids: Theory And Data From Levitated Drops At Combustion-Relevant Temperatures

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Harstad, Kenneth; Ohsaka, Kenichi

    2003-01-01

    Although the high pressure multicomponent fluid conservation equations have already been derived and approximately validated for binary mixtures by this PI, the validation of the multicomponent theory is hampered by the lack of existing mixing rules for property calculations. Classical gas dynamics theory can provide property mixing-rules at low pressures exclusively. While thermal conductivity and viscosity high-pressure mixing rules have been documented in the literature, there is no such equivalent for the diffusion coefficients and the thermal diffusion factors. The primary goal of this investigation is to extend the low pressure mixing rule theory to high pressures and validate the new theory with experimental data from levitated single drops. The two properties that will be addressed are the diffusion coefficients and the thermal diffusion factors. To validate/determine the property calculations, ground-based experiments from levitated drops are being conducted.

  12. Pressure, temperature and density drops along supercritical fluid chromatography columns. I. Experimental results for neat carbon dioxide and columns packed with 3- and 5-micron particles.

    PubMed

    Poe, Donald P; Veit, Devon; Ranger, Megan; Kaczmarski, Krzysztof; Tarafder, Abhijit; Guiochon, Georges

    2012-08-10

    The pressure drop and temperature drop on columns packed with 3- and 5-micron particles were measured using neat CO(2) at a flow rate of 5 mL/min, at temperatures from 20°C to 100°C, and outlet pressures from 80 to 300 bar. The density drop was calculated based on the temperature and pressure at the column inlet and outlet. The columns were suspended in a circulating air bath either bare or covered with foam insulation. The results show that the pressure drop depends on the outlet pressure, the operating temperature, and the thermal environment. A temperature drop was observed for all conditions studied. The temperature drop was relatively small (less than 3°C) for combinations of low temperature and high pressure. Larger temperature drops and density drops occurred at higher temperatures and low to moderate pressures. Covering the column with thermal insulation resulted in larger temperature drops and corresponding smaller density drops. At 20°C the temperature drop was never more than a few degrees. The largest temperature drops occurred for both columns when insulated at 80°C and 80 bar, reaching a maximum value of 21°C for the 5-micron column, and 26°C for the 3-micron column. For an adiabatic column, the temperature drop depends on the pressure drop, the thermal expansion coefficient, and the density and the heat capacity of the mobile phase fluid, and can be described by a simple mathematical relationship. For a fixed operating temperature and outlet pressure, the temperature drop increases monotonically with the pressure drop.

  13. The bubble, drop and particle unit: A second-generation fluid physics facility

    NASA Astrophysics Data System (ADS)

    Kingdon, J.; Gonfalone, A.

    The objectives of the Bubble, Drop and Particle Unit (BDPU) can be summarised as follows: Investigation into hydrostatics, dynamics, thermodynamics, electrodynamics, and more generally the dynamics of two phase mixtures. As a middle course between dedicated autonomy and multi-purpose usage, a modular approach has been adopted that should allow assembly into `as required facilities' that can be reconfigured between flights to accommodate the mission's peculiar requirements of the investigators. The concept is centered around a service module which provides electronic control and monitoring data management, power supply, stimuli and diagnostic services. Interchangeable diagnostic modules will be available with a particular emphasis on the use of laser techniques.

  14. High Pressure, Transport Properties of Fluids: Theory and Data from Levitated Fluid-Drops at Combustion-Relevant Temperatures

    NASA Technical Reports Server (NTRS)

    Bellan, J.; Ohaska, K.

    2001-01-01

    The objective of this investigation is to derive a set of consistent mixing rules for calculating diffusivities and thermal diffusion factors over a thermodynamic regime encompassing the subcritical and supercritical ranges. These should serve for modeling purposes, and therefore for accurate simulations of high pressure phenomena such as fluid disintegration, turbulent flows and sprays. A particular consequence of this work will be the determination of effective Lewis numbers for supercritical conditions, thus enabling the examination of the relative importance of heat and mass transfer at supercritical pressures.

  15. Evaporation dynamics of non-spherical sessile drops of pure fluids and binary mixtures

    NASA Astrophysics Data System (ADS)

    Saenz, Pedro J.; Matar, Omar K.; Sefiane, Khellil; Valluri, Prashant; Kim, Jungho

    2015-11-01

    The dynamics of pure axisymmetric volatile sessile droplets have been meticulously examined over the last four decades but remain poorly understood. Studies focusing on more realistic non-spherical configurations are virtually non-existent. The dynamics of the latter are examined in this investigation by means of experiments and numerical simulations. We show that the lifetime and bulk flow characteristics of these drops depend on their size and shape. The irregular geometries lead to the emergence preferential convection currents in the liquid as well as differential local evaporation rates noticeable along the contact line. Similarly, we inspect the thermocapillary stability of the flow, which results as the liquid volatility increases, and find that this is also affected by the non-uniform wettability along the triple line. The Marangoni-driven instabilities grow in an intricate spatio-temporal fashion leading to the emergence of different flow regimes. Finally, we also provide new insights into the evaporation process of binary-mixture drops. Memphis Multiphase (EPSRC EP/K003976/1) & ThermaPOWER (EU IRSES-PIRSES GA-2011-294905).

  16. Evidence for the existence of an effective interfacial tension between miscible fluids: isobutyric acid-water and 1-butanol-water in a spinning-drop tensiometer.

    PubMed

    Pojman, John A; Whitmore, Colin; Turco Liveri, Maria Liria; Lombardo, Renato; Marszalek, Jolanta; Parker, Rosie; Zoltowski, Brian

    2006-03-14

    We report definitive evidence for an effective interfacial tension between two types of miscible fluids using spinning-drop tensiometry (SDT). Isobutyric acid (IBA) and water have an upper critical solution temperature (UCST) of 26.3 degrees C. We created a drop of the IBA-rich phase in the water-rich phase below the UCST and then increased the temperature above it. Long after the fluids have reached thermal equilibrium, the drop persists. By plotting the inverse of the drop radius cubed (r(-)(3)) vs the rotation rate squared (omega(2)), we confirmed that an interfacial tension exists and estimated its value. The transition between the miscible fluids remained sharp instead of becoming more diffuse, and the drop volume decreased with time. We observed droplet breakup via the Rayleigh-Tomotika instability above the UCST when the rotation rate was decreased by 80%, again demonstrating the existence of an effective interfacial tension. When pure IBA was injected into water above the UCST, drops formed inside the main drop even as the main drop decreased in volume with time. We also studied 1-butanol in water below the solubility limit. Effective interfacial tension values measured over time were practically constant, while the interface between the two phases remains sharp as the volume of the drop declines. The effective interfacial tension was found to be insensitive to changes in temperature and always larger than the equilibrium interfacial tension. Although these results may not apply to all miscible fluids, they clearly show that an effective interfacial tension can exist and be measured by SDT for some systems.

  17. Earthquake dynamics. Mapping pressurized volcanic fluids from induced crustal seismic velocity drops.

    PubMed

    Brenguier, F; Campillo, M; Takeda, T; Aoki, Y; Shapiro, N M; Briand, X; Emoto, K; Miyake, H

    2014-07-04

    Volcanic eruptions are caused by the release of pressure that has accumulated due to hot volcanic fluids at depth. Here, we show that the extent of the regions affected by pressurized fluids can be imaged through the measurement of their response to transient stress perturbations. We used records of seismic noise from the Japanese Hi-net seismic network to measure the crustal seismic velocity changes below volcanic regions caused by the 2011 moment magnitude (M(w)) 9.0 Tohoku-Oki earthquake. We interpret coseismic crustal seismic velocity reductions as related to the mechanical weakening of the pressurized crust by the dynamic stress associated with the seismic waves. We suggest, therefore, that mapping seismic velocity susceptibility to dynamic stress perturbations can be used for the imaging and characterization of volcanic systems.

  18. Efficacy of lodoxamide eye drops on tear fluid cytology of patients with vernal conjunctivitis.

    PubMed

    Oguz, H; Bitiren, M; Aslan, O S; Ozardali, I

    1999-06-01

    A double-masked, randomized, placebo-controlled study was conducted to evaluate the effectiveness of lodoxamide tromethamine 0.1% eyedrops in preventing inflammatory cell accumulation in the tear fluid of patients with vernal conjunctivitis. A 1-week baseline period was followed by 4 weeks of treatment with either lodoxamide tromethamine 0.1% ophthalmic solution or placebo in 30 symptomatic subjects with vernal conjunctivitis. Cytological evaluation of tear fluid was performed before and after the treatment. In the lodoxamide-treated group, but not in the placebo-treated group, the number of neutrophils (P = 0.051) and eosinophils (P = 0.020) in the tears significantly decreased at the end of 4 weeks when compared with baseline (Wilcoxon-signed rank test). It was concluded that lodoxamide treatment was significantly more effective than the placebo in terms of reducing inflammatory cells in the tear fluid in vernal conjunctivitis. This objective inhibition of inflammatory cells may be associated with clinical relief.

  19. Effects of pressure drop, particle size and thermal conditions on retention and efficiency in supercritical fluid chromatography.

    PubMed

    Poe, Donald P; Schroden, Jonathan J

    2009-11-06

    The effects of particle size and thermal insulation on retention and efficiency in packed-column supercritical fluid chromatography with large pressure drops are described for the separation of a series of model n-alkane solutes. The columns were 2.0mm i.d.x150mm long and were packed with 3, 5, or 10-mum porous octylsilica particles. Separations were performed with pure carbon dioxide at 50 degrees C at average mobile phase densities of 0.47g/mL (107bar) and 0.70g/mL (151bar). The three principal causes of band broadening were the normal dispersion processes described by the van Deemter equation, changes in the retention factor due to the axial density gradient, and radial temperature gradients associated with expansion of the mobile phase. At the lower density the use of thermal insulation resulted in significant improvements in efficiency and decreased retention times at large pressure drops. The effects are attributed to the elimination of radial temperature gradients and the concurrent enhancement of the axial temperature gradient. Thermal insulation had no significant effect on chromatographic performance at the higher density. A simple expression to predict the onset of excess efficiency loss due to the radial temperature gradient is proposed.

  20. Controlling the Mobility of the Fluid Interface of Moving Gas Bubbles or Liquid Drops by Using Micellar Solutions of Surfactants

    NASA Technical Reports Server (NTRS)

    Maldarelli, Charles; Papageorgiou, Demetrios

    1998-01-01

    Microgravity processes must rely on mechanisms other than buoyancy to move bubbles or droplets from one region to another in a continuous liquid phase. One suggested method is thermocapillary migration in which a temperature gradient is applied to the continuous phase. A significant and as yet unresolved impediment to the use of thermocapillary migration to direct bubble or drop motion is that these migrations can be significantly retarded by the adsorption onto the fluid particle surface of surface active impurities unavoidably present in the continuous or (if the particle is a liquid) droplet phases. The focus of our research was to develop a theory for remobilizing fluid particle interfaces retarded by a surfactant impurity in an effort to make more viable the use of thermocapillary migrations for the management of bubbles and drops in microgravity. We postulated that a surfactant at high bulk concentration which kinetically exchanges rapidly with the surface can restore interface mobility. The scaling arguments along with a discussion of the previous literature is reviewed in the context of the scaling framework. The specific objectives of the research were twofold. The first was to prove the remobilization theory by studying a model problem. As the mechanism for remobilization is independent of the force which drives the particle, the fluid particle shape and the presence of fluid inertia, we chose the simplest model consisting of a spherical bubble rising steadily by buoyancy in creeping flow. We solved the hydrodynamic and surfactant transport equations for rapid kinetic exchange to demonstrate that as the concentration increases, the Marangoni retardation at first increases (the low k behavior) and then decreases (the high k behavior). The second objective was to develop a method to determine the kinetic rate constants of a surfactant molecule, since this information is necessary to select surfactants which will exchange rapidly enough relative to the

  1. High-Speed Transport of Fluid Drops and Solid Particles via Surface Acoustic Waves

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph; Bao, Xiaoqi; Sherrit, Stewart; Badescu, Mircea; Lih, Shyh-shiuh

    2012-01-01

    A compact sampling tool mechanism that can operate at various temperatures, and transport and sieve particle sizes of powdered cuttings and soil grains with no moving parts, has been created using traveling surface acoustic waves (SAWs) that are emitted by an inter-digital transducer (IDT). The generated waves are driven at about 10 MHz, and it causes powder to move towards the IDT at high speed with different speeds for different sizes of particles, which enables these particles to be sieved. This design is based on the use of SAWs and their propelling effect on powder particles and fluids along the path of the waves. Generally, SAWs are elastic waves propagating in a shallow layer of about one wavelength beneath the surface of a solid substrate. To generate SAWs, a piezoelectric plate is used that is made of LiNbO3 crystal cut along the x-axis with rotation of 127.8 along the y-axis. On this plate are printed pairs of fingerlike electrodes in the form of a grating that are activated by subjecting the gap between the electrodes to electric field. This configuration of a surface wave transmitter is called IDT. The IDT that was used consists of 20 pairs of fingers with 0.4-mm spacing, a total length of 12.5 mm. The surface wave is produced by the nature of piezoelectric material to contract or expand when subjected to an electric field. Driving the IDT to generate wave at high amplitudes provides an actuation mechanism where the surface particles move elliptically, pulling powder particles on the surface toward the wavesource and pushing liquids in the opposite direction. This behavior allows the innovation to separate large particles and fluids that are mixed. Fluids are removed at speed (7.5 to 15 cm/s), enabling this innovation of acting as a bladeless wiper for raindrops. For the windshield design, the electrodes could be made transparent so that they do not disturb the driver or pilot. Multiple IDTs can be synchronized to transport water or powder over larger

  2. Retaining activity of enzymes after capture and extraction within a single-drop of biological fluid using immunoaffinity membranes.

    PubMed

    Shimazaki, Youji; Sato, Yuki

    2016-05-15

    The purpose of this study was the measurement of enzyme activity within a single-drop of biological fluid after micropurification. Esterase and lactate dehydrogenase (LDH) retained their enzymatic activities after being captured by membrane-immobilized antibodies, which were prepared by non-denaturing two-dimensional electrophoresis, transferred to polyvinylidene difluoride and then stained by Ponceau S. The activities of both enzymes were also measured after being captured by antibodies and biotinylated antibodies bound to membrane-immobilized protein A or avidin, respectively. After esterase and LDH were captured from biological samples by membrane-immobilized protein A or avidin, their activities were semi-quantitatively measured on the surface of the membrane using fluorescence determination. More than 51% of enzyme activities were retained even after the enzymes were captured by biotinylated antibody bound to membrane-immobilized avidin and eluted by rinsing with 5μL of 1% Triton X-100, compared with the activities of the enzyme on the immunoaffinity membrane.

  3. Strain response and re-equilibration of CH4-rich synthetic aqueous fluid inclusions in calcite during pressure drops

    NASA Astrophysics Data System (ADS)

    Bourdet, Julien; Pironon, Jacques

    2008-06-01

    Aqueous fluids in sedimentary basins often contain dissolved methane, particularly in petroleum environments. PVTX (Pressure-Volume-Temperature-Composition) reconstructions performed using fluid inclusion data are largely based on the assumption that inclusions do not change from the time of trapping until the present. Many authors, however, consider that fluid inclusions can re-equilibrate, particularly in fragile minerals like calcite. In order to understand this re-equilibration phenomenon in the metamorphic domain, previous experiments have been performed under high PT conditions, but few have been performed at low to medium PT conditions such as those associated with sedimentary burial diagenesis, and no previous studies have examined CH4-bearing aqueous inclusions in calcite. An experimental study of the preservation/modification of CH4-rich synthetic fluid inclusions in calcite during isothermal decompression was conducted. An autoclave was used for accurate PTX control allowing equilibrium between liquid and vapour in the CH4-H2O system. PTX conditions were maintained at four stages of decreasing pressure, with each stage held for 7 days to simulate an isothermal pressure drop. In order of decreasing pressure, the pressure-temperature conditions monitored were 276 ± 10 bar at 180 ± 7 °C, 176 ± 10 bar at 180 ± 7 °C, 76 ± 10 bar at 180 ± 7 °C and 10 ± 3 bar at 180 ± 15 °C. At the end of the experiment, the calcite was recovered and analyzed by microthermometry and Raman microspectroscopy for PTX reconstruction. A careful procedure was adopted to limit re-equilibration of inclusions during analytical procedures. Four types of inclusion shapes and four types of strain patterns were differentiated. Classification of the petrographic strain patterns was carried out. These strain patterns were associated with inclusion stretching and/or leakage regarding CH4, Th and Ph compared to experimental conditions. Factors controlling the preservation or

  4. Bidirectional Glenn shunt as an adjunct to surgical repair of congenital heart disease associated with pulmonary outflow obstruction: relevance of the fluid pressure drop-flow relationship.

    PubMed

    Ascuitto, Robert; Ross-Ascuitto, Nancy; Wiesman, Joshua; Deleon, Serafin

    2008-09-01

    A bidirectional Glenn shunt (BGS) was successfully incorporated into a two-ventricle repair for 10 patients (age, 3-17 years) who had congenital heart disease associated with severe pulmonary outflow obstruction. The BGS was used to volume-unload the pulmonary ventricle faced with residual outflow obstruction, thereby avoiding the need for insertion of a ventricle-to-pulmonary artery conduit. Transthoracic Doppler flow velocity analysis was used to determine transpulmonary peak systolic pressure drops as a measure of obstruction. Preoperative values ranged from 70 to 100 mmHg, and postoperative values ranged from less than 10 to 16 mmHg. At this writing, all patients are doing well 15 to 52 months after surgery. To gain further insight into the reduced pressure drop that may be achieved by decreasing flow rate across obstruction, a computer-based description of fluid flow was used to simulate blood traversing circumferentially narrowed passages. Overall pressure drops and associated flow energy losses were determined from numeric solutions (using finite-element analysis) to the Navier-Stokes equations for the proposed fluid reactions. Pressure drops and flow energy losses were found to decrease dramatically as flow rate was progressively reduced. For selected patients, a BGS can be an effective adjunct to the surgical treatment of pulmonary outflow obstruction. This approach avoids the use of a ventricle-to-pulmonary artery conduit, and thus the inevitable need in most patients for reoperations because of somatic growth, conduit failure, or both.

  5. Steady axisymmetric motion of deformable drops falling or rising through a homoviscous fluid in a tube at intermediate Reynolds number

    NASA Astrophysics Data System (ADS)

    Bozzi, Lloyd A.; Feng, James Q.; Scott, Timothy C.; Pearlstein, Arne J.

    1997-04-01

    The steady axisymmetric flow in and around a deformable drop moving under the action of gravity along the axis of a vertical tube at intermediate Reynolds number is studied by solving the nonlinear free-boundary problem using a Galerkin finite-element method. For the case where the drop and suspending liquid have the same viscosity, the ratio of the densities is 6/5 or 5/6, and the radius of the tube is equal to twice the radius of a sphere having the drop volume, four significant results are apparent in the computations. First, we compute drops showing much more deformation, and in particular the development of considerably more non-convexity, than those found in previous calculations for non-zero Reynolds number. The degree of non-convexity typically grows with the Reynolds number. Secondly, external recirculation zones can be attached to or disjoint from the drop. We find when there is a single external recirculation zone, that is disjoint (as found by Dandy & Leal), it can attach to the drop as the Reynolds number is increased. As the Reynolds number further increases, this is immediately followed by division of the drop into two adjacent recirculating regions. Thirdly, we sometimes find two recirculation zones in the suspending liquid. Finally, the drag coefficient, axis ratio, and normalized interfacial and frontal areas of the drop can vary non-monotonically with the Weber number, exhibiting as many as four local extrema. The results are compared to previous theoretical and experimental work, and implications for drop motion and heat and mass transfer are discussed.

  6. Heat transfer and pressure drop characteristics of a plate heat exchanger using a propylene-glycol/water mixture as the working fluid

    SciTech Connect

    Talik, A.C.; Fletcher, L.S.; Anand, N.K.; Swanson, L.W.

    1995-12-31

    Plate heat exchangers are becoming increasingly important because of their potential applications in industrial processes, especially in terms of their thermal performance and their limited pressure drop. An experimental investigation to acquire both heat-transfer and pressure-drop data for a plate heat exchanger was conducted in order to respond to these interests. A propylene-glycol/water mixture was used as the working fluid in order to provide lower Reynolds numbers than those provided by water at similar test conditions. The plate heat exchanger was composed of 31 plates, each with a chevron angle of 30 degrees. The isothermal pressure drop data were taken in the fully laminar flow regime for Reynolds numbers from 10 to 80. The heat transfer data were taken in the fully laminar flow regime for Reynolds numbers of 80 to 720 with heat transfer rates of 1.1 {times} 10{sup 5} to 6.5 {times} 10{sup 5} W. The experimental data for the friction factor and Nusselt number were correlated using a standard power-law function. Other published heat-transfer and friction factor correlations for plate heat exchangers with similar plates at selected conditions are compared to the data.

  7. Modelling flow and heat transfer in two-fluid interfacial flows, with applications to drops and jets

    NASA Astrophysics Data System (ADS)

    Mehdi-Nejad, Vala

    2003-10-01

    A two-dimensional, axi-symmetric model is developed to calculate flow and heat transfer in a two-fluid system. The model uses one set of the governing equations combined with a volume tracking method on a fixed structured mesh to model the simultaneous movement of mass, momentum and energy across cell boundaries. Both first and second-order methods are used to approximate temperature fields with sharp gradients that exist near a fluid-fluid interface. The model is first used to simulate the effect of surrounding air during a droplet impact. Bubble entrapment is observed in both numerical simulation and experimental photographs. The impact of water, n-heptane and molten nickel droplets on a solid surface is simulated. When a droplet approaches another surface, air in the gap between them was forced out. Increased air pressure below the droplet creates a depression in its surface, in which air is trapped. Different behaviors observed for water and n-heptane simulations are attributed to differences in wetting behavior. Next, to demonstrate the capabilities of the model, the interfacial heat transfer from molten tin droplets falling in an oil bath is modelled. The development of vortices behind droplets is simulated and the effect of fluid recirculation and oil thermal conductivity on heat dissipation is studied. The thesis concludes with application of the model to a study of interfacial heat transfer during jet break up. It is demonstrated that the change of fluid properties associated with interfacial heat transfer affects the jet break up and the resulting droplet size. It is also shown that obtaining a desirable droplet size during jet break up not only depends on hydrodynamic conditions such as nozzle diameter, jet initial velocity, and pressure, but also on thermal conditions such as the initial jet temperature and the surrounding fluid thermal properties.

  8. Gas Pressure-Drop Experiment

    ERIC Educational Resources Information Center

    Luyben, William L.; Tuzla, Kemal

    2010-01-01

    Most chemical engineering undergraduate laboratories have fluid mechanics experiments in which pressure drops through pipes are measured over a range of Reynolds numbers. The standard fluid is liquid water, which is essentially incompressible. Since density is constant, pressure drop does not depend on the pressure in the pipe. In addition, flow…

  9. Universal phase and force diagrams for a microbubble or pendant drop in static fluid on a surface

    NASA Astrophysics Data System (ADS)

    Wei, P. S.; Hsiao, C. C.; Chen, K. Y.

    2008-01-01

    Dimensionless three-dimensional universal phase and lift force diagrams of a microbubble (or pendant drop) in static liquid on a solid surface (or orifice) are presented in this work. Microbubble dynamics has been found to play a vital role in mass, momentum, energy, and concentration transfer rates in contemporary micro- and nanosciences and technologies. In this study, dimensionless phase and force diagrams are introduced by utilizing the analytical solutions of the microbubble shape reported in the literature. It shows that phase and force diagrams can be universally specified by two dimensionless independent parameters, Bond number, and contact angle (or base radius). Based on the presence of an inflection point or neck on the microbubble surface, each diagram exhibits three regions. Growth, detachment, and entrapment of a microbubble can be described by path lines in three regions. The corresponding universal total lift forces include hydrostatic buoyancy, difference in gas, and hydrostatic pressures at the base, capillary pressure, as well as surface tension induced by the variation of circumference, which has not been treated in the literature so far. In the absence of viscous stress and Marangoni force, the total lift force equals surface tension induced by the variation of circumference. The latter can be an attaching or lifting force, depending on whether the state in the distinct regions and contact angle is less than or greater than a critical angle. The critical angle, which is slightly less than the inclination angle at the inflection point, is decreased with increasing Bond number.

  10. Drop in transforming growth factor-alpha and osteoprotegerin level in gingival crevicular fluid from patients with gingivitis.

    PubMed

    Otogoto, Junichi; Mogi, Makio

    2009-01-01

    Inflammatory mediators, especially cytokine, play a central role in the pathogenesis of gingivitis. The aim of this study was to identify and quantify the various growth factors, and cytokines in the gingival crevicular fluid (GCF) of patients with gingivitis, as compared with those of control subjects. The levels of cytokine in the samples were determined by their respective ELISAs. The transforming growth factor (TGF)-alpha and osteoprotegerin (OPG) level were significantly lower in patients with gingivitis than in the controls (p < 0.05). Also, there was a positive correlation between TGF-alpha and OPG levels (r = 0.761). These results suggest that the decrease in growth factor TGF-alpha is associated with the pathophysiology and/or the progress of gingivitis.

  11. Drag on Sessile Drops

    NASA Astrophysics Data System (ADS)

    Milne, Andrew J. B.; Fleck, Brian; Nobes, David; Sen, Debjyoti; Amirfazli, Alidad; University of Alberta Mechanical Engineering Collaboration

    2013-11-01

    We present the first ever direct measurements of the coefficient of drag on sessile drops at Reynolds numbers from the creeping flow regime up to the point of incipient motion, made using a newly developed floating element differential drag sensor. Surfaces of different wettabilities (PMMA, Teflon, and a superhydrophobic surface (SHS)), wet by water, hexadecane, and various silicone oils, are used to study the effects of drop shape, and fluid properties on drag. The relation between drag coefficient and Reynolds number (scaled by drop height) varies slightly with liquid-solid system and drop volume with results suggesting the drop experiences increased drag compared to similar shaped solid bodies due to drop oscillation influencing the otherwise laminar flow. Drops adopting more spherical shapes are seen to experience the greatest force at any given airspeed. This indicates that the relative exposed areas of drops is an important consideration in terms of force, with implications for the shedding of drops in applications such as airfoil icing and fuel cell flooding. The measurement technique used in this work can be adapted to measure drag force on other deformable, lightly adhered objects such as dust, sand, snow, vesicles, foams, and biofilms. The authours acknowledge NSERC, Alberta Innovates Technology Futures, and the Killam Trusts.

  12. Single-drop liquid-phase microextraction for the determination of hypericin, pseudohypericin and hyperforin in biological fluids by high performance liquid chromatography.

    PubMed

    Gioti, Eleni M; Skalkos, Dimitris C; Fiamegos, Yiannis C; Stalikas, Constantine D

    2005-11-04

    The analysis of hypericin, pseudohypericin (collectively called in this study hypericins) and hyperforin in biological fluids is reported using single-drop liquid-phase microextraction in conjunction with HPLC-UV-fluorescence detection. A new option for analysis of the active principle constituents in biological samples is proposed, reducing the steps required prior to analysis. There are several parameters which determine the mass transfer such as the extraction solvent, drop and sample volumes, extraction time and temperature, pH and ionic strength, stirring rate and depth of needle tip in the bulk solution. These parameters were chosen to optimize the performance in the current study. The method was validated with respect to precision, accuracy and specificity. The intra-day precision values were below 2.3% for the high concentration level of control samples and 6.2% for the low level. The respective inter-day precision values were calculated to be below 4.4 and 7.1%, respectively, for the two concentration levels. Accuracy of the method, calculated as relative error, ranged from -2.6 to 7.0%. It was demonstrated that as long as the extraction procedure is consistently applied, quantitative analysis is performed accurately and reproducibly in human urine and plasma samples. Limits of quantitation (LOQs) in urine were calculated to be 3, 6 and 12 ng/ml for pseudohypericin, hypericin and hyperforin, respectively. Slightly higher limits were measured in plasma, i.e. 5, 12 and 20 ng/ml, for the respective analytes.

  13. Laminar flow heat transfer and pressure drop characteristics of power-law fluids inside tubes with varying width twisted tape inserts

    SciTech Connect

    Patil, A.G.

    2000-02-01

    Results of an experimental investigation of heat transfer and flow friction of a generalized power-law fluid in tape generated swirl flow inside a 25.0 mm i.d. circular tube, are presented. In order to reduce excessive pressure drops associated with full width twisted tapes, with less corresponding reduction in heat transfer coefficients, reduced width twisted tapes of widths ranging from 11.0 to 23.8 mm, which are lower than the tube inside diameter are used. Reduced width twisted tape inserts give 18%--56% lower isothermal friction factors than the full width tapes. Uniform wall temperature Nusselt numbers decrease only slightly by 5%--25%, for tape widths of 19.7 and 11.0 mm, respectively. Based on the constant pumping power criterion, the tapes of width 19.7 mm perform more or less like full width tapes. Correlations are presented for isothermal and heating friction factors and Nusselt numbers (under uniform wall temperature condition) for a fully developed laminar swirl flow, which are applicable to full width as well as reduced width twisted tapes, using a modified twist ratio as pitch to width ratio of the tape. The reduced width tapes offer 20%--50% savings in the tape material as compared to the full width tapes.

  14. Influence of the fluid structure on the binding potential: Comparing liquid drop profiles from density functional theory with results from mesoscopic theory.

    PubMed

    Hughes, Adam P; Thiele, Uwe; Archer, Andrew J

    2017-02-14

    For a film of liquid on a solid surface, the binding potential g(h) gives the free energy as a function of the film thickness h and also the closely related (structural) disjoining pressure Π=-∂g/∂h. The wetting behaviour of the liquid is encoded in the binding potential and the equilibrium film thickness corresponds to the value at the minimum of g(h). Here, the method we developed in the work of Hughes et al. [J. Chem. Phys. 142, 074702 (2015)], and applied with a simple discrete lattice-gas model, is used with continuum density functional theory (DFT) to calculate the binding potential for a Lennard-Jones fluid and other simple liquids. The DFT used is based on fundamental measure theory and so incorporates the influence of the layered packing of molecules at the surface and the corresponding oscillatory density profile. The binding potential is frequently input in mesoscale models from which liquid drop shapes and even dynamics can be calculated. Here we show that the equilibrium droplet profiles calculated using the mesoscale theory are in good agreement with the profiles calculated directly from the microscopic DFT. For liquids composed of particles where the range of the attraction is much less than the diameter of the particles, we find that at low temperatures g(h) decays in an oscillatory fashion with increasing h, leading to highly structured terraced liquid droplets.

  15. Influence of the fluid structure on the binding potential: Comparing liquid drop profiles from density functional theory with results from mesoscopic theory

    NASA Astrophysics Data System (ADS)

    Hughes, Adam P.; Thiele, Uwe; Archer, Andrew J.

    2017-02-01

    For a film of liquid on a solid surface, the binding potential g(h) gives the free energy as a function of the film thickness h and also the closely related (structural) disjoining pressure Π =-∂g /∂h . The wetting behaviour of the liquid is encoded in the binding potential and the equilibrium film thickness corresponds to the value at the minimum of g(h). Here, the method we developed in the work of Hughes et al. [J. Chem. Phys. 142, 074702 (2015)], and applied with a simple discrete lattice-gas model, is used with continuum density functional theory (DFT) to calculate the binding potential for a Lennard-Jones fluid and other simple liquids. The DFT used is based on fundamental measure theory and so incorporates the influence of the layered packing of molecules at the surface and the corresponding oscillatory density profile. The binding potential is frequently input in mesoscale models from which liquid drop shapes and even dynamics can be calculated. Here we show that the equilibrium droplet profiles calculated using the mesoscale theory are in good agreement with the profiles calculated directly from the microscopic DFT. For liquids composed of particles where the range of the attraction is much less than the diameter of the particles, we find that at low temperatures g(h) decays in an oscillatory fashion with increasing h, leading to highly structured terraced liquid droplets.

  16. Drop dynamics

    NASA Technical Reports Server (NTRS)

    Elleman, D. D.

    1981-01-01

    The drop dynamics module is a Spacelab-compatible acoustic positioning and control system for conducting drop dynamics experiments in space. It consists basically of a chamber, a drop injector system, an acoustic positioning system, and a data collection system. The principal means of collecting data is by a cinegraphic camera. The drop is positioned in the center of the chamber by forces created by standing acoustic waves generated in the nearly cubical chamber (about 12 cm on a side). The drop can be spun or oscillated up to fission by varying the phse and amplitude of the acoustic waves. The system is designed to perform its experiments unattended, except for start-up and shutdown events and other unique events that require the attention of the Spacelab payload specialist.

  17. Pressure Drop

    NASA Technical Reports Server (NTRS)

    Lawson, Mike

    2010-01-01

    Mike Lawson briefly discussed pressure drop for aerospace applications and presented short stories about adventures experienced while working at NASA and General Dynamics, including exposure to technologies like the Crew and Equipment Translation Aid (CETA) cart and the SWME.

  18. Numerical study of the 3D-shape of a drop immersed in a fluid under an elongational flow with vorticity

    NASA Astrophysics Data System (ADS)

    Sanjuan, A. S.; Reyes, M. A. H.; Minzoni, A. A.; Geffroy, E.

    2017-01-01

    This work focuses on a three-dimensional analysis of the deformation of a drop — immersed in a Newtonian fluid— generated by a 2D elongational flow with vorticity. The study of steady-state deformations of the cross-section of the drop shows a prevalent non-circular shape. The axisymmetric idealization of the ellipsoid is not observed nor the linear dependency between capillary number and deformation of the drop, as Taylor and Cox theory predicted. Our numerical results are consistent with experiments and other numerical simulations. However, in the latter cases, measurements of the cross section of the drop are few while a limited class of flows is applied. In this work, deformations induced by general two-dimensional flows upon the 3D drop shape are presented with special emphasis about the length scale along the third axis —perpendicular to the plane of the applied flow field.

  19. Pressure, temperature and density drops along supercritical fluid chromatography columns in different thermal environments. III. Mixtures of carbon dioxide and methanol as the mobile phase.

    PubMed

    Poe, Donald P; Veit, Devon; Ranger, Megan; Kaczmarski, Krzysztof; Tarafder, Abhijit; Guiochon, Georges

    2014-01-03

    The pressure, temperature and density drops along SFC columns eluted with a CO2/methanol mobile phase were measured and compared with theoretical values. For columns packed with 3- and 5-μm particles the pressure and temperature drops were measured using a mobile phase of 95% CO2 and 5% methanol at a flow rate of 5mL/min, at temperatures from 20 to 100°C, and outlet pressures from 80 to 300bar. The density drop was calculated based on the temperature and pressure at the column inlet and outlet. The columns were suspended in a circulating air bath, either bare or covered with foam insulation. The experimental measurements were compared to theoretical results obtained by numerical simulation. For the convective air condition at outlet pressures above 100bar the average difference between the experimental and calculated temperature drops and pressure drops were 0.1°C and 0.7% for the bare 3-μm column, respectively, and were 0.6°C and 4.1% for the insulated column. The observed temperature drops for the insulated columns are consistent with those predicted by the Joule-Thomson coefficients for isenthalpic expansion. The dependence of the temperature and the pressure drops on the Joule-Thomson coefficient and kinematic viscosity are described for carbon dioxide mobile phases containing up to 20% methanol.

  20. Proceedings of the Second International Colloquium on Drops and Bubbles

    NASA Technical Reports Server (NTRS)

    Lecroissette, D. H. (Editor)

    1982-01-01

    Applications of bubble and drop technologies are discussed and include: low gravity manufacturing, containerless melts, microballoon fabrication, ink printers, laser fusion targets, generation of organic glass and metal shells, and space processing. The fluid dynamics of bubbles and drops were examined. Thermomigration, capillary flow, and interfacial tension are discussed. Techniques for drop control are presented and include drop size control and drop shape control.

  1. Drying drops of blood

    NASA Astrophysics Data System (ADS)

    Brutin, David; Sobac, Benjamin; Loquet, Boris; Sampol, José.

    2010-11-01

    The drying of a drop of human blood is fascinating by the complexity of the physical mechanisms that occur as well as the beauty of the phenomenon which has never been previously evidenced in the literature. The final stage of full blood evaporation reveals for a healthy person the same regular pattern with a good reproducibility. Other tests on anemia and hyperlipidemic persons were performed and presented different patterns. By means of digital camera, the influence of the motion of red blood cells (RBCs) which represent about 50% of the blood volume, is revealed as well as its consequences on the final stages of drying. The mechanisms which lead to the final pattern of dried blood drops are presented and explained on the basis of fluid and solid mechanics in conjunction with the principles of hematology. Our group is the first to evidence that the specific regular patterns characteristic of a healthy individual do not appear in a dried drop of blood from a person with blood disease. Blood is a complex colloidal suspension for which the flow motion is clearly non-Newtonian. When drops of blood evaporate, all the colloids are carried by the flow motion inside the drop and interact.

  2. Critical point wetting drop tower experiment

    NASA Technical Reports Server (NTRS)

    Kaulker, William F.

    1988-01-01

    Experiments with the wetting behavior of immiscible fluids against the container below the critical temperature are being performed in the MSFC Drop Tower Facility. Microgravity conditions extending up to three seconds (of the 4.5 second drop) are generated for the experiment. Specimens consist of glass cylindrical ampoules partially filled with fluid phases. How the fluids develop the meniscus geometry as well as hot the fluid interfaces respond to the microgravity induced oscillations is recorded during the experiment with on-board cameras. Drops are made at various temperatures to determine the interfacial energy variation as a function of temperature.

  3. Large amplitude drop shape oscillations

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.; Wang, T. G.

    1982-01-01

    An experimental study of large amplitude drop shape oscillation was conducted in immiscible liquids systems and with levitated free liquid drops in air. In liquid-liquid systems the results indicate the existence of familiar characteristics of nonlinear phenomena. The resonance frequency of the fundamental quadrupole mode of stationary, low viscosity Silicone oil drops acoustically levitated in water falls to noticeably low values as the amplitude of oscillation is increased. A typical, experimentally determined relative frequency decrease of a 0.5 cubic centimeters drop would be about 10% when the maximum deformed shape is characterized by a major to minor axial ratio of 1.9. On the other hand, no change in the fundamental mode frequency could be detected for 1 mm drops levitated in air. The experimental data for the decay constant of the quadrupole mode of drops immersed in a liquid host indicate a slight increase for larger oscillation amplitudes. A qualitative investigation of the internal fluid flows for such drops revealed the existence of steady internal circulation within drops oscillating in the fundamental and higher modes. The flow field configuration in the outer host liquid is also significantly altered when the drop oscillation amplitude becomes large.

  4. Hanging drop crystal growth apparatus

    NASA Technical Reports Server (NTRS)

    Naumann, Robert J. (Inventor); Witherow, William K. (Inventor); Carter, Daniel C. (Inventor); Bugg, Charles E. (Inventor); Suddath, Fred L. (Inventor)

    1990-01-01

    This invention relates generally to control systems for controlling crystal growth, and more particularly to such a system which uses a beam of light refracted by the fluid in which crystals are growing to detect concentration of solutes in the liquid. In a hanging drop apparatus, a laser beam is directed onto drop which refracts the laser light into primary and secondary bows, respectively, which in turn fall upon linear diode detector arrays. As concentration of solutes in drop increases due to solvent removal, these bows move farther apart on the arrays, with the relative separation being detected by arrays and used by a computer to adjust solvent vapor transport from the drop. A forward scattering detector is used to detect crystal nucleation in drop, and a humidity detector is used, in one embodiment, to detect relative humidity in the enclosure wherein drop is suspended. The novelty of this invention lies in utilizing angular variance of light refracted from drop to infer, by a computer algorithm, concentration of solutes therein. Additional novelty is believed to lie in using a forward scattering detector to detect nucleating crystallites in drop.

  5. Investigations of levitated helium drops

    NASA Astrophysics Data System (ADS)

    Whitaker, Dwight Lawrence

    1999-11-01

    We report on the development of two systems capable of levitating drops of liquid helium. Helium drops of ˜20 mum have been levitated with the radiation pressure from two counter-propagating Nd:YAG laser beams. Drops are produced with a submerged piezoelectric transducer, and could be held for up to three minutes in our optical trap. Calculations show that Brillouin and Raman scattering of the laser light in the liquid helium produces a negligible rate of evaporation of the drop. Evaporation caused by the enhanced vapor pressure of the curved drop surfaces appears to be a significant effect limiting the drop lifetimes. Helium drops as large as 2 cm in diameter have been suspended in the earth's gravitational field with a magnetic field. A commercial superconducting solenoid provides the necessary field, field-gradient product required to levitate the drops. Drops are cooled to 0.5 K with a helium-3 refrigerator, and can be held in the trap indefinitely. We have found that when two or more drops are levitated in the same magnetic trap, the drops often remain in a state of apparent contact without coalescing. This effect is a result of the evaporation of liquid from between the two drops, and is found to occur only for normal fluid drops. We can induce shape oscillations in charged, levitated drops with an applied ac electric field. We have measured the resonance frequencies and damping rates for the l = 2 mode of oscillation as function of temperature. We have also developed a theory to describe the small amplitude shape oscillations of a He II drop surrounded by its saturated vapor. In our theory, we have considered two sets of boundary conditions---one where the drop does not evaporate and another in which the liquid and vapor are in thermodynamic equilibrium. We have found that both solutions give a frequency that agrees well with experiment, but that the data for the damping rate agree better with the solution without evaporation.

  6. Exploding Water Drops

    NASA Astrophysics Data System (ADS)

    Reich, Gary

    2016-01-01

    Water has the unusual property that it expands on freezing, so that ice has a specific gravity of 0.92 compared to 1.0 for liquid water. The most familiar demonstration of this property is ice cubes floating in a glass of water. A more dramatic demonstration is the ice bomb shown in Fig. 1. Here a cast iron flask is filled with water and tightly stoppered. The flask is then cooled, either by leaving it outdoors in winter or by immersing it in a cryogenic fluid, until the water freezes. As the water freezes and expands, the pressure inside the flask increases dramatically, eventually becoming sufficient to fracture the metal walls of the enclosure. A related, but much less familiar, phenomenon is the explosive fracturing of small water drops upon freezing. That water drops can fracture in this way has been known for many years, and the phenomenon has been described in detail in the atmospheric sciences literature, where it is seen as relevant to the freezing of raindrops as they fall through cold air. Carefully controlled experiments have been done documenting how the character and frequency of fracture is affected by such variables as drop size, rate of cooling, chemistry of dissolved gases, etc. Here I describe instead a simple demonstration of fracture suitable for video analysis and appropriate for study at the introductory physics level. Readers may also be interested in other characteristics of freezing and fragmenting water drops, for example, charge separation upon fracture and the appearance of spikes and bulges on the surface.

  7. Shapes of Bubbles and Drops in Motion.

    ERIC Educational Resources Information Center

    O'Connell, James

    2000-01-01

    Explains the shape distortions that take place in fluid packets (bubbles or drops) with steady flow motion by using the laws of Archimedes, Pascal, and Bernoulli rather than advanced vector calculus. (WRM)

  8. Influence of aqueous electrolytes on the wetting behavior of hydrophobic solid polymers-low-rate dynamic liquid/fluid contact angle measurements using axisymmetric drop shape analysis.

    PubMed

    Welzel, Petra B; Rauwolf, Cordula; Yudin, Olexandr; Grundke, Karina

    2002-07-01

    The interaction of inorganic ions with low-energy hydrophobic surfaces was examined using model systems of solid polymers without ionizable functional surface groups in aqueous electrolyte solutions. Low-rate dynamic contact angle measurements with captive bubbles in conjunction with axisymmetric drop shape analysis (ADSA) were performed to study the influence of electrolyte ions (in the aqueous test solutions) on the wettability of the polymers. When various types of ions were used, no significant change in advancing and receding contact angles was observed. The contact angle hysteresis was small. The zeta potential of the model polymers in aqueous electrolyte solutions was determined from streaming potential measurements. The variation of the zeta potential at different pH levels indicates preferential adsorption of hydroxyl ions at this interface. However, the presence of electrolytes at the interface between water and the different model polymers did not influence the macroscopic contact angle. The results may suggest the absence of any specific interaction between the ions and the solid polymer, as this should result in changes of hydrophobicity. Similar to the air/water interface, the composition and the potential of the polymer/water interface are obviously determined predominantly by the aqueous phase with only slight influence from the solid phase.

  9. Electrohydrodynamics of a particle-covered drop

    NASA Astrophysics Data System (ADS)

    Ouriemi, Malika; Vlahovska, Petia

    2014-11-01

    We study the dynamics of a drop nearly-completely covered with a particle monolayer in a uniform DC electric field. The weakly conducting fluid system consists of a silicon oil drop suspended in castor oil. A broad range of particle sizes, conductivities, and shapes is explored. In weak electric fields, the presence of particles increases drop deformation compared to a particle-free drop and suppresses the electrohydrodynamic flow. Very good agreement is observed between the measured drop deformation and the small deformation theory derived for surfactant-laden drops (Nganguia et al., 2013). In stronger electric fields, where drops are expected to undergo Quincke rotation (Salipante and Vlahovska, 2010), the presence of the particles greatly decreases the threshold for rotation and the stationary tilted drop configuration observed for clean drop is replaced by a spinning drop with either a wobbling inclination or a very low inclination. These behaviors resemble the predicted response of rigid ellipsoids in uniform electric fields. At even stronger electric fields, the particles can form dynamic wings or the drop implodes. The similar behavior of particle-covered and surfactant-laden drops provides new insights into understanding stability of Pickering emulsions. Supported by NSF-CBET 1437545.

  10. Dilating Eye Drops

    MedlinePlus

    ... Frequently Asked Questions Español Condiciones Chinese Conditions Dilating Eye Drops En Español Read in Chinese What are dilating eye drops? Dilating eye drops contain medication to enlarge ( ...

  11. Investigation of drop coalescence using tomographic PIV

    NASA Astrophysics Data System (ADS)

    Ortiz-Duenas, Cecilia; Kim, Jungyong; Longmire, Ellen

    2008-11-01

    High-speed tomographic PIV was used to obtain evolving volumetric velocity fields of the coalescence of single drops and two side-by-side drops through liquid/liquid interfaces. Reynolds numbers (Re=ρsUσD/μs) based on surface tension velocity (Uσ=D/tσ) and surrounding ambient fluid were 8-10, and the viscosity ratio between the fluid drop and surrounding fluid was 0.14. The coalescence process investigated is driven by gravity and thus the initial drops are non-spherical and the interface is deformed by the drops. Previously, Mohamed-Kassim & Longmire (2004) showed that under these conditions, the film rupture typically occurs off-axis, and therefore the flow is three-dimensional. For a single drop, volumetric velocity vector fields are used to characterize the asymmetric film rupture occurring for 0drop into a vortex ring are relatively axisymmetric. For two side-by-side drops, the first drop to coalesce ruptures off-axis on the side closest to the second drop. The volumetric velocity and vorticity fields indicate an asymmetric collapse of the drop for 0.1drop while the capillary waves are axisymmetric.

  12. Characterization of maleic acid/anhydride copolymer films by low-rate dynamic liquid-fluid contact angle measurements using axisymmetric drop shape analysis.

    PubMed

    Uhlmann, Petra; Skorupa, Sebastian; Werner, Carsten; Grundke, Karina

    2005-07-05

    Thin films of alternating maleic acid/anhydride copolymers (poly(octadecene-alt-maleic acid/anhydride), POMA; poly(propene-alt-maleic acid/anhydride), PPMA; poly(styrene-alt-maleic acid/anhydride), PSMA) were studied to unravel the influence of the comonomer characteristics in the backbone on the surface-energetic properties of the copolymer films in the dry state and in contact with aqueous solutions. Water contact angle measurements revealed a graduation of the wettability of the dry hydrolyzed and annealed copolymer films that was dependent on the comonomer unit. It ranged from moderately hydrophilic (PPMA, annealed gamma(sv) = 39.9 mJ/m2) to very hydrophobic (POMA, annealed, gamma(sv) = 18.4 mJ/m2) surfaces. Liquid-fluid contact angle measurements using captive air bubbles were performed in different aqueous media (pure water, phosphate-buffered saline, and 10(-)(3) M KCl of two different pH values (pH = 3 and pH = 10) to study the copolymer films in their hydrated states relevant for biointerfacial phenomena. It was found that the graduation of the wettability of the copolymer films in the dry state is overall maintained upon immersion in aqueous solutions. The dependence of the wettability on the pH value of the aqueous medium could be related to the (de)protonation of the carboxylic groups.

  13. Head-on collision of drops: A numerical investigation

    NASA Technical Reports Server (NTRS)

    Nobari, M. R.; Jan, Y.-J.; Tryggvason, G.

    1993-01-01

    The head-on collision of equal sized drops is studied by full numerical simulations. The Navier-Stokes equations are solved for fluid motion both inside and outside the drops using a front tracking/finite difference technique. The drops are accelerated toward each other by a body force that is turned off before the drops collide. When the drops collide, the fluid between them is pushed outward leaving a thin later bounded by the drop surface. This layer gets progressively thinner as the drops continue to deform and in several of the calculations this double layer is artificially removed once it is thin enough, thus modeling rupture. If no rupture takes place, the drops always rebound, but if the film is ruptured the drops may coalesce permanently or coalesce temporarily and then split again.

  14. A Different Cone: Bursting Drops in Solids

    NASA Astrophysics Data System (ADS)

    Zhao, Xuanhe

    2013-03-01

    Drops in fluids tend to be spheres--a shape that minimizes surface energy. In thunderstorm clouds, drops can become unstable and emit thin jets when charged beyond certain limits. The instability of electrified drops in gases and liquids has been widely studied and used in applications including ink-jet printing, electrospinning nano-fibers, microfluidics and electrospray ionization. Here we report a different scenario: drops in solids become unstable and burst under sufficiently high electric fields. We find the instability of drops in solids morphologically resembles that in liquids, but the critical electric field for the instability follows a different scaling due to elasticity of solids. Our observations and theoretical models not only advance the fundamental understanding of electrified drops but also suggest a new failure mechanism of high-energy-density dielectric polymers, which have diverse applications ranging from capacitors for power grids and electric vehicles to muscle-like transducers for soft robots and energy harvesting.

  15. Coalescence of a Drop inside another Drop

    NASA Astrophysics Data System (ADS)

    Mugundhan, Vivek; Jian, Zhen; Yang, Fan; Li, Erqiang; Thoroddsen, Sigurdur

    2016-11-01

    Coalescence dynamics of a pendent drop sitting inside another drop, has been studied experimentally and in numerical simulations. Using an in-house fabricated composite micro-nozzle, a smaller salt-water drop is introduced inside a larger oil drop which is pendent in a tank containing the same liquid as the inner drop. On touching the surface of outer drop, the inner drop coalesces with the surrounding liquid forming a vortex ring, which grows in time to form a mushroom-like structure. The initial dynamics at the first bridge opening up is quantified using Particle Image Velocimetry (PIV), while matching the refractive index of the two liquids. The phenomenon is also numerically simulated using the open-source code Gerris. The problem is fully governed by two non-dimensional parameters: the Ohnesorge number and the diameter ratios of the two drops. The validated numerical model is used to better understand the dynamics of the phenomenon. In some cases a coalescence cascade is observed with liquid draining intermittently and the inner drop reducing in size.

  16. Thermocapillary Migration and Interactions of Bubbles and Drops

    NASA Technical Reports Server (NTRS)

    Balasubramaniam, R.; Lacy, Claud E.; Wozniak, Guenter; Subramanian, R. Shankar

    1996-01-01

    When a drop or bubble is placed in another fluid and subjected to the action of a temperature gradient, the drop will move. Such motion is a direct consequence of the variation of interfacial tension with temperature, and is termed thermocapillary migration. This paper discusses results from experiments conducted in reduced gravity on the thermocapillary motion of bubbles and drops.

  17. Characteristics of Unequal Size Drop Collisions

    NASA Astrophysics Data System (ADS)

    Kim, Jungyong; Longmire, Ellen; Kim, Man Sik

    2009-11-01

    Pairs of water/glycerin drops were injected into silicone oil and traveled on downward trajectories before colliding. Unequal size drop collisions with drop size ratios (Ds/DL) of 0.7 and 0.5 were investigated. Simultaneous dual-field PIV measurements were obtained to characterize coalescence and rebounding behavior. The initial injection angle and tube height were adjusted to access appropriate impact parameters. In the current study, the collision angle of the large drop was, in general, shallower than that of the small drop, and a range of velocity ratios and impact parameters was examined. Coalescence occurs above We* = 11 similar to collision outcomes for equal size drops. As drop size ratio decreases, the intervening film deforms more. If the velocity ratio uL/us < 1, the interface remains deformed at coalescence, but if uL/us > 1, the interface flattens before coalescence. The rupture location varies due to the asymmetry of the drops. As collision offset increases (B > 0), the film rupture time is shortened and mixing of the fluid within the drops is enhanced after coalescence. These results will be compared with the behavior observed previously for equal size drop collisions.

  18. Method and apparatus for producing drops using a drop-on-demand dispenser

    DOEpatents

    Chen, Alvin U.; Basaran, Osman A.

    2003-01-01

    A method and apparatus for dispensing fluid from a drop-on-demand (DOD) fluid dispenser. The method involves withdrawing fluid in the dispenser for a first duration of time, followed by a second duration of time during which the fluid is propelled toward the orifice of the dispenser. Following the period during which the fluid is propelled, there is a second withdrawing of the fluid into the dispenser. The duration of the propelling period is shorter than the duration of either the first withdrawing or the second withdrawing. The propelling of the fluid results in the extension of a small tongue of fluid from the meniscus of the fluid. The second withdrawing of the fluid results in a retraction of the meniscus into the passageway such that only the small tongue of fluid separates and is ejected from the dispenser.

  19. Micro-explosion of compound drops

    NASA Astrophysics Data System (ADS)

    Chen, Chun-Kuei; Lin, Ta-Hui

    2014-08-01

    Introducing water into spray combustion systems, by either water-in-oil emulsification or supplementary water injection, is one of the major techniques for combustion improvement and NOx reduction. Plentiful researches are available on combustion of water-in-oil emulsion fuel drops. The emulsified liquid is a heterogeneous mixture of immiscible liquids. One component forms the continuous phase and the other component forms the discrete phase. The discrete phase consists of globules of the one fluid that are suspended in the continuous phase fluid. Water-in-oil emulsions are commonly considered for combustion applications because emulsions can result in micro-explosion, thereby reducing the average drop diameter to enhance liquid vaporization, and suppressing the formation of soot and NOx. However, the water addition generally does not exceed about 20% for smooth engine operations[!, 21. The combustion characteristics and micro-explosion of emulsion drop were studied by many researchers. The micro-explosion of water in fuel emulsion drops was caused by very fast growth of superheated water vapor bubbles, its superheat limits must be lower than the boiling point temperature of the fuel. These bubbles were primarily governed by the pressure difference between the superheated vapor and the liquid, and by the inertia imparted to the liquid by the motion of the bubble surface[3 6 In this study, we used a coaxial nozzle to generation the multi-component drop. The different type of water-in-oil fuel drops called the compound drops. Unlike an emulsion drop, a compound drop consists of a water core and a fuel shell, which can originate from the phase separation of emulsion[7, 81 or a water drop colliding with a fuel drop[9, 101 Burning and micro-explosion of compound drops have been found to be distinct from those of emulsion drops[9-111 Wang et al.[9 , 101 studied the combustion characteristics of collision merged alkane-water drops. The merged drops appeared in adhesive

  20. Generalized Charts for Determination of Pressure Drop of a High-speed Compressible Fluid in Heat-exchanger Passages I : Air Heated in Smooth Passages of Constant Area with Constant Wall Temperature

    NASA Technical Reports Server (NTRS)

    Valerino, Michael F

    1948-01-01

    In the present paper an analysis is made of the compressible-flow variations occurring in heat-exchanger passages. The results of the analysis describe the flow and heating characteristics for which specific flow passages can be treated as segments of generalized flow systems. The graphical representation of the flow variations in the generalized flow systems can then be utilized as working charts to determine directly the pressure changes occurring in any specific flow passage. On the basis of these results, working charts are constructed to handle the case of air heated at constant wall temperature under turbulent-flow conditions. A method is given of incorporating the effect on the heat-exchanger flow process of high temperature differential between passage wall and fluid as based on recent NACA experimental data. Good agreement is obtained between the experimental and the chart pressure-drop values for passage-wall average temperatures as high as 1752 degrees R (experimental limit) and for flow Mach numbers ranging from 0.32 to 1.00 (choke) at the passage exit.

  1. Eye Drop Tips

    MedlinePlus

    ... Involved News About Us Donate In This Section Eye Drop Tips en Español email Send this article ... the reach of children. Steps For Putting In Eye Drops: Start by tilting your head backward while ...

  2. Attracting Water Drops

    NASA Video Gallery

    Astronauts Cady Coleman and Ron Garan perform the Attracting Water Drops experiment from Chabad Hebrew Academy in San Diego, Calif. This research determines if a free-floating water drop can be att...

  3. Hydrodynamic interactions suppress deformation of suspension drops in Poiseuille flow.

    PubMed

    Sadlej, Krzysztof; Wajnryb, Eligiusz; Ekiel-Jezewska, Maria L

    2010-08-07

    Evolution of a suspension drop entrained by Poiseuille flow is studied numerically at a low Reynolds number. A suspension drop is modeled by a cloud of many nontouching particles, initially randomly distributed inside a spherical volume of a viscous fluid which is identical to the host fluid outside the drop. Evolution of particle positions and velocities is evaluated by the accurate multipole method corrected for lubrication, implemented in the HYDROMULTIPOLE numerical code. Deformation of the drop is shown to be smaller for a larger volume fraction. At high concentrations, hydrodynamic interactions between close particles significantly decrease elongation of the suspension drop along the flow in comparison to the corresponding elongation of the pure-fluid drop. Owing to hydrodynamic interactions, the particles inside a dense-suspension drop tend to stay for a long time together in the central part of the drop; later on, small clusters occasionally separate out from the drop, and are stabilized by quasiperiodic orbits of the constituent nontouching particles. Both effects significantly reduce the drop spreading along the flow. At large volume fractions, suspension drops destabilize by fragmentation, and at low volume fractions, by dispersing into single particles.

  4. Measuring the force of drag on air sheared sessile drops

    NASA Astrophysics Data System (ADS)

    Milne, Andrew J. B.; Fleck, Brian; Amirfazli, Alidad

    2012-11-01

    To blow a drop along or off of a surface (i.e. to shed the drop), the drag force on the drop (based on flow conditions, drop shape, and fluid properties) must overcome the adhesion force between the drop and the surface (based on surface tension, drop shape, and contact angle). While the shedding of sessile drops by shear flow has been studied [Milne, A. J. B. & Amirfazli, A. Langmuir 25, 14155 (2009).], no independent measurements of the drag or adhesion forces have been made. Likewise, analytic predictions are limited to hemispherical drops and low air velocities. We present, therefore, measurements of the drag force on sessile drops at air velocities up to the point of incipient motion. Measurements were made using a modified floating element shear sensor in a laminar low speed wind tunnel to record drag force over the surface with the drop absent, and over the combined system of the surface and drop partially immersed in the boundary layer. Surfaces of different wettabilities were used to study the effects of drop shape and contact angles, with drop volume ranged between approximately 10 and 100 microlitres. The drag force for incipient motion (which by definition equals the maximum of the adhesion force) is compared to simplified models for drop adhesion such as that of Furmidge

  5. Dynamics of a Janus drop in an external flow

    NASA Astrophysics Data System (ADS)

    Shklyaev, S.; Ivantsov, A. O.; Díaz-Maldonado, M.; Córdova-Figueroa, U. M.

    2013-08-01

    The steady motion of a Janus drop under a uniform external flow is considered. First, we analyze the equilibrium shape of a Janus-like drop in a motionless ambient fluid, i.e., the special case of a nearly spherical compound drop with a nearly flat internal interface. This configuration is realizable when the liquids comprising the drop have close interfacial tensions with the ambient fluid, but a small interfacial tension between each other. Then, we consider the flow past a perfect Janus drop composed of two hemispherical domains each occupied by a different fluid. For the sake of simplicity, all the interfaces are assumed nondeformable. The problem is solved both analytically, by means of the Lamb expansion, and numerically. The relation between the flow velocity and the force imposed on the drop, which is a generalization of the classical Hadamard-Rybczynski formula, is found. A torque is also imposed on the drop in the general case. The stable regime of motion of a torque-free drop is found to be axisymmetric, with the less viscous fluid at the upstream face. For this particular configuration, the deformation of the internal interface is also found employing a perturbation technique, whereas the distortion of the drop surface can be safely neglected.

  6. Thermocapillary motion of deformable drops

    NASA Astrophysics Data System (ADS)

    Haj-Hariri, Hossein; Shi, Qingping; Borhan, Ali

    1994-08-01

    The thermocapillary motion of initially spherical drops/bubbles driven by a constant temperature gradient in an unbounded liquid medium is simulated numerically. Effects of convection of momentum and energy, as well as shape deformations, are addressed. The method used is based on interface tracking on a base cartesian grid, and uses a smeared color or indicator function for the determination of the surface topology. Quad-tree adaptive refinement of the cartesian grid is implemented to enhance the fidelity of the surface tracking. It is shown that convection of energy results in a slowing of the drop, as the isotherms get wrapped around the front of the drop. Shape deformation resulting from inertial effects affect the migration velocity. The physical results obtained are in agreement with the existing literature. Furthermore, remarks are made on the sensitivity of the calculated solutions to the smearing of the fluid properties. Analysis and simulations show that the migration velocity depends very strongly on the smearing of the interfacial force whereas it is rather insensitive to the smearing of other properties, hence the adaptive grid.

  7. Dielectrophoresis of a surfactant-laden viscous drop

    NASA Astrophysics Data System (ADS)

    Mandal, Shubhadeep; Bandopadhyay, Aditya; Chakraborty, Suman

    2016-06-01

    The dielectrophoresis of a surfactant-laden viscous drop in the presence of non-uniform DC electric field is investigated analytically and numerically. Considering the presence of bulk-insoluble surfactants at the drop interface, we first perform asymptotic solution for both low and high surface Péclet numbers, where the surface Péclet number signifies the strength of surface convection of surfactants as compared to the diffusion at the drop interface. Neglecting fluid inertia and interfacial charge convection effects, we obtain explicit expression for dielectrophoretic drop velocity for low and high Péclet numbers by assuming small deviation of drop shape from sphericity and small deviation of surfactant concentration from the equilibrium uniform distribution. We then depict a numerical solution, assuming spherical drop, for arbitrary values of Péclet number. Our analyses demonstrate that the asymptotic solution shows excellent agreement with the numerical solution in the limiting conditions of low and high Péclet numbers. The present analysis shows that the flow-induced redistribution of the surfactants at the drop interface generates Marangoni stress, owing to the influence of the surfactant distribution on the local interfacial tension, at the drop interface and significantly alters the drop velocity at steady state. For a perfectly conducting/dielectric drop suspended in perfectly dielectric medium, Marangoni stress always retards the dielectrophoretic velocity of the drop as compared with a surfactant-free drop. For a leaky dielectric drop suspended in another leaky dielectric medium, in the low Péclet number limit, depending on the electrical conductivity and permittivity of both the liquids, the Marangoni stress may aid or retard the dielectrophoretic velocity of the drop. The Marangoni stress also has the ability to move the drop in the opposite direction as compared with a surfactant-free drop. This non-intuitive reverse motion of the drop is

  8. Youth Crime Drop. Report.

    ERIC Educational Resources Information Center

    Butts, Jeffrey A.

    This report examines the recent drop in violent crime in the United States, discussing how much of the decrease seen between 1995-99 is attributable to juveniles (under age 18 years) and older youth (18-24 years). Analysis of current FBI arrest data indicates that not only did America's violent crime drop continue through 1999, but falling youth…

  9. Drop Tower Physics

    ERIC Educational Resources Information Center

    Dittrich, William A.

    2014-01-01

    The drop towers of yesteryear were used to make lead shot for muskets, as described in "The Physics Teacher" in April 2012. However, modern drop towers are essentially elevators designed so that the cable can "break" on demand, creating an environment with microgravity for a short period of time, currently up to nine seconds at…

  10. Axisymmetric Liquid Hanging Drops

    ERIC Educational Resources Information Center

    Meister, Erich C.; Latychevskaia, Tatiana Yu

    2006-01-01

    The geometry of drops hanging on a circular capillary can be determined by numerically solving a dimensionless differential equation that is independent on any material properties, which enables one to follow the change of the height, surface area, and contact angle of drops hanging on a particular capillary. The results show that the application…

  11. Motion of Deformable Drops Through Porous Media

    NASA Astrophysics Data System (ADS)

    Zinchenko, Alexander Z.; Davis, Robert H.

    2017-01-01

    This review describes recent progress in the fundamental understanding of deformable drop motion through porous media with well-defined microstructures, through rigorous first-principles hydrodynamical simulations and experiments. Tight squeezing conditions, when the drops are much larger than the pore throats, are particularly challenging numerically, as the drops nearly coat the porous material skeleton with small surface clearance, requiring very high surface resolution in the algorithms. Small-scale prototype problems for flow-induced drop motion through round capillaries and three-dimensional (3D) constrictions between solid particles, and for gravity-induced squeezing through round orifices and 3D constrictions, show how forcing above critical conditions is needed to overcome trapping. Scaling laws for the squeezing time are suggested. Large-scale multidrop/multiparticle simulations for emulsion flow through a random granular material with multiple drop breakup show that the drop phase generally moves faster than the carrier fluid; both phase velocities equilibrate much faster to the statistical steady state than does the drop-size distribution.

  12. Vibration-induced drop atomization and bursting

    NASA Astrophysics Data System (ADS)

    James, A. J.; Vukasinovic, B.; Smith, Marc K.; Glezer, A.

    2003-02-01

    A liquid drop placed on a vibrating diaphragm will burst into a fine spray of smaller secondary droplets if it is driven at the proper frequency and amplitude. The process begins when capillary waves appear on the free surface of the drop and then grow in amplitude and complexity as the acceleration amplitude of the diaphragm is slowly increased from zero. When the acceleration of the diaphragm rises above a well-defined critical value, small secondary droplets begin to be ejected from the free-surface wave crests. Then, quite suddenly, the entire volume of the drop is ejected from the vibrating diaphragm in the form of a spray. This event is the result of an interaction between the fluid dynamical process of droplet ejection and the vibrational dynamics of the diaphragm. During droplet ejection, the effective mass of the drop diaphragm system decreases and the resonance frequency of the system increases. If the initial forcing frequency is above the resonance frequency of the system, droplet ejection causes the system to move closer to resonance, which in turn causes more vigorous vibration and faster droplet ejection. This ultimately leads to drop bursting. In this paper, the basic phenomenon of vibration-induced drop atomization and drop bursting will be introduced, demonstrated, and characterized. Experimental results and a simple mathematical model of the process will be presented and used to explain the basic physics of the system.

  13. Characterization of biofluids prepared by sessile drop formation.

    PubMed

    Esmonde-White, Karen A; Esmonde-White, Francis W L; Morris, Michael D; Roessler, Blake J

    2014-06-07

    Sessile drop formation, also called drop deposition, has been studied as a potential medical diagnostic, but the effects of complex biofluid rheology on the final deposition pattern are not well understood. We studied two model biofluids, blood plasma and synovial fluid, when deposited onto slightly hydrophilic substrates forming a contact angle of 50-90°. Drops were imaged during the evaporation process and geometric properties of the drop, such as contact angle and drop height, were calculated from the images. The resulting dried biofluid drops were then examined using light microscopy and Raman spectroscopy to assess morphological and chemical composition of the dried drop. The effect of substrate contact angle (surface wetting) and fluid concentration was examined. We found that when biofluids are deposited onto slightly hydrophilic surfaces, with a contact angle of 50-90°, a ring-shaped deposit was formed. Analysis of the drying drop's geometric properties indicates that biofluid dynamics follow the piling model of drop formation, as proposed by Deegan et al. The final deposition pattern varied with substrate surface and concentration, as shown by light microscopy photos of dried drops. The chemical composition of the outer ring was minimally affected by substrate surface, but the spatial heterogeneity of protein distribution within the ring varied with concentration. These results indicate that biofluid drop deposition produces ring-shaped deposits which can be examined by multiple analytical techniques.

  14. Sliding viscoelastic drops on slippery surfaces

    NASA Astrophysics Data System (ADS)

    Xu, H.; Clarke, A.; Rothstein, J. P.; Poole, R. J.

    2016-06-01

    We study the sliding of drops of constant-viscosity dilute elastic liquids (Boger fluids) on various surfaces caused by sudden surface inclination. For smooth or roughened hydrophilic surfaces, such as glass or acrylic, there is essentially no difference between these elastic liquids and a Newtonian comparator fluid (with identical shear viscosity, surface tension, and static contact angle). In contrast for embossed polytetrafluoroethylene superhydrophobic surfaces, profound differences are observed: the elastic drops slide at a significantly reduced rate and complex branch-like patterns are left on the surface by the drop's wake including, on various scales, beads-on-a-string like phenomena. Microscopy images indicate that the strong viscoelastic effect is caused by stretching filaments of fluid from isolated islands, residing at pinning sites on the surface pillars, of the order ˜30 μm in size. On this scale, the local strain rates are sufficient to extend the polymer chains, locally increasing the extensional viscosity of the solution, retarding the drop and leaving behind striking branch-like structures on much larger scales.

  15. The Vibration of an Inviscid Incompressible Sessile Drop

    NASA Astrophysics Data System (ADS)

    Smith, Marc

    2009-11-01

    The fundamental frequencies and normal modes of vibration of a sessile drop supported on a horizontal planar surface are found using an integrated analytical and numerical technique. Spherical coordinates are used to describe the interface shape, but the potential flow field inside the drop is computed numerically using the finite element method. The numerical velocity potentials at the interface for both the fluid inside the drop and outside are fitted using a Legendre series. When these series are combined in the interfacial normal-stress balance the result is a linear eigenvalue problem that is solved numerically. Results will be presented for sessile drops with different contact angles without gravity and compared to experimental data. This technique can also be extended to sessile drops with gravity, in which the drop shape is flattened, and to substrate geometries that are not planar, such as a drop in a shallow cavity or hole.

  16. Destabilising Pickering emulsions by drop flocculation and adhesion.

    PubMed

    Whitby, Catherine P; Khairul Anwar, Hunainah; Hughes, James

    2016-03-01

    We have investigated how emulsions of water drops coated by organoclay particles destabilise in organic solvents. The drops destabilise and the emulsions undergo a fluid-solid transition if the particles are poorly wetted by the solvent. We show that the drops adhere together and form three-dimensional networks as the fraction of the poor-quality solvent in the mixture increases. Microscopic observations revealed that the drops coalesce into buckled, non-spherical shapes in mixtures rich in poor-quality solvent. A key finding is that destabilisation is favoured under conditions where the energy of adhesion between the particle layers coating drops is comparable to the energy required to detach the particles from the drops. Rupture of the interfacial layer produces particle flocs and uncoated, unstable water drops that settle out of the emulsion.

  17. Characterization of Biofluids Prepared by Sessile Drop Formation

    PubMed Central

    Esmonde-White, Karen A.; Esmonde-White, Francis W.L.; Morris, Michael D.; Roessler, Blake J.

    2014-01-01

    Sessile drop formation, also called drop deposition, has been studied as a potential medical diagnostic, but the effects of complex biofluid rheology on the final deposition pattern are not well understood. We studied two model biofluids, blood plasma and synovial fluid, when deposited onto slightly hydrophilic substrates forming a contact angle of 50–90°. Drops were imaged during the evaporation process and geometric properties of the drop, such as contact angle and drop height, were calculated from the images. The resulting dried biofluid drops were then examined using light microscopy and Raman spectroscopy to assess morphological and chemical composition of the dried drop. The effect of substrate contact angle (surface wetting) and fluid concentration was examined. We found that when biofluids are deposited onto slightly hydrophilic surfaces, with a contact angle of 50–90°, a ring-shaped deposit was formed. Analysis of the drying drop’s geometric properties indicates that biofluid dynamics follow the piling model of drop formation, as proposed by Deegan et al. The final deposition pattern varied with substrate surface and concentration, as shown by light microscopy photos of dried drops. The chemical composition of the outer ring was minimally affected by substrate surface, but the spatial heterogeneity of protein distribution within the ring varied with concentration. These results indicate that biofluid drop deposition produces ring-shaped deposits which can be examined by multiple analytical techniques. PMID:24757707

  18. Drop Tower Workshop

    NASA Technical Reports Server (NTRS)

    Urban, David

    2013-01-01

    Ground based microgravity facilities are an important proving ground for space experiments, ground-based research and space hardware risk mitigation. An overview of existing platforms will be discussed with an emphasis on drop tower capabilities. The potential for extension to partial gravity conditions will be discussed. Input will be solicited from attendees for their potential to use drop towers in the future and the need for enhanced capabilities (e.g. partial gravity)

  19. Rain Drop Charge Sensor

    NASA Astrophysics Data System (ADS)

    S, Sreekanth T.

    begin{center} Large Large Rain Drop Charge Sensor Sreekanth T S*, Suby Symon*, G. Mohan Kumar (1) , S. Murali Das (2) *Atmospheric Sciences Division, Centre for Earth Science Studies, Thiruvananthapuram 695011 (1) D-330, Swathi Nagar, West Fort, Thiruvananthapuram 695023 (2) Kavyam, Manacaud, Thiruvananthapuram 695009 begin{center} ABSTRACT To study the inter-relations with precipitation electricity and precipitation microphysical parameters a rain drop charge sensor was designed and developed at CESS Electronics & Instrumentation Laboratory. Simultaneous measurement of electric charge and fall speed of rain drops could be done using this charge sensor. A cylindrical metal tube (sensor tube) of 30 cm length is placed inside another thick metal cover opened at top and bottom for electromagnetic shielding. Mouth of the sensor tube is exposed and bottom part is covered with metal net in the shielding cover. The instrument is designed in such a way that rain drops can pass only through unhindered inside the sensor tube. When electrically charged rain drops pass through the sensor tube, it is charged to the same magnitude of drop charge but with opposite polarity. The sensor tube is electrically connected the inverted input of a current to voltage converter operational amplifier using op-amp AD549. Since the sensor is electrically connected to the virtual ground of the op-amp, the charge flows to the ground and the generated current is converted to amplified voltage. This output voltage is recorded using a high frequency (1kHz) voltage recorder. From the recorded pulse, charge magnitude, polarity and fall speed of rain drop are calculated. From the fall speed drop diameter also can be calculated. The prototype is now under test running at CESS campus. As the magnitude of charge in rain drops is an indication of accumulated charge in clouds in lightning, this instrument has potential application in the field of risk and disaster management. By knowing the charge

  20. Nanofluid Drop Evaporation: Experiment, Theory, and Modeling

    NASA Astrophysics Data System (ADS)

    Gerken, William James

    Nanofluids, stable colloidal suspensions of nanoparticles in a base fluid, have potential applications in the heat transfer, combustion and propulsion, manufacturing, and medical fields. Experiments were conducted to determine the evaporation rate of room temperature, millimeter-sized pendant drops of ethanol laden with varying amounts (0-3% by weight) of 40-60 nm aluminum nanoparticles (nAl). Time-resolved high-resolution drop images were collected for the determination of early-time evaporation rate (D2/D 02 > 0.75), shown to exhibit D-square law behavior, and surface tension. Results show an asymptotic decrease in pendant drop evaporation rate with increasing nAl loading. The evaporation rate decreases by approximately 15% at around 1% to 3% nAl loading relative to the evaporation rate of pure ethanol. Surface tension was observed to be unaffected by nAl loading up to 3% by weight. A model was developed to describe the evaporation of the nanofluid pendant drops based on D-square law analysis for the gas domain and a description of the reduction in liquid fraction available for evaporation due to nanoparticle agglomerate packing near the evaporating drop surface. Model predictions are in relatively good agreement with experiment, within a few percent of measured nanofluid pendant drop evaporation rate. The evaporation of pinned nanofluid sessile drops was also considered via modeling. It was found that the same mechanism for nanofluid evaporation rate reduction used to explain pendant drops could be used for sessile drops. That mechanism is a reduction in evaporation rate due to a reduction in available ethanol for evaporation at the drop surface caused by the packing of nanoparticle agglomerates near the drop surface. Comparisons of the present modeling predictions with sessile drop evaporation rate measurements reported for nAl/ethanol nanofluids by Sefiane and Bennacer [11] are in fairly good agreement. Portions of this abstract previously appeared as: W. J

  1. Surface and Bulk Oscillations of Sessile Drops: Clearing Up Confusion and Understanding Wind Sheared Drops

    NASA Astrophysics Data System (ADS)

    Milne, Andrew J. B.; Defez Garcia, Beatriz; Cabrerizo Vilchez, Miguel; Amirfazli, Alidad

    2011-11-01

    Sessile drop oscillations are studied in the presence of a shearing airflow, and varying body force. The various possibilities for analysis, (center of mass or drop surface oscillations) are elucidated through presenting a unifying analysis framework based on wavenumber, frequency, and fluid properties. This work examines a range of fluid properties in a single study for the first time. A dispersion relation is found relating the frequency of centroid oscillation and capillary-gravity wave number, depending on the ratio (surface tension/liquid density)1/2, drop size- 3 / 2 and contact angle. The effects of contact angle are more complex than previously suggested simplifications, or analytic solutions for axisymetric drops and must at present be treated empirically. The growth of sessile drop oscillations is linear at low air velocities and exponential at higher air velocities. This is explained by drawing analogies to drops experiencing a varying body force, and to wind driven capillary-gravity waves on lakes, respectively. Liquid viscosity retards the growth of the waves, and has other important effects.

  2. Magnetically focused liquid drop radiator

    DOEpatents

    Botts, Thomas E.; Powell, James R.; Lenard, Roger

    1986-01-01

    A magnetically focused liquid drop radiator for application in rejecting rgy from a spacecraft, characterized by a magnetizable liquid or slurry disposed in operative relationship within the liquid droplet generator and its fluid delivery system, in combination with magnetic means disposed in operative relationship around a liquid droplet collector of the LDR. The magnetic means are effective to focus streams of droplets directed from the generator toward the collector, thereby to assure that essentially all of the droplets are directed into the collector, even though some of the streams may be misdirected as they leave the generator. The magnetic focusing means is also effective to suppress splashing of liquid when the droplets impinge on the collector.

  3. Magnetically focused liquid drop radiator

    DOEpatents

    Botts, T.E.; Powell, J.R.; Lenard, R.

    1984-12-10

    A magnetically focused liquid drop radiator for application in rejecting energy from a spacecraft, characterized by a magnetizable liquid or slurry disposed in operative relationship within the liquid droplet generator and its fluid delivery system, in combination with magnetic means disposed in operative relationship around a liquid droplet collector of the LDR. The magnetic means are effective to focus streams of droplets directed from the generator toward the collector, thereby to assure that essentially all of the droplets are directed into the collector, even though some of the streams may be misdirected as they leave the generator. The magnetic focusing means is also effective to suppress splashing of liquid when the droplets impinge on the collector.

  4. On the Stability of Rotating Drops

    PubMed Central

    Nurse, A. K.; Coriell, S. R.; McFadden, G. B.

    2015-01-01

    We consider the equilibrium and stability of rotating axisymmetric fluid drops by appealing to a variational principle that characterizes the equilibria as stationary states of a functional containing surface energy and rotational energy contributions, augmented by a volume constraint. The linear stability of a drop is determined by solving the eigenvalue problem associated with the second variation of the energy functional. We compute equilibria corresponding to both oblate and prolate shapes, as well as toroidal shapes, and track their evolution with rotation rate. The stability results are obtained for two cases: (i) a prescribed rotational rate of the system (“driven drops”), or (ii) a prescribed angular momentum (“isolated drops”). For families of axisymmetric drops instabilities may occur for either axisymmetric or non-axisymmetric perturbations; the latter correspond to bifurcation points where non-axisymmetric shapes are possible. We employ an angle-arc length formulation of the problem which allows the computation of equilibrium shapes that are not single-valued in spherical coordinates. We are able to illustrate the transition from spheroidal drops with a strong indentation on the rotation axis to toroidal drops that do not extend to the rotation axis. Toroidal drops with a large aspect ratio (major radius to minor radius) are subject to azimuthal instabilities with higher mode numbers that are analogous to the Rayleigh instability of a cylindrical interface. Prolate spheroidal shapes occur if a drop of lower density rotates within a denser medium; these drops appear to be linearly stable. This work is motivated by recent investigations of toroidal tissue clusters that are observed to climb conical obstacles after self-assembly [Nurse et al., Journal of Applied Mechanics 79 (2012) 051013]. PMID:26958440

  5. Numerical investigation of phase relationships in an oscillating sessile drop

    NASA Astrophysics Data System (ADS)

    Korenchenko, A. E.; Malkova, J. P.

    2015-10-01

    Forced linear oscillations of a viscous drop placed on a horizontal surface vibrating in perpendicular direction are investigated. The problem is solved for two cases: (1) constant contact angle, and (2) pinned contact line. Phase-frequency and amplitude-frequency characteristics of oscillations of the drop apex are found for the first axisymmetrical mode of oscillations. The independence of the difference of oscillation phases of the drop apex and the substrate on fluid density, viscosity, surface tension, and drop size as well as on presence or absence of the gravity force was demonstrated.

  6. Simple analytical model of capillary flow in an evaporating sessile drop.

    PubMed

    Tarasevich, Yuri Yu

    2005-02-01

    An analytical expression of hydrodynamic potential inside an evaporating sessile drop with pinned contact line is found. The problem is considered for a hemispherical drop (with the contact angle of 90 degrees ) at the very early stages of the evaporation process when the shape of the drop is still a hemisphere and the evaporation field is uniform. The capillary flow carries a fluid from the drop apex to the contact line. Comparison with the published calculations performed using lubrication approximation (very thin drop) suggests that qualitative picture of the capillary flow is insensitive to the ratio of initial drop height to the drop radius.

  7. Complex Drop Impact Morphology.

    PubMed

    Grishaev, Viktor; Iorio, Carlo Saverio; Dubois, Frank; Amirfazli, A

    2015-09-15

    The aim of this work is to understand the changes in the observed phenomena during particle-laden drop impact. The impact of millimeter-size drops was investigated onto hydrophilic (glass) and hydrophobic (polycarbonate) substrates. The drops were dispersions of water and spherical and nearly iso-dense hydrophobic particles with diameters of 200 and 500 μm. The impact was studied by side and bottom view images in the range 150 ≤ We ≤ 750 and 7100 ≤ Re ≤ 16400. The particles suppressed the appearance of singular jetting and drop partial rebound but promoted splashing, receding breakup, and rupture. The drops with 200 μm particles spread in two phases: fast and slow, caused by inertial and capillary forces, respectively. Also, the increase in volume fraction of 200 μm particle led to a linear decrease in the maximum spreading factor caused by the inertia force on both hydrophilic and hydrophobic substrates. The explanation of this reduction was argued to be the result of energy dissipation through frictional losses between particles and the substrate.

  8. Hydrodynamic interaction of two deformable drops in confined shear flow

    NASA Astrophysics Data System (ADS)

    Chen, Yongping; Wang, Chengyao

    2014-09-01

    We investigate hydrodynamic interaction between two neutrally buoyant circular drops in a confined shear flow based on a computational fluid dynamics simulation using the volume-of-fluid method. The rheological behaviors of interactive drops and the flow regimes are explored with a focus on elucidation of underlying physical mechanisms. We find that two types of drop behaviors during interaction occur, including passing-over motion and reversing motion, which are governed by the competition between the drag of passing flow and the entrainment of reversing flow in matrix fluid. With the increasing confinement, the drop behavior transits from the passing-over motion to reversing motion, because the entrainment of the reversing-flow matrix fluid turns to play the dominant role. The drag of the ambient passing flow is increased by enlarging the initial lateral separation due to the departure of the drop from the reversing flow in matrix fluid, resulting in the emergence of passing-over motion. In particular, a corresponding phase diagram is plotted to quantitatively illustrate the dependence of drop morphologies during interaction on confinement and initial lateral separation.

  9. Ultrasonic characterization of single drops of liquids

    DOEpatents

    Sinha, Dipen N.

    1998-01-01

    Ultrasonic characterization of single drops of liquids. The present invention includes the use of two closely spaced transducers, or one transducer and a closely spaced reflector plate, to form an interferometer suitable for ultrasonic characterization of droplet-size and smaller samples without the need for a container. The droplet is held between the interferometer elements, whose distance apart may be adjusted, by surface tension. The surfaces of the interferometer elements may be readily cleansed by a stream of solvent followed by purified air when it is desired to change samples. A single drop of liquid is sufficient for high-quality measurement. Examples of samples which may be investigated using the apparatus and method of the present invention include biological specimens (tear drops; blood and other body fluid samples; samples from tumors, tissues, and organs; secretions from tissues and organs; snake and bee venom, etc.) for diagnostic evaluation, samples in forensic investigations, and detection of drugs in small quantities.

  10. Bursting drops in solid dielectrics caused by high voltages.

    PubMed

    Wang, Qiming; Suo, Zhigang; Zhao, Xuanhe

    2012-01-01

    Fluid drops tend to be spheres--a shape that minimizes surface energy. In thunderstorm clouds, drops can become unstable and emit thin jets when charged beyond certain limits. The instability of electrified drops in gases and liquids has been widely studied and used in applications including ink-jet printing, electrospinning nanofibers, microfluidics and electrospray ionization. Here we report a different scenario: drops in solids become unstable and burst under sufficiently high electric fields. We find the instability of drops in solids morphologically resembles that in liquids, but the critical electric field for the instability follows a different scaling due to elasticity of solids. Our observations and theoretical models not only advance the fundamental understanding of electrified drops, but also suggest a new failure mechanism of high energy density dielectric polymers, which have diverse applications ranging from capacitors for power grids and electric vehicles to muscle-like transducers for soft robots and energy harvesting.

  11. Bursting Drops in Solid Dielectrics Caused by High Voltages

    PubMed Central

    Wang, Qiming; Suo, Zhigang

    2013-01-01

    Drops in fluids tend to be spheres—a shape that minimizes surface energy. In thunderstorm clouds, drops can become unstable and emit thin jets when charged beyond certain limits. The instability of electrified drops in gases and liquids has been widely studied and used in applications including ink-jet printing, electrospinning nano-fibers, microfluidics and electrospray ionization. Here we report a different scenario: drops in solids become unstable and burst under sufficiently high electric fields. We find the instability of drops in solids morphologically resembles that in liquids, but the critical electric field for the instability follows a different scaling due to elasticity of solids. Our observations and theoretical models not only advance the fundamental understanding of electrified drops but also suggest a new failure mechanism of high-energy-density dielectric polymers, which have diverse applications ranging from capacitors for power grids and electric vehicles to muscle-like transducers for soft robots and energy harvesting. PMID:23093194

  12. Effect of Conformation and Drop Properties on Surface-Enhanced Raman Spectroscopy of Dried Biopolymer Drops

    PubMed Central

    Esmonde-White, Karen A.; Le Clair, Stephanie V.; Roessler, Blake J.; Morris, Michael D.

    2011-01-01

    Biofluids are complex solutions consisting of small ions and large biopolymers such as DNA, proteins or proteoglycans. Biopolymers affect fluid properties but their effect on drop deposition has not been examined. Hyaluronic acid (HA), an important component in synovial fluid, was chosen as a model biopolymer, and examined using surface-enhanced Raman spectroscopy (SERS). Nanoliter volumes of HA solutions were dried onto a patterned SERS substrate and spectra were collected from the dried hyaluronic acid drops with a near-infrared Raman microscope. Characteristic hyaluronic acid bands were examined. Capillary viscometry measured properties of HA solutions and entanglement behavior was also modeled using scaling theory principles. Viscosity measurements were incorporated into models of suspended particle droplets to account for the effect of inter-chain attraction on droplet formation. Microscope images were used to evaluate shape of the dried drop. Relative drop thickness was estimated from concentric rings found at drop edges using established models of light interference by thin films. We found SERS spectra were sensitive not only to polymer conformation, but also to type of deposition (ring versus uniform), and the thickness of the resulting deposition. These data suggest an approach to elucidate the effects of biopolymers and dehydrated biofluids on SERS analysis. PMID:18498691

  13. The Vibration of an Inviscid Incompressible Sessile Drop

    NASA Astrophysics Data System (ADS)

    Smith, Marc K.

    2008-11-01

    The fundamental frequencies and modes of vibration of a free spherical drop of inviscid incompressible fluid were computed 129 years ago by Lord Rayleigh. The analysis was possible because of simplifications resulting from the use of spherical coordinates. These same simplifications don't occur for a sessile drop, i.e., when the drop is supported on a horizontal planar surface, except for the case of a hemispherical drop. The present work describes an integrated analytical and numerical technique for the computation of the fundamental frequencies and modes of vibration of a supported sessile drop. Spherical coordinates are used to describe the interface shape, but the flow field inside the drop is computed numerically using the finite element method. Combining these techniques produces a linear eigenvalue problem that is solved numerically. Results will be presented for sessile drops with different contact angles without gravity and compared to experimental data. This technique can also be extended to sessile drops with gravity, in which the drop shape is flattened, and to substrate geometries that are not planar, such as a drop in a shallow cavity or hole.

  14. WITHDRAWN: Axisymmetric Adaptive Drop/Interface Impacting Study

    NASA Astrophysics Data System (ADS)

    Zheng, Xiaoming; Lowengrub, John; Cristini, Vittorio

    2005-11-01

    The impact of a drop upon an interface is studied using an axisymmetric adaptive level-set/finite element method. Under certain conditions, the drop will rebound off the interface before breaking through. The drop fluid and the fluid below the interface are identical. We characterize the behavior in terms of the relevant nondimensional parameters: the Reynolds number, the Weber number, and the viscosity and density ratios of the fluid components. One of the primary difficulties in performing numerical simulations of such flows is the accurate resolution of the lubrication forces that arise in the near contact region between the drop and interface. To overcome this difficulty, we use a spatially and temporally adaptive mesh together with a new, stable and accurate projection method for the Navier-Stokes equations and a mass-conserving level-set algorithm for capturing the motion of the drop and interface (J. Comp. Phys., v. 208, 2005). We validate our algorithm by successfully matching the recent experimental results on drop/interface impact by Mohamed-Kassim and Longmire (Phys. Fluids, v. 15, 2003).

  15. Drop interaction with solid boundaries in liquid/liquid systems

    NASA Astrophysics Data System (ADS)

    Bordoloi, Ankur Deep

    The present experimental work was motivated primarily by the CO 2 sequestration process. In a possible scenario during this process, gravity driven CO2 bubbles coalesce at an interface near the rock surface. In another scenario, trapped CO2 fluid may escape from a porous matrix overcoming interfacial force inside a pore. Based on these potential scenarios, the current research was divided into two broad experimental studies. In the first part, coalescence at a quiescent interface of two analogous fluids (silicone oil and water/glycerin mixture) was investigated for water/glycerin drops with Bond number (Bo) ~7 and Ohnesorge number ~ 0.01 using high-speed imaging and time-resolved tomographic PIV. Two perturbation cases with a solid particle wetted in oil and water/glycerin placed adjacent to the coalescing drop were considered. The results were compared with coalescence of a single drop and that of a drop neighBored by a second drop of equivalent size. Each perturbing object caused an initial tilting of the drop, influencing its rupture location, subsequent film retraction and eventual collapse behavior. Once tilted, drops typically ruptured near their lowest vertical position which was located either toward or away from the perturbing object depending on the case. The trends in local retraction speed of the ruptured film and the overall dynamics of the collapsing drops were discussed in detail. In the second part, the motion of gravity driven drops (B o~0.8-11) through a confining orifice d/D<1) was studied using high speed imaging and planar PIV. Drops of water/glycerin, surrounded by silicone oil, fall toward and encounter the orifice plate after reaching terminal speed. The effects of surface wettability were investigated for Both round-edged and sharp-edged orifices. For the round-edged case, a thin film of surrounding oil prevented the drop fluid from contacting the orifice surface, such that the flow outcomes of the drops were independent of surface

  16. Fluid Flow Experiment for Undergraduate Laboratory.

    ERIC Educational Resources Information Center

    Vilimpochapornkul, Viroj; Obot, Nsima T.

    1986-01-01

    The undergraduate fluid mechanics laboratory at Clarkson University consists of three experiments: mixing; drag measurements; and fluid flow and pressure drop measurements. The latter experiment is described, considering equipment needed, procedures used, and typical results obtained. (JN)

  17. Drop tube technical tasks

    NASA Technical Reports Server (NTRS)

    Workman, G. L.

    1986-01-01

    Criteria, using fundamental thermochemical dynamics, were developed to assist a scientist using the Drop Tube Facility in designing a good experiment. The types of parameters involved in designing the experiments include the type of furnace, the type of atmosphere, and in general which materials are better behaved than others as determined by past experience in the facility. One of the major advantages of the facility lies in its ability to provide large undercoolings in the cooling curve during the drops. A beginning was to consider the effect of oxygen and other gases upon the amount of undercooling observed. The starting point of the thermochemistry was given by Ellingham and later transformed into what is known as the Richardson Chart. The effect of surface oxidations upon the nucleation phenomena can be observed in each specimen.

  18. Electrostatic drops in orbit

    NASA Astrophysics Data System (ADS)

    Rodriguez, Isabel J.; Schmidt, Erin; Weislogel, Mark M.; Pettit, Donald

    2016-11-01

    We present what we think are the first intentional electrostatic orbits in the near-weightless environment of a drop tower. Classical physics problems involving Coulombic forces in orbital mechanics have traditionally been confined to thought experiments due to practical terrestrial experimental limitations, namely, the preponderance of gravity. However, the use of a drop tower as an experimental platform can overcome this challenge for brief periods. We demonstrate methanol-water droplets in orbit around a variety of charged objects- some of which can be used to validate special cases of N-body systems. Footage collected via a high-speed camera is analyzed and orbital trajectories are compared with existing theoretical predictions. Droplets of diameters 0.5 to 2mm in a variety of obits are observed. Due to the repeatability of drop tower initial conditions and effective low-g environment, such experiments may be used to construct empirical analogues and confirm analyses toward the benefit of other fields including space and planetary science. NASA Cooperative Agreement NNX12A047A, Portland State LSAMP, Robert E. McNair Scholars Program.

  19. Resonances, radiation pressure and optical scattering phenomena of drops and bubbles

    NASA Technical Reports Server (NTRS)

    Marston, P. L.; Goosby, S. G.; Langley, D. S.; Loporto-Arione, S. E.

    1982-01-01

    Acoustic levitation and the response of fluid spheres to spherical harmonic projections of the radiation pressure are described. Simplified discussions of the projections are given. A relationship between the tangential radiation stress and the Konstantinov effect is introduced and fundamental streaming patterns for drops are predicted. Experiments on the forced shape oscillation of drops are described and photographs of drop fission are displayed. Photographs of critical angle and glory scattering by bubbles and rainbow scattering by drops are displayed.

  20. The Drop Tower Bremen -Experiment Operation

    NASA Astrophysics Data System (ADS)

    Könemann, Thorben; von Kampen, Peter; Rath, Hans J.

    The idea behind the drop tower facility of the Center of Applied Space Technology and Micro-gravity (ZARM) in Bremen is to provide an inimitable technical opportunity of a daily access to short-term weightlessness on earth. In this way ZARM`s european unique ground-based microgravity laboratory displays an excellent economic alternative for research in space-related conditions at low costs comparable to orbital platforms. Many national and international ex-perimentalists motivated by these prospects decide to benefit from the high-quality and easy accessible microgravity environment only provided by the Drop Tower Bremen. Corresponding experiments in reduced gravity could open new perspectives of investigation methods and give scientists an impressive potential for a future technology and multidisciplinary applications on different research fields like Fundamental Physics, Astrophysics, Fluid Dynamics, Combus-tion, Material Science, Chemistry and Biology. Generally, realizing microgravity experiments at ZARM`s drop tower facility meet new requirements of the experimental hardware and may lead to some technical constraints in the setups. In any case the ZARM Drop Tower Operation and Service Company (ZARM FAB mbH) maintaining the drop tower facility is prepared to as-sist experimentalists by offering own air-conditioned laboratories, clean rooms, workshops and consulting engineers, as well as scientific personal. Furthermore, ZARM`s on-site apartment can be used for accommodations during the experiment campaigns. In terms of approaching drop tower experimenting, consulting of experimentalists is mandatory to successfully accomplish the pursued drop or catapult capsule experiment. For this purpose there will be a lot of expertise and help given by ZARM FAB mbH in strong cooperation to-gether with the experimentalists. However, in comparison to standard laboratory setups the drop or catapult capsule setup seems to be completely different at first view. While defining a

  1. Leidenfrost Drop on a Step

    NASA Astrophysics Data System (ADS)

    Lagubeau, Guillaume; Le Merrer, Marie; Clanet, Christophe; Quere, David

    2008-11-01

    When deposited on a hot plate, a water droplet evaporates quickly. However, a vapor film appears under the drop above a critical temperature, called Leidenfrost temperature, which insulates the drop from its substrate. Linke & al (2006) reported a spontaneous movement of such a drop, when deposited on a ratchet. We study here the case of a flat substrate decorated with a single micrometric step. The drop is deposited on the lower part of the plate and pushed towards the step at small constant velocity. If the kinetic energy of the drop is sufficient, it can climb up the step. In that case, depending on the substrate temperature, the drop can either be decelerated or accelerated by the step. We try to understand the dynamics of these drops, especially the regime where they accelerate. Taking advantage of this phenomenon, we could then build a multiple-step setup, making it possible for a Leidenfrost drop to climb stairs.

  2. Formation and Combustion of Unconfined Drop Clusters in Microgravity

    NASA Technical Reports Server (NTRS)

    Liu, S.; Craig, G.; Zhang, Y.; Ruff, G. A.

    1997-01-01

    Single-drop and droplet array studies have become common methods to isolate and investigate the effects of any of the complexities that enter into the drop combustion process. Microgravity environments are required to allow larger drops to be studied while minimizing or eliminating the confounding effects of buoyancy. Based on the results from current isolated drop, drop array, and spray studies funded through the Microgravity Science and Applications Division, it has become clear that even with the effects of buoyancy removed, the extrapolation of results from droplet array studies to spray flames is difficult. The problem occurs because even the simplest spray systems introduce complexities of multi-disperse drop sizes and drop-drop interactions, coupled with more complicated fluid dynamics. Not only do these features make the interpretation of experimental data difficult, they also make the problem very difficult to analyze computationally. Group combustion models, in which the interaction between droplets is treated on a statistical manner, have become a popular method to investigate the behavior of large numbers of interacting droplets, particularly through the work of Ryan et al. and Bellan and co-workers. While these models idealize the actual spray systems to a point where they can be treated computationally, the experimental analogy to these models is difficult to achieve because it requires the formation and Combustion of drop clusters without the effects of buoyancy. Therefore, even though these models have provided useful and insightful information, the verification of the results by direct comparison with experimental data is still lacking.

  3. Drops subjected to surface acoustic waves: flow dynamics

    NASA Astrophysics Data System (ADS)

    Brunet, Philippe; Baudoin, Michael; Bou Matar, Olivier; Dynamique Des Systèmes Hors Equilibre Team; Aiman-Films Team

    2012-11-01

    Ultrasonic acoustic waves of frequency beyond the MHz are known to induce streaming flow in fluids that can be suitable to perform elementary operations in microfluidics systems. One of the currently appealing geometry is that of a sessile drop subjected to surface acoustic waves (SAW). Such Rayleigh waves produce non-trival actuation in the drop leading to internal flow, drop displacement, free-surface oscillations and atomization. We recently carried out experiments and numerical simulations that allowed to better understand the underlying physical mechanisms that couple acoustic propagation and fluid actuation. We varied the frequency and amplitude of actuation, as well as the properties of the fluid, and we measured the effects of these parameters on the dynamics of the flow. We compared these results to finite-elements numerical simulations.

  4. An evaporation model of multicomponent solution drops

    NASA Astrophysics Data System (ADS)

    Sartori, Silvana; Liñán, Amable; Lasheras, Juan C.

    2010-11-01

    Solutions of polymers are widely used in the pharmaceutical industry as tablets coatings. These allow controlling the rate at which the drug is delivered, taste or appearance. The coating is performed by spraying and drying the tablets at moderate temperatures. The wetting of the coating solution on the pill's surface depends on the droplet Webber and Re numbers, angle of impact and on the rheological properties of the droplet. We present a model for the evaporation of multicomponent solutions droplets in a hot air environment with temperatures substantially lower than the boiling temperature of the solvent. As the liquid vaporizes from the surface the fluid in the drop increases in concentration, until reaching its saturation point. After saturation, precipitation occurs uniformly within the drop. As the surface regresses, a compacting front formed by the precipitate at its maximum packing density advances into the drop, while the solute continues precipitating uniformly. This porous shell grows fast due to the double effect of surface regression and precipitation. The evaporation rate is determined by the rates at which heat is transported to the droplet surface and at which liquid vapor diffuses away from it. When the drop is fully compacted, the evaporation is drastically reduced.

  5. The migration of a compound drop due to thermocapillarity

    NASA Technical Reports Server (NTRS)

    Morton, David S.; Subramanian, R. Shankar; Balasubramaniam, R.

    1990-01-01

    The quasistatic thermocapillary motion of a compound drop in an unbounded fluid possessing a uniform temperature gradient is analyzed. For completeness, gravitational effects are included in the treatment. The general model is formulated, and the equations for the concentric case are solved using spherical polar coordinates, while the eccentric case is handled using bispherical coordinates. Results are given for the velocity of the drop as well as that of the droplet with respect to the drop, along with useful approximations. Illustrative results are presented graphically for the thermocapillary migration of a compound drop in the special case when the droplet is a gas bubble. In addition to the velocities of the drop and the bubble, representative isotherms and streamlines also are presented which display interesting qualitative features.

  6. Symmetry breaking in drop bouncing on curved surfaces

    PubMed Central

    Liu, Yahua; Andrew, Matthew; Li, Jing; Yeomans, Julia M.; Wang, Zuankai

    2015-01-01

    The impact of liquid drops on solid surfaces is ubiquitous in nature, and of practical importance in many industrial processes. A drop hitting a flat surface retains a circular symmetry throughout the impact process. Here we show that a drop impinging on Echevaria leaves exhibits asymmetric bouncing dynamics with distinct spreading and retraction along two perpendicular directions. This is a direct consequence of the cylindrical leaves that have a convex/concave architecture of size comparable to the drop. Systematic experimental investigations on mimetic surfaces and lattice Boltzmann simulations reveal that this novel phenomenon results from an asymmetric momentum and mass distribution that allows for preferential fluid pumping around the drop rim. The asymmetry of the bouncing leads to ∼40% reduction in contact time. PMID:26602170

  7. Deformation and stability of surfactant - or particle - laden drop

    NASA Astrophysics Data System (ADS)

    Brosseau, Quentin; Pradillo, Gerardo; Oberlander, Andrew; Vlahovska, Petia; SoftMech@Brown Team

    2015-11-01

    We present an experimental study of the behavior of a drop covered with insoluble surfactant or colloidal particles in a uniform DC electric field. Steady drop shapes, drop evolution upon application of the field, and drop relaxation after the field is turned off are observed for leaky dielectric fluids: Polybutadiene (PB), Silicon oil (PDMS), and Castor oil (CO). The surfactant is generated at the drop interface by reaction between end-functionalized PB and PDMS. The experimental data is compared with existing theoretical models for the steady shape of surfactant covered droplet, and adjusted models taking into account the presence of colloidal spheres with range of electrical properties. We will discuss the complex interplay of shape deformation, surfactant elasticity, particle redistribution, and interfacial charging in droplet electrohydrodynamics. Our results are important for understanding electrorheology of emulsions commonly found in the petroleum industry. We acknowledge grant NSF CBET 1437545 for funding.

  8. Drop foot corrective device

    NASA Technical Reports Server (NTRS)

    Deis, B. C. (Inventor)

    1986-01-01

    A light weight, economical device to alleviate a plurality of difficulties encountered in walking by a victim suffering from a drop foot condition is discussed. A legband girdles the leg below the knee and above the calf providing an anchor point for the upper end of a ligament having its lower end attached to a toe of a shoe or a toe on the foot. The ligament is of such length that the foot is supported thereby and retained in a normal position during walking.

  9. Coffee Stains from Drops with Receding Contact Lines

    NASA Astrophysics Data System (ADS)

    Freed-Brown, Julian

    2015-03-01

    We present a framework for calculating the surface density profile of a coffee stain deposited by a drying drop with a receding contact line. For standard coffee stains, the fluid pins to the substrate, forces flow towards the exterior of the drop and deposits a thin, concentrated ring of particles. Unlike a pinned drop, a receding drop pushes fluid towards its interior and continuously deposits mass across its substrate as it evaporates. This gives rise to a new class of mountain-like morphologies that are not seen in the standard coffee ring effect but are reminiscent of recent experimental results. For a thin, circular drop with uniform evaporation, we calculate the surface density profile analytically and find that it diverges towards the center of the drop as η ~r - 1 / 2 , where r is the distance from the center. We estimate how this divergence is softened due to solute interactions at the final stage of drying. Our framework can easily be extended numerically or analytically to investigate novel stain morphologies left by drying drops of different shapes and evaporation profiles. This work is part of a thesis project advised by Tom Witten. It was supported in part by the National Science Foundation's MRSEC Program under Award Number DMR 0820054.

  10. Pressure Drops Due to Silica Scaling

    SciTech Connect

    Brown, K.L.; Freeston, D.H.; Dimas, Z.O.; Slatter, A.

    1995-01-01

    Experience with reinjection returns in many geothermal fields has prompted a move towards injecting waste fluids at some distance from the production field. This means that often, reinjection pipelines cover very long distances. If the waste water in the pipelines is supersaturated with respect to amorphous silica, then the deposition of silica in these pipelines is almost certain. Although the deposit may be of negligible thickness, the inner surface characteristics of the pipe will be different to those of clean mild steel. During a silica scaling experiment. geothermal brine was passed through a series of pipes of different sizes and over a period of three weeks, silica scale formed on the inner surface. The pressure drop along a distance of approximately 5m was measured by a water manometer in all test pipe sections. Significant pressure drop was observed during this time and can be correlated with the increase in the friction factor of the pipe walls due to silica scaling.

  11. Fluid imbalance

    MedlinePlus

    ... up in the body. This is called fluid overload (volume overload). This can lead to edema (excess fluid in ... Water imbalance; Fluid imbalance - dehydration; Fluid buildup; Fluid overload; Volume overload; Loss of fluids; Edema - fluid imbalance; ...

  12. Stability of the shape of a translating viscoelastic drop at low Reynolds number

    NASA Astrophysics Data System (ADS)

    Wu, H.; Haj-Hariri, H.; Borhan, A.

    2012-11-01

    We examine the stability of the shape of a viscoelastic drop translating in an immiscible, otherwise quiescent Newtonian fluid at low Reynolds number. Non-Newtonian stresses in the drop phase are characterized by the finitely extensible nonlinear elastic-Chilcott-Rallison model. A boundary integral method is used to numerically examine the time-evolution of initially perturbed drop shapes over a range of dimensionless parameters. For sufficiently small capillary numbers, the drop achieves an oblate spheroidal steady shape. For large initial deformations or capillary numbers, however, the drop deforms continuously and eventually breaks up through either the formation of an elongated tail or the development of a re-entrant cavity at its trailing end. These mechanisms of drop breakup are qualitatively similar to those reported earlier for Newtonian drops [C. J. Koh and L. G. Leal, Phys. Fluids A 1, 1309 (1989), 10.1063/1.857359; C. Pozrikidis, J. Fluid Mech. 210, 1 (1990), 10.1017/S0022112090001203; H. A. Stone, Annu. Rev. Fluid Mech. 26, 65 (1994), 10.1146/annurev.fl.26.010194.000433]. Compared to the case of a Newtonian drop, drop phase elasticity is found to have a stabilizing (destabilizing) effect for initially oblate (prolate) shape perturbations, due to the development of polymeric stresses caused by deformation of polymer chains in alignment with streamlines of the flow. Polymer viscosity has a strong influence on the stability of the shape of drops, whereas polymer relaxation time and extensibility have relatively weak influences.

  13. Simulations of surfactant-laden drops rising in a density-stratified medium

    NASA Astrophysics Data System (ADS)

    Martin, David W.; Blanchette, François

    2017-02-01

    We present simulations of the effects of insoluble surfactant on drops rising in unstratified media and density-stratified media. We consider an oil drop rising in water, and we track surfactant concentration on the drop surface. We first consider a drop coated with insoluble surfactant rising through an unstratified ambient. The drop speed is computed for various Marangoni numbers, and inertial and surface diffusion effects are also examined. In the second setup, we compare clean and contaminated drops rising through a linear density-stratified fluid. The entrained buoyancy is computed for various density gradients, and the effects of inertia and Marangoni number are characterized. We find that the entrained fluid slows the drop in a manner comparable to a vertical shift in the ambient density gradient.

  14. Drop shape visualization and contact angle measurement on curved surfaces.

    PubMed

    Guilizzoni, Manfredo

    2011-12-01

    The shape and contact angles of drops on curved surfaces is experimentally investigated. Image processing, spline fitting and numerical integration are used to extract the drop contour in a number of cross-sections. The three-dimensional surfaces which describe the surface-air and drop-air interfaces can be visualized and a simple procedure to determine the equilibrium contact angle starting from measurements on curved surfaces is proposed. Contact angles on flat surfaces serve as a reference term and a procedure to measure them is proposed. Such procedure is not as accurate as the axisymmetric drop shape analysis algorithms, but it has the advantage of requiring only a side view of the drop-surface couple and no further information. It can therefore be used also for fluids with unknown surface tension and there is no need to measure the drop volume. Examples of application of the proposed techniques for distilled water drops on gemstones confirm that they can be useful for drop shape analysis and contact angle measurement on three-dimensional sculptured surfaces.

  15. Axisymmetric model of drop spreading on a horizontal surface

    NASA Astrophysics Data System (ADS)

    Mistry, Aashutosh; Muralidhar, K.

    2015-09-01

    Spreading of an initially spherical liquid drop over a textured surface is analyzed by solving an integral form of the governing equations. The mathematical model extends Navier-Stokes equations by including surface tension at the gas-liquid boundary and a force distribution at the three phase contact line. While interfacial tension scales with drop curvature, the motion of the contact line depends on the departure of instantaneous contact angle from its equilibrium value. The numerical solution is obtained by discretizing the spreading drop into disk elements. The Bond number range considered is 0.01-1. Results obtained for sessile drops are in conformity with limiting cases reported in the literature [J. C. Bird et al., "Short-time dynamics of partial wetting," Phys. Rev. Lett. 100, 234501 (2008)]. They further reveal multiple time scales that are reported in experiments [K. G. Winkels et al., "Initial spreading of low-viscosity drops on partially wetting surfaces," Phys. Rev. E 85, 055301 (2012) and A. Eddi et al., "Short time dynamics of viscous drop spreading," Phys. Fluids 25, 013102 (2013)]. Spreading of water and glycerin drops over fully and partially wetting surfaces is studied in terms of excess pressure, wall shear stress, and the dimensions of the footprint. Contact line motion is seen to be correctly captured in the simulations. Water drops show oscillations during spreading while glycerin spreads uniformly over the surface.

  16. CFD evaluation of drop retraction methods for the measurement of interfacial tension of surfactant-laden drops.

    PubMed

    Velankar, Sachin; Zhou, Hua; Jeon, Hyun Kyoung; Macosko, Christopher W

    2004-04-01

    Drop retraction methods are popular means of measuring the interfacial tension between immiscible polymers. Experiments show that two different drop retraction methods, imbedded fiber retraction (IFR) and deformed drop retraction (DDR), give inconsistent results when a surfactant is present on the surface of the drop. These inconsistencies are deemed to be due to dilution of the surfactant and due to gradients in interfacial concentration of surfactant along the drop surface. This physical picture is quantified for the simple case of a Newtonian drop in a Newtonian matrix, with an insoluble, nondiffusive surfactant at the interface. The drop is deformed in computational fluid dynamics simulations by shearing the matrix, and then allowed to retract. Dilution and interfacial tension gradients effects are found to be especially large at the early stages of retraction, making IFR unsuitable for measuring the interfacial tension of surfactant-laden interfaces. The effects of surfactant dilution and gradients are found to persist even at late stages of retraction, causing the DDR method to underestimate the equilibrium interfacial tension significantly. The largest underestimates occur when the drop viscosity is lower than the matrix viscosity.

  17. Microwave fluid flow meter

    DOEpatents

    Billeter, Thomas R.; Philipp, Lee D.; Schemmel, Richard R.

    1976-01-01

    A microwave fluid flow meter is described utilizing two spaced microwave sensors positioned along a fluid flow path. Each sensor includes a microwave cavity having a frequency of resonance dependent upon the static pressure of the fluid at the sensor locations. The resonant response of each cavity with respect to a variation in pressure of the monitored fluid is represented by a corresponding electrical output which can be calibrated into a direct pressure reading. The pressure drop between sensor locations is then correlated as a measure of fluid velocity. In the preferred embodiment the individual sensor cavities are strategically positioned outside the path of fluid flow and are designed to resonate in two distinct frequency modes yielding a measure of temperature as well as pressure. The temperature response can then be used in correcting for pressure responses of the microwave cavity encountered due to temperature fluctuations.

  18. System for Manipulating Drops and Bubbles Using Acoustic Radiation Pressure

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard C. (Inventor)

    1999-01-01

    The manipulation and control of drops of liquid and gas bubbles is achieved using high intensity acoustics in the form of and/or acoustic radiation pressure and acoustic streaming. generated by a controlled wave emission from a transducer. Acoustic radiation pressure is used to deploy or dispense drops into a liquid or a gas or bubbles into a liquid at zero or near zero velocity from the discharge end of a needle such as a syringe needle. Acoustic streaming is useful in manipulating the drop or bubble during or after deployment. Deployment and discharge is achieved by focusing the acoustic radiation pressure on the discharge end of the needle, and passing the acoustic waves through the fluid in the needle. through the needle will itself, or coaxially through the fluid medium surrounding the needle. Alternatively, the acoustic waves can be counter-deployed by focusing on the discharge end of the needle from a transducer axially aligned with the needle, but at a position opposite the needle, to prevent premature deployment of the drop or bubble. The acoustic radiation pressure can also be used for detecting the presence or absence of a drop or a bubble at the tip of a needle or for sensing various physical characteristics of the drop or bubble such as size or density.

  19. Ultrasonic characterization of single drops of liquids

    DOEpatents

    Sinha, D.N.

    1998-04-14

    Ultrasonic characterization of single drops of liquids is disclosed. The present invention includes the use of two closely spaced transducers, or one transducer and a closely spaced reflector plate, to form an interferometer suitable for ultrasonic characterization of droplet-size and smaller samples without the need for a container. The droplet is held between the interferometer elements, whose distance apart may be adjusted, by surface tension. The surfaces of the interferometer elements may be readily cleansed by a stream of solvent followed by purified air when it is desired to change samples. A single drop of liquid is sufficient for high-quality measurement. Examples of samples which may be investigated using the apparatus and method of the present invention include biological specimens (tear drops; blood and other body fluid samples; samples from tumors, tissues, and organs; secretions from tissues and organs; snake and bee venom, etc.) for diagnostic evaluation, samples in forensic investigations, and detection of drugs in small quantities. 5 figs.

  20. Technology of eye drops containing aloe (Aloe arborescens Mill.--Liliaceae) and eye drops containing both aloe and neomycin sulphate.

    PubMed

    Kodym, A; Marcinkowski, A; Kukuła, H

    2003-01-01

    Eye drops made of aloe are a sterile, aqueous extract of fresh leaves of Aloe arborescens Mill., containing necessary additives and neomycin sulphate. The aim of the studies was to establish the technology of eye drops containing biologically active aloe substances and those containing both chemical constituents of aloe and neomycin sulphate. Within the studies, the formulary content and the way of preparing eye drops were determined, criteria were defined and methods of qualitative assessment of drops were proposed. On the basis of the proposed analytical methods, the physicochemical and microbiological stability of the eye drops stored at a temperature of 20-25 degrees C was studied. As the criteria of qualitative assessment of the eye drops, the following analyses were considered: sterility, appearance of the eye drops (clarity), pH, osmotic pressure, density, viscosity, TLC analysis, content of aloenin and aloin, studies of anti-microbial activity of neomycin in the drops, and preservative efficiency of thiomersal in the eye drops. The studies showed that the additives such as: sodium chloride, benzalkonium chloride, chlorhexidine diacetate and digluconate, phenylmercuric borate and Nipagins M and P could not be used to prepare the eye drops because they were involved in pharmaceutical interactions with chemical constituents of aloe in the eye drops. The eye drops containing: aqueous extract of fresh leaves of aloe, boric acid, thiomersal, sodium pyrosulphite, disodium EDTA, beta-phenylethyl alcohol and neomycin sulphate, both freshly prepared and after two years of storage, met the requirements of the Polish Pharmacopoeia (PPh V) mentioned in the monograph Guttae ophthalmicae. They were sterile, clear, their osmotic pressure approximated the osmotic pressure of lacrimal fluid and they were characterized by appropriate pH. Aloenin in the drops was much more stable than aloin. Neomycin after two years of storage retained almost 98% of its starting antimicrobial

  1. Coalescence and noncoalescence of sessile drops: impact of surface forces.

    PubMed

    Karpitschka, Stefan; Hanske, Christoph; Fery, Andreas; Riegler, Hans

    2014-06-17

    Due to capillarity, sessile droplets of identical liquids will instantaneously fuse when they come in contact at their three-phase lines. However, with drops of different, completely miscible liquids, instantaneous coalescence can be suppressed. Instead, the drops remain in a state of noncoalescence for some time, with the two drop bodies connected only by a thin neck. The reason for this noncoalescence is the surface tension difference, Δγ, between the liquids. If Δγ is sufficiently large, then it induces a sufficiently strong Marangoni flow, which keeps the main drop bodies temporarily separated. Studies with spreading drops have revealed that the boundary between instantaneous coalescence and noncoalescence is sharp (Karpitschka, S.; Riegler, H. J. Fluid. Mech. 2014, 743, R1). The boundary is a function of two parameters only: Δγ and Θ(a), the arithmetic mean of the contact angles in the moment of drop-drop contact. It appears plausible that surface forces (the disjoining pressure) could also influence the coalescence behavior. However, in experiments with spreading drops, surface forces always promote coalescence and their influence might be obscured. Therefore, we present here coalescence experiments with partially wetting liquids and compare the results to the spreading case. We adjust different equilibrium contact angles (i.e., different surface forces) with different substrate surface coatings. As for spreading drops, we observe a sharp boundary between regimes of coalescence and noncoalescence. The boundary follows the same power law relation for both partially and completely wetting cases. Therefore, we conclude that surface forces have no significant, explicit influence on the coalescence behavior of sessile drops from different miscible liquids.

  2. Deposits of drying drops of a nanotube suspension

    NASA Astrophysics Data System (ADS)

    Vargas, Minerva; Limon, Caleb; Sarmiento, Oscar; Hernandez-Cruz, Guillermo; Ramos, Eduardo; Rincon, Marina

    2010-11-01

    We have made observations of the pattern formed by deposits of an evaporating sessile drop of a carbon nanotube suspension. The nanotubes are chains of carbon molecules, 2 nm diameter and approximately 15 micrometers long.The suspension concentration is 0.25 mg/ml and initially, the drops volume is 2 μl. Nanotubes are transported by the flow generated by evaporation at the surface of the drops and the resulting patterns are the result of the drag of the filaments by the fluid motion. The pattern observed is composed of a circular band with several (order ten) spots with higher concentration of nanotubes. Also, the inner rim of the band displays a higher concentration of nanotubes. In contrast to similar observations where the suspensions are prepared with microspheres, no ring formation at the outer edge of the initial footprint of the drop (coffee effect) is clearly identified. Our observations are interpreted in terms of existing theories.

  3. Initiation of liquid-solid contact beneath an impacting drop

    NASA Astrophysics Data System (ADS)

    Rubinstein, Shmuel; Kolinski, John

    2015-11-01

    Before an impacting drop contacts the solid surface it must first drain the air beneath it. As a prelude to wetting, before any contact occurs, the impinging liquid confines the intervening air into a nanometers-thin film. Once liquid-solid contact initiates by the spontaneous formation of a liquid bridge, the fluid rapidly wicks through the thin film of air, permanently binding the drop to the surface. Here, we experimentally examine these initial stages in the formation of the liquid solid contact beneath the impacting drop. Fast TIR microscopy enables unprecedented spatial and temporal resolution of the wetting process beneath the impacting drop and permits 3-dimensional imaging of the real contact line as well as nanometer-resolution of the thin film of air separating the liquid from the solid.

  4. Origin and dynamics of vortex rings in drop splashing

    SciTech Connect

    Lee, Ji San; Park, Su Ji; Lee, Jun Ho; Weon, Byung Mook; Fezzaa, Kamel; Je, Jung Ho

    2015-09-04

    A vortex is a flow phenomenon that is very commonly observed in nature. More than a century, a vortex ring that forms during drop splashing has caught the attention of many scientists due to its importance in understanding fluid mixing and mass transport processes. However, the origin of the vortices and their dynamics remain unclear, mostly due to the lack of appropriate visualization methods. Here, with ultrafast X-ray phase-contrast imaging, we show that the formation of vortex rings originates from the energy transfer by capillary waves generated at the moment of the drop impact. Interestingly, we find a row of vortex rings along the drop wall, as demonstrated by a phase diagram established here, with different power-law dependencies of the angular velocities on the Reynolds number. These results provide important insight that allows understanding and modelling any type of vortex rings in nature, beyond just vortex rings during drop splashing.

  5. Origin and dynamics of vortex rings in drop splashing

    DOE PAGES

    Lee, Ji San; Park, Su Ji; Lee, Jun Ho; ...

    2015-09-04

    A vortex is a flow phenomenon that is very commonly observed in nature. More than a century, a vortex ring that forms during drop splashing has caught the attention of many scientists due to its importance in understanding fluid mixing and mass transport processes. However, the origin of the vortices and their dynamics remain unclear, mostly due to the lack of appropriate visualization methods. Here, with ultrafast X-ray phase-contrast imaging, we show that the formation of vortex rings originates from the energy transfer by capillary waves generated at the moment of the drop impact. Interestingly, we find a row ofmore » vortex rings along the drop wall, as demonstrated by a phase diagram established here, with different power-law dependencies of the angular velocities on the Reynolds number. These results provide important insight that allows understanding and modelling any type of vortex rings in nature, beyond just vortex rings during drop splashing.« less

  6. Origin and dynamics of vortex rings in drop splashing

    PubMed Central

    Lee, Ji San; Park, Su Ji; Lee, Jun Ho; Weon, Byung Mook; Fezzaa, Kamel; Je, Jung Ho

    2015-01-01

    A vortex is a flow phenomenon that is very commonly observed in nature. More than a century, a vortex ring that forms during drop splashing has caught the attention of many scientists due to its importance in understanding fluid mixing and mass transport processes. However, the origin of the vortices and their dynamics remain unclear, mostly due to the lack of appropriate visualization methods. Here, with ultrafast X-ray phase-contrast imaging, we show that the formation of vortex rings originates from the energy transfer by capillary waves generated at the moment of the drop impact. Interestingly, we find a row of vortex rings along the drop wall, as demonstrated by a phase diagram established here, with different power-law dependencies of the angular velocities on the Reynolds number. These results provide important insight that allows understanding and modelling any type of vortex rings in nature, beyond just vortex rings during drop splashing. PMID:26337704

  7. Critical point wetting drop tower experiment

    NASA Technical Reports Server (NTRS)

    Kaukler, William F.

    1990-01-01

    The 100 m Drop Tower at NASA-Marshall was used to provide the step change in acceleration from 1.0 to 0.0005 g. An inter-fluid meniscus oscillates vertically within a cylindrical container when suddenly released from earth's gravity and taken into a microgravity environment. Oscillations damp out from energy dissipative mechanisms such as viscosity and interfacial friction. Damping of the oscillations by the later mechanism is affected by the nature of the interfacial junction between the fluid-fluid interface and the container wall. In earlier stages of the project, the meniscus shape which developed during microgravity conditions was applied to evaluations of wetting phenomena near the critical temperature. Variations in equilibrium contact angle against the container wall were expected to occur under critical wetting conditions. However, it became apparent that the meaningful phenomenon was the damping of interfacial oscillations. This latter concept makes up the bulk of this report. Perfluoromethyl cyclohexane and isopropanol in glass were the materials used for the experiment. The wetting condition of the fluids against the wall changes at the critical wetting transition temperature. This change in wetting causes a change in the damping characteristics of the interfacial excursions during oscillation and no measurable change in contact angle. The effect of contact line friction measured above and below the wetting transition temperature was to increase the period of vertical oscillation for the vapor-liquid interface when below the wetting transition temperature.

  8. Bed of polydisperse viscous spherical drops under thermocapillary effects

    NASA Astrophysics Data System (ADS)

    Sharanya, V.; Raja Sekhar, G. P.; Rohde, Christian

    2016-08-01

    Viscous flow past an ensemble of polydisperse spherical drops is investigated under thermocapillary effects. We assume that the collection of spherical drops behaves as a porous media and estimates the hydrodynamic interactions analytically via the so- called cell model that is defined around a specific representative particle. In this method, the hydrodynamic interactions are assumed to be accounted by suitable boundary conditions on a fictitious fluid envelope surrounding the representative particle. The force calculated on this representative particle will then be extended to a bed of spherical drops visualized as a Darcy porous bed. Thus, the "effective bed permeability" of such a porous bed will be computed as a function of various parameters and then will be compared with Carman-Kozeny relation. We use cell model approach to a packed bed of spherical drops of uniform size (monodisperse spherical drops) and then extend the work for a packed bed of polydisperse spherical drops, for a specific parameters. Our results show a good agreement with the Carman-Kozeny relation for the case of monodisperse spherical drops. The prediction of overall bed permeability using our present model agrees well with the Carman-Kozeny relation when the packing size distribution is narrow, whereas a small deviation can be noted when the size distribution becomes broader.

  9. Internal flow measurements of drop impacting a solid surface

    NASA Astrophysics Data System (ADS)

    Kumar, S. Santosh; Karn, Ashish; Arndt, Roger E. A.; Hong, Jiarong

    2017-03-01

    Understanding the fundamental physical process involved in drop impacts is important for a variety of engineering and scientific applications. Despite exhaustive research efforts on the dynamics of drop morphology upon impact, very few studies investigate the fluid dynamics induced within a drop upon impact. This study employs planar particle image velocimetry (PIV) with fluorescent particles to quantify the internal flow field of a drop impact on a solid surface. The image distortion caused by the curved liquid-air interface at the drop boundary is corrected using a ray-tracing algorithm. PIV analysis using the corrected images has yielded interesting insights into the flow initiated within a drop upon impact. Depending on the pre-impact conditions, characterized by impact number, different vortex modes are observed in the recoil phase of the drop impact. Further, the strength of these vortices and the kinetic energy of the internal flow field have been quantified. Our studies show a consistent negative power law correlation between vortex strength, internal kinetic energy and the impact number.

  10. Skating on a Film of Air: Drops Impacting on a Surface

    NASA Astrophysics Data System (ADS)

    Kolinski, John M.; Rubinstein, Shmuel M.; Mandre, Shreyas; Brenner, Michael P.; Weitz, David A.; Mahadevan, L.

    2012-02-01

    The commonly accepted description of drops impacting on a surface typically ignores the essential role of the air that is trapped between the impacting drop and the surface. Here we describe a new imaging modality that is sensitive to the behavior right at the surface. We show that a very thin film of air, only a few tens of nanometers thick, remains trapped between the falling drop and the surface as the drop spreads. The thin film of air serves to lubricate the drop enabling the fluid to skate on the air film laterally outward at surprisingly high velocities, consistent with theoretical predictions. Eventually this thin film of air breaks down as the fluid wets the surface via a spinodal-like mechanism. Our results show that the dynamics of impacting drops are much more complex than previously thought, with a rich array of unexpected phenomena that require rethinking classic paradigms.

  11. Pressure drop and He II flow through fine mesh screens

    NASA Technical Reports Server (NTRS)

    Maddocks, J. R.; Van Sciver, S. W.

    1989-01-01

    Fluid acquisition systems for He II transfer devices will utilize gallery arms to ensure that the fluid encounters the pump inlet. In near term experiments such as Superfluid Helium on Orbit Transfer (SHOOT), the preferred configuration consists of several rectangular channels which have one side made from a Dutch weave stainless steel screen having 325 x 2300 wires per inch. The effective pore diameter for this screen is about 5 microns. The present paper reports on measurements of pressure drop across a screen when it is subjected to a flow of liquid helium. The experiment measures the time rate of change of the level in two different helium reservoirs connected by a screen-blocked channel. Results with normal helium are compared with predictions based on the Armour-Cannon (1968) equations. The He II data show considerable deviation from the classical result. A discussion of the He II pressure drop results in terms of two fluid hydrodynamics is included.

  12. Instant freezing of impacting wax drops

    NASA Astrophysics Data System (ADS)

    Ponomarenko, Alexandre; Virot, Emmanuel; Rubinstein, Shmuel

    2015-11-01

    We present the impact of hot liquid drops of wax on surfaces whose temperature is below the solidifying temperature of the drops. During the fall the drops remain mostly liquid, but upon impact, their temperature quickly decreases resulting in the solidification of the drop. Depending on the impact energy, drops size and the temperature difference between the drop and the surface this results in plethora of solid shapes: simple lenses, triangular drops, spherical caps and popped popcorn shapes.

  13. Pool impacts of Leidenfrost drop

    NASA Astrophysics Data System (ADS)

    Darbois Texier, Baptiste; Maquet, Laurent; Dorbolo, Stephane; Dehandschoewercker, Eline; Pan, Zhao; Truscott, Tadd

    2015-11-01

    This work concerns the impact of a droplet made of a volatile liquid (typically HFE) on a pool of an other liquid (typically silicone oil) which temperature is above the boiling point of the drop. Depending on the properties of the two liquids and the impacting conditions, four different regimes are observed. For low impacting speeds, the droplet bounces on the surface of the bath and finally levitates above it in a Leidenfrost state. Such a regime occurs as soon as the pool temperature exceeds the boiling point of the drop. This observation means that there is no threshold in temperature for a Leidenfrost effect on a liquid surface contrary to the case of a solid substrate. For intermediate impacting velocities, the pinch-off of the surface of the pool entraps the drop in the liquid bulk. The entrapped drop is separated from the pool by a layer of its own vapour in a similar way of antibulles. For increasing impacting speeds, the vapour layer between the drop and the pool does not hold during the pinch-off event. The contact of the drop with the hot liquid provokes a sudden and intense evaporation. At very large impacting speeds, the drop rapidely contacts the pool, spreads and finally induces a hemi-spherical cavity. In the end, these four different regimes are summarized in a Froud-Weber diagram which boundaries are discussed.

  14. Liquid drops on soft solids

    NASA Astrophysics Data System (ADS)

    Lubbers, Luuk A.; Weijs, Joost H.; Das, Siddhartha; Botto, Lorenzo; Andreotti, Bruno; Snoeijer, Jacco H.

    2014-03-01

    A sessile drop can elastically deform a substrate by the action of capillary forces. The typical size of the deformation is given by the ratio of surface tension and the elastic modulus, γ / E , which can reach up to 10-100 microns for soft elastomers. In this talk we theoretically show that the contact angles of drops on such a surface exhibit two transitions when increasing γ / E : (i) the microsocopic geometry of the contact line first develops a Neumann-like cusp when γ / E is of the order of few nanometers, (ii) the macroscopic angle of the drop is altered only when γ / E reaches the size of the drop. Using the same framework we then show that two neighboring drops exhibit an effective interaction, mediated by the deformation of the elastic medium. This is in analogy to the well-known Cheerios effect, where small particles at a liquid interface attract each other due to the meniscus deformations. Here we reveal the nature of drop-drop interactions on a soft substrate by combining numerical and analytical calculations.

  15. Oscillating drop/bubble tensiometry: effect of viscous forces on the measurement of interfacial tension.

    PubMed

    Freer, E M; Wong, H; Radke, C J

    2005-02-01

    The oscillating drop/bubble technique is increasingly popular for measuring the interfacial dilatational properties of surfactant/polymer-laden fluid/fluid interfaces. A caveat of this technique, however, is that viscous forces are important at higher oscillation frequencies or fluid viscosities; these can affect determination of the interfacial tension. Here, we experimentally quantify the effect of viscous forces on the interfacial-tension measurement by oscillating 100 and 200 cSt poly(dimethylsiloxane) (PDMS) droplets in water at small amplitudes and frequencies ranging between 0.01 and 1 Hz. Due to viscous forces, the measured interfacial tension oscillates sinusoidally with the same frequency as the oscillation of the drop volume. The tension oscillation precedes that of the drop volume, and the amplitude varies linearly with Capillary number, Ca=DeltamuomegaDeltaV/gammaa(2), where Deltamu=mu(D)-mu is the difference between the bulk Newtonian viscosities of the drop and surrounding continuous fluid, omega is the oscillation frequency of the drop, DeltaV is the amplitude of volume oscillation, gamma is the equilibrium interfacial tension between the PDMS drop and water, and a is the radius of the capillary. A simplified model of a freely suspended spherical oscillating-drop well explains these observations. Viscous forces distort the drop shape at Ca>0.002, although this criterion is apparatus dependent.

  16. Dynamics of drops – Formation, growth, oscillation, detachment, and coalescence.

    PubMed

    Karbaschi, M; Taeibi Rahni, M; Javadi, A; Cronan, C L; Schano, K H; Faraji, S; Won, J Y; Ferri, J K; Krägel, J; Miller, R

    2015-08-01

    Single drops or bubbles are frequently used for the characterization of liquid-fluid interfaces. Their advantage is the small volume and the various protocols of their formation. Thus, several important methods are based on single drops and bubbles, such as capillary pressure and profile analysis tensiometry. However, these methods are often applied under dynamic conditions, although their principles are defined under equilibrium conditions. Thus, specific attention has to be paid when these methods are used beyond certain limits. In many cases, computational fluid dynamics (CFD) simulations have allowed researchers, to extend these limits and to gain important information on the interfacial dynamics. Examples discussed here are the capillary pressure tensiometry used for short time and profile analysis tensiometry for long time dynamic interfacial tension measurements, the oscillating drop methods for measuring dilational visco-elasticity. For measuring the coalescence of two drops the liquid dynamics of the subsequently formed liquid bridges have to be considered. In this paper, a thorough review of important experimental and computational findings, related to the dynamics of drops, including its formation, growth, oscillation, detachment, and coalescence is presented. Emphasis is however on some selected important developments. In addition, the paper tries to predict the main directions of advancement in interfacial research for the near future.

  17. Local analysis of the contact region of an evaporating sessile drop

    NASA Astrophysics Data System (ADS)

    Morris, S. J. S.

    2014-11-01

    In experiments by Guéna et al. (2007), a drop of perfectly wetting pure liquid evaporates from a non-heated substrate at a rate controlled by vapour diffusion. The drop spreads until reaching a radius a determined by initial drop volume; the apparent contact line then reverses direction. The apparent contact angle measured at reversal was found experimentally to vary as a - 1 / 6 for a < 1 mm (about); for larger drops θ decreases more strongly. Local analysis (Morris, J. Fluid Mech. 739, 308 (2014)) predicts that θ ~a - 1 / 6 ; for the smaller drops obeying the 1/6th rule, predicted values agree with experiment to within 10-30%. Though the behaviour of drops smaller than the capillary length thus appears to be understood, that of larger drops is not.

  18. Orion Capsule Mockup is Dropped

    NASA Video Gallery

    An Orion capsule mockup is dropped from a plane 25,000 feet above the Arizona desert to test its parachute design. Orion will return to Earth at speeds faster than previous human spacecraft, and wi...

  19. Thermocapillary motion of deformable drops at finite Reynolds and Marangoni numbers

    NASA Astrophysics Data System (ADS)

    Haj-Hariri, H.; Shi, Q.; Borhan, A.

    1997-04-01

    We present the results of numerical simulations of the three-dimensional thermocapillary motion of deformable viscous drops under the influence of a constant temperature gradient within a second liquid medium. In particular, we examine the effects of shape deformations and convective transport of momentum and energy on the migration velocity of the drop. A numerical method based on a continuum model for the fluid-fluid interface is used to account for finite drop deformations. An oct-tree adaptive grid refinement scheme is integrated into the numerical method in order to track the interface without the need for interface reconstruction. Interface deformations arising from the convection of energy at small Reynolds numbers are found to be negligible. On the other hand, deformations of the drop shape due to inertial effects, though small in magnitude, are found to retard the motion of the drop. The steady drop shapes are found to resemble oblate or prolate spheroids without fore and aft symmetry, with the direction of elongation of the drop depending on the value of the density ratio between the two phases. As in the case of a gas bubble, convection of energy is shown to retard the thermocapillary motion of a viscous drop, as the isotherms get wrapped around the front surface of the drop and effectively reduce the surface temperature gradient which drives the motion. The effect of inertia on the mobility of viscous drops is found to be weaker than that in the case of gas bubbles.

  20. Unsteady Thermocapillary Migration of Isolated Drops in Creeping Flow

    NASA Technical Reports Server (NTRS)

    Dill, Loren H.; Balasubramaniam, R.

    1992-01-01

    The problem of an isolated immiscible drop that slowly migrates due to unsteady thermocapillary stresses is considered. All physical properties except for interfacial tension are assumed constant for the two Newtonian fluids. Explicit expressions are found for the migration rate and stream functions in the Laplace domain. The resulting microgravity theory is useful, e.g., in predicting the distance a drop will migrate due to an impulsive interfacial temperature gradient as well as the time required to attain steady flow conditions from an initially resting state.

  1. Structure and Dynamics of Interfaces: Drops and Films

    NASA Technical Reports Server (NTRS)

    Mann, J. Adin, Jr.; Mann, Elizabeth K.; Meyer, William V.; Neumann, A. Wilhelm; Tavana, Hossein

    2015-01-01

    We aim to acquire measurements of the structure and dynamics of certain liquid-fluid interfaces using an ensemble of techniques in collaboration: (1) Total internal reflection (TIR) Surface light scattering spectroscopy (SLSS), (2) Brewster angle microscopy (BAM), and (3) Drop-shape analysis. SLSS and BAM can be done on a shared interfacial footprint. Results using a 50-50 mixture of pentane-isohexane, which extends the range of NASA's Confined Vapor Bubble (CVB) experiment, yield surface tension results that differ from the expected Langmuir Fit. These results were confirmed using both the SLSS and drop-shape analysis approaches.

  2. Investigation of Drop Formation by a Vortex Ring in Microgravity

    NASA Technical Reports Server (NTRS)

    Bernal, Luis P.; Maksimovic, Pepi

    1996-01-01

    An investigation of drop formation by a vortex ring propagating through one or more fluid interfaces in microgravity is described. The main goal of the research is to determine the dynamics of drop formation by vortical flows in the capillary limit with large density change across the intel-face. Dimensional analysis shows that in microgravity experiments the capillary limit can be studied using a relatively large vortex ring diameter to facilitate experimental characterization of the interaction. Results obtained in density matched systems are reviewed to illustrate the complex nature of these interactions.

  3. Damping of drop oscillations by surfactants and surface viscosity

    NASA Technical Reports Server (NTRS)

    Rush, Brian M.; Nadim, Ali

    1999-01-01

    An energy equation is derived for the general case of a viscous drop suspended in a viscous medium with surfactants contaminating the interface. It contains terms that clearly identify dissipation contributions from the viscous effects in the bulk fluids, surface shear and dilatational viscosity effects at the interface, and surfactant transport. An efficient boundary integral method is developed which incorporates the effects of a constant surface dilatational viscosity in simulations of an oscillating two-dimensional inviscid drop. Surface dilatational viscosity is shown to have a significant damping effect on the otherwise undamped inviscid oscillations.

  4. Drop shedding by shear flow for hydrophilic to superhydrophobic surfaces.

    PubMed

    Milne, A J B; Amirfazli, A

    2009-12-15

    A balance of surface science and aerodynamic knowledge is brought to bear to elucidate the fundamental parameters determining the incipient motion (runback) for a drop exposed to shearing airflow. It was found that wetting parameters such as contact angle are very influential in determining the minimum required air velocity for drop shedding. On the basis of experimental results for drops of water and hexadecane (0.5-100 microL) on PMMA, Teflon, and a superhydrophobic aluminum surface, an exponential function is proposed that relates the critical air velocity for shedding to the ratio of drop base length to projected area. The results for all of the water systems can be collapsed to self-similar curves by normalization. Results from other researchers also conform to the exponential self-similar functional form proposed. It was shown that the data for hexadecane drops can be matched relatively well to those for water drops by means of a corrective factor based on fluid properties and contact angles. Also, the critical air velocity for shedding from the superhydrophobic surface is seen to be more constant over a range of volumes than for the other surfaces. Finally, contact angle measurements from airflow shedding experiments are compared to measurements made by tilted plate and quasi-static advancing and receding tests. The observed differences between contact angles from different measurement methods show that the transfer of contact angle data among various applications must be done with care.

  5. The oscillations of cylindrical drop under the influence of a nonuniform alternating electric field

    NASA Astrophysics Data System (ADS)

    Alabuzhev, A. A.; Kashina, M. A.

    2016-02-01

    The forced oscillations of incompressible fluid drop under the alternating electric field are considered. In equilibrium, the drop has the form of a cylinder bounded axially parallel solid planes and contact angle is right. The drop is surrounded by an incompressible fluid with another density. The external nonuniform 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 speed of the fast relaxation processes, which frequency is proportional

  6. Forced Oscillations of Supported Drops

    NASA Technical Reports Server (NTRS)

    Wilkes, Edward D.; Basaran, Osman A.

    1996-01-01

    Oscillations of supported liquid drops are the subject of wide scientific interest, with applications in areas as diverse as liquid-liquid extraction, synthesis of ceramic powders, growing of pure crystals in low gravity, and measurement of dynamic surface tension. In this research, axisymmetric forced oscillations of arbitrary amplitude of viscous liquid drops of fixed volume which are pendant from or sessile on a rod with a fixed or moving contact line and surrounded by an inviscid ambient gas are induced by moving the rod in the vertical direction sinusiodally in time. In this paper, a preliminary report is made on the computational analysis of the oscillations of supported drops that have 'clean' interfaces and whose contact lines remain fixed throughout their motions. The relative importance of forcing to damping can be increased by either increasing the amplitude of rod motion A or Reynolds number Re. It is shown that as the ratio of forcing to damping rises, for drops starting from an initial rest state a sharp increase in deformation can occur when they are forced to oscillate in the vicinity of their resonance frequencies, indicating the incipience of hysteresis. However, it is also shown that the existence of a second stable limit cycle and the occurrence of hysteresis can be observed if the drop is subjected to a so-called frequency sweep, where the forcing frequency is first increased and then decreased over a suitable range. Because the change in drop deformation response is abrupt in the vicinity of the forcing frequencies where hysteresis occurs, it should be possible to exploit the phenomenon to accurately measure the viscosity and surface tension of the drop liquid.

  7. Bubble and Drop Nonlinear Dynamics experiment

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Bubble and Drop Nonlinear Dynamics (BDND) experiment was designed to improve understanding of how the shape and behavior of bubbles respond to ultrasound pressure. By understanding this behavior, it may be possible to counteract complications bubbles cause during materials processing on the ground. This 12-second sequence came from video downlinked from STS-94, July 5 1997, MET:3/19:15 (approximate). The BDND guest investigator was Gary Leal of the University of California, Santa Barbara. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced fluid dynamics experiments will be a part of investigations plarned for the International Space Station. (189KB JPEG, 1293 x 1460 pixels; downlinked video, higher quality not available) The MPG from which this composite was made is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300163.html.

  8. The dynamics of free liquid drops

    NASA Technical Reports Server (NTRS)

    Wang, T. G.; Trinh, E. H.; Croonquist, A. P.; Elleman, D. D.

    1988-01-01

    The behavior of rotating and oscillating free liquid drops was studied by many investigators theoretically for many years. More recent numerical treatments have yielded predictions which are yet to be verified experimentally. The purpose is to report the results of laboratory work as well as that of the experiments carried out in space during the flight of Spacelab 3, and to compare it with the existing theoretical studies. Ground-based experiments were attempted as a first approximation to the ideal boundary conditions used by the theoretical treatments by neutralizing the overwhelming effects of the Earth's gravitational field with an outside supporting liquid and with the use of levitation technology. The viscous and inertial loading of such a suspending fluid was found to profoundly effect the results, but the information thus gathered has emphasized the uniqueness of the experimental data obtained in the low-gravity environment of space.

  9. Drop Impact on to Moving Liquid Pools

    NASA Astrophysics Data System (ADS)

    Muñoz-Sánchez, Beatriz Natividad; Castrejón-Pita, José Rafael; Castrejón-Pita, Alfonso Arturo; Hutchings, Ian M.

    2014-11-01

    The deposition of droplets on to moving liquid substrates is an omnipresent situation both in nature and industry. A diverse spectrum of phenomena emerges from this simple process. In this work we present a parametric experimental study that discerns the dynamics of the impact in terms of the physical properties of the fluid and the relative velocity between the impacting drop and the moving liquid pool. The behaviour ranges from smooth coalescence (characterized by little mixing) to violent splashing (generation of multiple satellite droplets and interfacial vorticity). In addition, transitional regimes such as bouncing and surfing are also found. We classify the system dynamics and show a parametric diagram for the conditions of each regime. This work was supported by the EPSRC (Grant EP/H018913/1), the Royal Society, Becas Santander Universidades and the International Relationships Office of the University of Extremadura.

  10. Picoinjection of Microfluidic Drops Without Metal Electrodes

    PubMed Central

    O'Donovan, Brian; Tran, Tuan; Sciambi, Adam; Abate, Adam

    2014-01-01

    Existing methods for picoinjecting reagents into microfluidic drops require metal electrodes integrated into the microfluidic chip. The integration of these electrodes adds cumbersome and error-prone steps to the device fabrication process. We have developed a technique that obviates the needs for metal electrodes during picoinjection. Instead, it uses the injection fluid itself as an electrode, since most biological reagents contain dissolved electrolytes and are conductive. By eliminating the electrodes, we reduce device fabrication time and complexity, and make the devices more robust. In addition, with our approach, the injection volume depends on the voltage applied to the picoinjection solution; this allows us to rapidly adjust the volume injected by modulating the applied voltage. We demonstrate that our technique is compatible with reagents incorporating common biological compounds, including buffers, enzymes, and nucleic acids. PMID:24797680

  11. Rheological properties, shape oscillations, and coalescence of liquid drops with surfactants

    NASA Technical Reports Server (NTRS)

    Apfel, R. E.; Holt, R. G.

    1990-01-01

    A method was developed to deduce dynamic interfacial properties of liquid drops. The method involves measuring the frequency and damping of free quadrupole oscillations of an acoustically levitated drop. Experimental results from pure liquid-liquid systems agree well with theoretical predictions. Additionally, the effects of surfactants is considered. Extension of these results to a proposed microgravity experiment on the drop physics module (DPM) in USML-1 are discussed. Efforts are also underway to model the time history of the thickness of the fluid layer between two pre-coalescence drops, and to measure the film thickness experimentally. Preliminary results will be reported, along with plans for coalescence experiments proposed for USML-1.

  12. Lattice Boltzmann Models for Multicomponent Fluids

    DTIC Science & Technology

    2007-11-02

    between multiphase fluids. Two specific physical problems investigated: the shape of a sessile drop on a horizontal surface subjected to a gravitational field, and the effect of surface tension on contact angle .

  13. Stretching and squeezing of sessile dielectric drops by the optical radiation pressure.

    PubMed

    Chraïbi, Hamza; Lasseux, Didier; Arquis, Eric; Wunenburger, Régis; Delville, Jean-Pierre

    2008-06-01

    We study numerically the deformation of sessile dielectric drops immersed in a second fluid when submitted to the optical radiation pressure of a continuous Gaussian laser wave. Both drop stretching and drop squeezing are investigated at steady state where capillary effects balance the optical radiation pressure. A boundary integral method is implemented to solve the axisymmetric Stokes flow in the two fluids. In the stretching case, we find that the drop shape goes from prolate to near-conical for increasing optical radiation pressure whatever the drop to beam radius ratio and the refractive index contrast between the two fluids. The semiangle of the cone at equilibrium decreases with the drop to beam radius ratio and is weakly influenced by the index contrast. Above a threshold value of the radiation pressure, these "optical cones" become unstable and a disruption is observed. Conversely, when optically squeezed, the drop shifts from an oblate to a concave shape leading to the formation of a stable "optical torus." These findings extend the electrohydrodynamics approach of drop deformation to the much less investigated "optical domain" and reveal the openings offered by laser waves to actively manipulate droplets at the micrometer scale.

  14. Drop spreading with random viscosity

    NASA Astrophysics Data System (ADS)

    Xu, Feng; Jensen, Oliver E.

    2016-10-01

    We examine theoretically the spreading of a viscous liquid drop over a thin film of uniform thickness, assuming the liquid's viscosity is regulated by the concentration of a solute that is carried passively by the spreading flow. The solute is assumed to be initially heterogeneous, having a spatial distribution with prescribed statistical features. To examine how this variability influences the drop's motion, we investigate spreading in a planar geometry using lubrication theory, combining numerical simulations with asymptotic analysis. We assume diffusion is sufficient to suppress solute concentration gradients across but not along the film. The solute field beneath the bulk of the drop is stretched by the spreading flow, such that the initial solute concentration immediately behind the drop's effective contact lines has a long-lived influence on the spreading rate. Over long periods, solute swept up from the precursor film accumulates in a short region behind the contact line, allowing patches of elevated viscosity within the precursor film to hinder spreading. A low-order model provides explicit predictions of the variances in spreading rate and drop location, which are validated against simulations.

  15. Static Magnetowetting of Ferrofluid Drops.

    PubMed

    Rigoni, Carlo; Pierno, Matteo; Mistura, Giampaolo; Talbot, Delphine; Massart, René; Bacri, Jean-Claude; Abou-Hassan, Ali

    2016-08-02

    We report results of a comprehensive study of the wetting properties of sessile drops of ferrofluid water solutions at various concentrations deposited on flat substrates and subjected to the action of permanent magnets of different sizes and strengths. The amplitude and the gradient of the magnetic field experienced by the ferrofluid are changed by varying the magnets and their distance to the surface. Magnetic forces up to 100 times the gravitational one and magnetic gradients up to 1 T/cm are achieved. A rich phenomenology is observed, ranging from flattened drops caused by the magnetic attraction to drops extended normally to the substrate because of the normal traction of the magnetic field. We find that the former effect can be conveniently described in terms of an effective Bond number that compares the effective drop attraction with the capillary force, whereas the drop's vertical elongation is effectively expressed by a dimensionless number S, which compares the pressure jump at the ferrofluid interface because of the magnetization with the capillary pressure.

  16. Drop Spreading with Random Viscosity

    NASA Astrophysics Data System (ADS)

    Xu, Feng; Jensen, Oliver

    2016-11-01

    Airway mucus acts as a barrier to protect the lung. However as a biological material, its physical properties are known imperfectly and can be spatially heterogeneous. In this study we assess the impact of these uncertainties on the rate of spreading of a drop (representing an inhaled aerosol) over a mucus film. We model the film as Newtonian, having a viscosity that depends linearly on the concentration of a passive solute (a crude proxy for mucin proteins). Given an initial random solute (and hence viscosity) distribution, described as a Gaussian random field with a given correlation structure, we seek to quantify the uncertainties in outcomes as the drop spreads. Using lubrication theory, we describe the spreading of the drop in terms of a system of coupled nonlinear PDEs governing the evolution of film height and the vertically-averaged solute concentration. We perform Monte Carlo simulations to predict the variability in the drop centre location and width (1D) or area (2D). We show how simulation results are well described (at much lower computational cost) by a low-order model using a weak disorder expansion. Our results show for example how variability in the drop location is a non-monotonic function of the solute correlation length increases. Engineering and Physical Sciences Research Council.

  17. Effect of External Pressure Drop on Loop Heat Pipe Operating Temperature

    NASA Technical Reports Server (NTRS)

    Jentung, Ku; Ottenstein, Laura; Rogers, Paul; Cheung, Kwok; Obenschain, Arthur F. (Technical Monitor)

    2002-01-01

    This paper discusses the effect of the pressure drop on the operating temperature in a loop heat pipe (LHP). Because the evaporator and the compensation chamber (CC) both contain two-phase fluid, a thermodynamic constraint exists between the temperature difference and the pressure drop for these two components. As the pressure drop increases, so will the temperature difference. The temperature difference in turn causes an increase of the heat leak from the evaporator to the CC, resulting in a higher CC temperature. Furthermore, the heat leak strongly depends on the vapor void fraction inside the evaporator core. Tests were conducted by installing a valve on the vapor line so as to vary the pressure drop, and by charging the LHP with various amounts of fluid. Test results verify that the LHP operating temperature increases with an increasing differential pressure, and the temperature increase is a strong function of the fluid inventory in the loop.

  18. Response of driven sessile drops with contact-line dissipation.

    PubMed

    Bostwick, Joshua B; Steen, Paul H

    2016-11-04

    A partially-wetting sessile drop is driven by a sinusoidal pressure field that produces capillary waves on the liquid/gas interface. Response diagrams and phase shifts for the droplet, whose contact-line moves with contact-angle that is a smooth function of the contact line speed, are reported. Contact-line dissipation originating from the contact-line speed condition leads to damping for drops with finite contact-line mobility, even for inviscid fluids. The critical mobility and associated driving frequency to generate the largest contact-line dissipation is computed. Viscous dissipation is approximated using the irrotational flow and the critical Ohnesorge number bounding regions beyond which a given mode becomes over-damped is computed. Regions of modal coexistence where two modes can be simultaneously excited by a single forcing frequency are identified. Predictions compare favorably to related experiments on vibrated drops.

  19. Drop stability in wind: theory

    NASA Astrophysics Data System (ADS)

    Lee, Sungyon

    2015-11-01

    Water drops may remain pinned on a solid substrate against external forcing due to contact angle hysteresis. Schmucker and White investigated this phenomenon experimentally in a high Reynolds number regime, by measuring the critical wind velocity at which partially wetting water drops depin inside a wind tunnel. Due to the unsteady turbulent boundary layer, droplets are observed to undergo vortex-shedding induced oscillations. By contrast, the overall elongation of the drop prior to depinning occurs on a much slower timescale with self-similar droplet shapes at the onset. Based on these observations, a simple, quasi-static model of depinning droplet is developed by implementing the phenomenological description of the boundary layer. The resultant model successfully captures the critical onset of droplet motion and is the first of on-going studies that connect the classical boundary layer theory with droplet dynamics.

  20. Isoelectric focusing in a drop.

    PubMed

    Weiss, Noah G; Hayes, Mark A; Garcia, Antonio A; Ansari, Rafat R

    2011-01-04

    A novel approach to molecular separations is investigated using a technique termed droplet-based isoelectric focusing. Drops are manipulated discretely on a superhydrophobic surface, subjected to low voltages for isoelectric focusing, and split-resulting in a preparative separation. A universal indicator dye demonstrates the generation of stable, reversible pH gradients (3-10) in ampholyte buffers, and these gradients lead to protein focusing within the drop length. Focusing was visually characterized, spectroscopically verified, and assessed quantitatively by noninvasive light scattering measurements. It was found to correlate with a quantitative model based on 1D steady-state theory. This work illustrates that molecular separations can be deployed within a single open drop, and the differential fractions can be separated into new discrete liquid elements.

  1. Serious Fun: Using Toys to Demonstrate Fluid Mechanics Principles

    ERIC Educational Resources Information Center

    Saviz, Camilla M.; Shakerin, Said

    2014-01-01

    Many students have owned or seen fluids toys in which two immiscible fluids within a closed container can be tilted to generate waves. These types of inexpensive and readily available toys are fun to play with, but they are also useful for provoking student learning about fluid properties or complex fluid behavior, including drop formation and…

  2. Numerical simulation of drop and bubble dynamics with soluble surfactant

    NASA Astrophysics Data System (ADS)

    Wang, Qiming; Siegel, Michael; Booty, Michael R.

    2014-05-01

    Numerical computations are presented to study the effect of soluble surfactant on the deformation and breakup of an axisymmetric drop or bubble stretched by an imposed linear strain flow in a viscous fluid. At the high values of bulk Peclet number Pe in typical fluid-surfactant systems, there is a thin transition layer near the interface in which the surfactant concentration varies rapidly. The large surfactant gradients are resolved using a fast and accurate "hybrid" numerical method that incorporates a separate, singular perturbation analysis of the dynamics in the transition layer into a full numerical solution of the free boundary problem. The method is used to investigate the dependence of drop deformation on parameters that characterize surfactant solubility. We also compute resolved examples of tipstreaming, and investigate its dependence on parameters such as flow rate and bulk surfactant concentration.

  3. Interfacial Instabilities in Evaporating Drops

    NASA Astrophysics Data System (ADS)

    Moffat, Ross; Sefiane, Khellil; Matar, Omar

    2007-11-01

    We study the effect of substrate thermal properties on the evaporation of sessile drops of various liquids. An infra-red imaging technique was used to record the interfacial temperature. This technique illustrates the non-uniformity in interfacial temperature distribution that characterises the evaporation process. Our results also demonstrate that the evaporation of methanol droplets is accompanied by the formation of wave-trains in the interfacial temperature field; similar patterns, however, were not observed in the case of water droplets. More complex patterns are observed for FC-72 refrigerant drops. The effect of substrate thermal conductivity on the structure of the complex pattern formation is also elucidated.

  4. Experiments of drops impacting a smooth solid surface: a model of the critical impact speed for drop splashing.

    PubMed

    Riboux, Guillaume; Gordillo, José Manuel

    2014-07-11

    Making use of experimental and theoretical considerations, in this Letter we deduce a criterion to determine the critical velocity for which a drop impacting a smooth dry surface either spreads over the substrate or disintegrates into smaller droplets. The derived equation, which expresses the splash threshold velocity as a function of the material properties of the two fluids involved, the drop radius, and the mean free path of the molecules composing the surrounding gaseous atmosphere, has been thoroughly validated experimentally at normal atmospheric conditions using eight different liquids with viscosities ranging from μ=3×10(-4) to μ=10(-2)  Pa s, and interfacial tension coefficients varying between σ=17 and σ=72  mN m(-1). Our predictions are also in fair agreement with the measured critical speed of drops impacting in different gases at reduced pressures given by Xu et al. [Phys. Rev. Lett. 94, 184505 (2005).

  5. Stability of a compound sessile drop at the axisymmetric configuration.

    PubMed

    Zhang, Ying; Chatain, Dominique; Anna, Shelley L; Garoff, Stephen

    2016-01-15

    The equilibrium configuration of compound sessile drops has been calculated previously in the absence of gravity. Using the Laplace equations, we establish seven dimensionless parameters describing the axisymmetric configuration in the presence of gravity. The equilibrium axisymmetric configuration can be either stable or unstable depending on the fluid properties. A stability criterion is established by calculating forces on a perturbed Laplacian shape. In the zero Bond number limit, the stability criterion depends on the density ratio, two ratios of interfacial tensions, the volume ratio of the two drops, and the contact angle. We use Surface Evolver to examine the stability of compound sessile drops at small and large Bond numbers and compare with the zero Bond number approximation. Experimentally, we realize a stable axisymmetric compound sessile drop in air, where the buoyancy force exerted by the air is negligible. Finally, using a pair of fluids in which the density ratio can be tuned nearly independently of the interfacial tensions, the stability transition is verified for the axisymmetric configuration. Even though the perturbations are different for the theory, simulations and experiments, both simulations and experiments agree closely with the zero Bond number approximation, exhibiting a small discrepancy at large Bond number.

  6. Regimes in secondary atomization of shear thinning inelastic drops

    NASA Astrophysics Data System (ADS)

    Kulkarni, Varun; Rocha, Jonathan; Sojka, Paul

    2016-11-01

    Secondary atomization plays a key role in the determining the eventual drop size distribution of a spray from an injector. Studies until recently have primarily focused on drops made of Newtonian or viscoelastic fluids. However, little is known about the breakup of single drop made of a shear thinning fluid subjected to cross flow of air. In this study we attempt to classify, experimentally, the regimes of breakup and morphology of an inelastic, shear thinning drop. Six different CMC water/glycerine based solutions are tested. The morphological patterns are classified on a We/Oh2 - 1/Oh2 plot using the zero shear rate viscosity where We denotes the Weber number and Oh is the Ohnesorge number. The regime boundaries for the various breakup patterns are juxtaposed with their Newtonian counterparts to highlight the differences. We observe a dependence on the Carreau number, Cu and power law index, n. The results converge to the Newtonian limit for particular cases of Cu and n.

  7. Two-Dimensional, High Flow, Precisely Controlled Monodisperse Drop Source

    DTIC Science & Technology

    1993-03-15

    on the energy in the acoustic drive to grow large enough to form a spray. If the acoustic signal is removed, the atomization ceases. Since these...circular jet, wherein the perturbations have a wavelength longer than the circumference of the jet. The applied perturbations grow , due to an input of en...Salt-Shaker Drop Generator because of the similarity to the hand-powered device used to eject salt crystals from a nozzle array. METAL ALTERNATE FLUID

  8. Compound pendant drop tensiometry for interfacial tension measurement at zero bond number.

    PubMed

    Neeson, Michael J; Chan, Derek Y C; Tabor, Rico F

    2014-12-30

    A widely used method to determine the interfacial tension between fluids is to quantify the pendant drop shape that is determined by gravity and interfacial tension forces. Failure of this method for small drops or small fluid density differences is a critical limitation in microfluidic applications and when only small fluid samples are available. By adding a small spherical particle to the interface to apply an axisymmetric deformation, both the particle density and the interfacial tension can be simultaneously and precisely determined, providing an accurate and elegant solution to a long-standing problem.

  9. 49 CFR 178.965 - Drop test.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Drop test. 178.965 Section 178.965 Transportation... Packagings § 178.965 Drop test. (a) General. The drop test must be conducted for the qualification of all...) Special preparation for the drop test. Large Packagings must be filled in accordance with § 178.960....

  10. 49 CFR 178.810 - Drop test.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Drop test. 178.810 Section 178.810 Transportation... Drop test. (a) General. The drop test must be conducted for the qualification of all IBC design types... the drop test. (1) Metal, rigid plastic, and composite IBCs intended to contain solids must be...

  11. 49 CFR 178.1045 - Drop test.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Drop test. 178.1045 Section 178.1045... Containers § 178.1045 Drop test. (a) General. The drop test must be conducted for the qualification of all... subpart. (b) Special preparation for the drop test. Flexible Bulk Containers must be filled to...

  12. 49 CFR 178.603 - Drop test.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Drop test. 178.603 Section 178.603 Transportation... Packagings and Packages § 178.603 Drop test. (a) General. The drop test must be conducted for the... than flat drops, the center of gravity of the test packaging must be vertically over the point...

  13. Computations of the deformation and solidifcation of impinging liquid metal drops

    NASA Astrophysics Data System (ADS)

    Che, Judy; Tryggvason, Gretar; Ceccio, Steven

    1997-11-01

    The solidification of individual liquid metal drops impacting a cold wall, as well as the deposition of subsequent drops characterized by drop remelt, coalescence, and solidification, are simulated numerically. The numerical method fully couples fluid flow and heat transfer and is based on a single set of conservation equations written for all phases, allowing for arbitrary changes in material properties. Solidification is modeled as a stable, planar solid-liquid interface, which is valid for both pure and eutectic systems with no initial thermal undercooling. Using this technique, towers have been built by depositing drops on top of one another. Low Weber number simulations produce short, squat towers, while high Weber number cases generate tall, slender towers. Within a tower, each drop takes on a final shape based on the Peclet number and the non- dimensional freezing temperature. In some high Peclet number cases, divots freeze onto a drop's surface forming a pore at the axis of the tower. Supported by NASA.

  14. Multimode dynamics of a liquid drop over an inclined surface with a wettability gradient.

    PubMed

    Das, A K; Das, P K

    2010-06-15

    A liquid drop placed over a solid surface with a wettability gradient self-propels to minimize its surface energy. It can also climb an inclined plane if the applied gradient strength is high enough. We investigate the motion of liquid drops over an inclined gradient surface using a unique 3D computational technique. The technique combines diffuse interface in a smoothed particle hydrodynamics simulation to study the internal fluid structure and the contact line dynamics. Simulation results reveal that drop motion is dependent on its volume, surface inclination, and the strength of the wettability gradient. It has been demonstrated that, depending on these parameters, a drop can experience upward or downward motion or can remain stationary on the inclined plane. Finally, drop mobility maps which give an idea about the regimes of uphill and downhill movement of a drop over gradient surfaces have been proposed.

  15. Simulation of drop movement over an inclined surface using smoothed particle hydrodynamics.

    PubMed

    Das, Arup K; Das, Prasanta K

    2009-10-06

    Smoothed particle hydrodynamics (SPH) is used to numerically simulate the movement of drops down an inclined plane. Diffuse interfaces have been assumed for tracking the motion of the contact line. The asymmetric shape of the three-dimensional drop and the variation of contact angle along its periphery can be calculated using the simulation. During the motion of a liquid drop down an inclined plane, an internal circulation of liquid particles is observed due to gravitational pull which causes periodic change in the drop shape. The critical angle of inclination required for the inception of drop motion is also evaluated for different fluids as a function of drop volume. The numerical predictions exhibit a good agreement with the published experimental results.

  16. Automated electric charge measurements of fluid microdrops using the Millikan method

    NASA Astrophysics Data System (ADS)

    Lee, Eric R.; Halyo, Valerie; Lee, Irwin T.; Perl, Martin L.

    2004-10-01

    Automated measurements of the electric charge of fluid microdrops precise to up to 0.016 of an electron charge have been made using machine-vision systems to observe the motion of fluid microdrops in air under the influence of an oscillating electric field. The fluid drop diameters have ranged from 7 µm to 25 µm with smaller diameter drops being measured to higher precision. The experimental runs performed for the purpose of attempting to find isolated fractionally electrically charged particles have measured the charges of tens of millions of fluid microdrops using piezoelectrically driven drop-on-demand inkjet-like droplet ejectors as fluid drop sources.

  17. Dispersion in Spherical Water Drops.

    ERIC Educational Resources Information Center

    Eliason, John C., Jr.

    1989-01-01

    Discusses a laboratory exercise simulating the paths of light rays through spherical water drops by applying principles of ray optics and geometry. Describes four parts: determining the output angles, computer simulation, explorations, model testing, and solutions. Provides a computer program and some diagrams. (YP)

  18. Getting the Drop on Sediment

    ERIC Educational Resources Information Center

    Galindez, Peter

    1977-01-01

    In this exercise, students examine Aristotle's weight hypothesis by testing variously shaped marble chips. These chips are weighed and dropped down a water tube. Average fall times and weights are recorded and graphed. Students are asked to apply this information to rock and soil deposition by streams. (MA)

  19. More investigations in capillary fluidics using a drop tower

    NASA Astrophysics Data System (ADS)

    Wollman, Andrew; Weislogel, Mark; Wiles, Brently; Pettit, Donald; Snyder, Trevor

    2016-04-01

    A variety of contemplative demonstrations concerning intermediate-to-large length scale capillary fluidic phenomena were made possible by the brief weightless environment of a drop tower (Wollman and Weislogel in Exp Fluids 54(4):1, 2013). In that work, capillarity-driven flows leading to unique spontaneous droplet ejections, bubble ingestions, and multiphase flows were introduced and discussed. Such efforts are continued herein. The spontaneous droplet ejection phenomena (auto-ejection) is reviewed and demonstrated on earth as well as aboard the International Space Station. This technique is then applied to novel low-g droplet combustion where soot tube structures are created in the wakes of burning drops. A variety of new tests are presented that routinely demonstrate `puddle jumping,' a process defined as the spontaneous recoil and ejection of large liquid drops from hydrophobic surfaces following the step reduction in `gravity' characteristic of most drop towers. The inverse problem of `bubble jumping' is also demonstrated for the case of hydrophilic surfaces. A variety of puddle jump demonstrations are presented in summary as a means of suggesting the further exploitation of drop towers to study such large length scale capillary phenomena.

  20. Liquid drops and surface tension with smoothed particle applied mechanics

    NASA Astrophysics Data System (ADS)

    Nugent, S.; Posch, H. A.

    2000-10-01

    Smoothed particle applied mechanics (SPAM), also referred to as smoothed particle hydrodynamics, is a Lagrangian particle method for the simulation of continuous flows. Here we apply it to the formation of a liquid drop, surrounded by its vapor, for a van der Waals (vdW) fluid in two dimensions. The cohesive pressure of the vdW equation of state gives rise to an attractive, central force between the particles with an interaction range which is assumed to exceed the interaction range of all the other smoothed forces in the SPAM equations of motion. With this assumption, stable drops are formed, and the vdW phase diagram is well reproduced by the simulations. Below the critical temperature, the surface tension for equilibrated drops may be computed from the pressure excess in their centers. It agrees very well with the surface tension independently determined from the vibrational frequency of weakly excited drops. We also study strongly deformed drops performing large-amplitude oscillations, which are reminiscent of the oscillations of a large ball of water under microgravity conditions. In an appendix we comment on the limitations of SPAM by studying the violation of angular momentum conservation, which is a consequence of noncentral forces contributed by the full Newtonian viscous stress tensor.

  1. Rayleigh Taylor instability of viscoelastic drops at high Weber numbers

    NASA Astrophysics Data System (ADS)

    Joseph, D. D.; Beavers, G. S.; Funada, T.

    2002-02-01

    Movies of the breakup of viscous and viscoelastic drops in the high-speed airstream behind a shock wave in a shock tube have been reported by Joseph, Belanger & Beavers (1999). They performed a Rayleigh Taylor stability analysis for the initial breakup of a drop of Newtonian liquid and found that the most unstable Rayleigh Taylor wave fits nearly perfectly with waves measured on enhanced images of drops from the movies, but the effects of viscosity cannot be neglected. Here we construct a Rayleigh Taylor stability analysis for an Oldroyd-B fluid using measured data for acceleration, density, viscosity and relaxation time [lambda]1. The most unstable wave is a sensitive function of the retardation time [lambda]2 which fits experiments when [lambda]2/[lambda]1 = O(10-3). The growth rates for the most unstable wave are much larger than for the comparable viscous drop, which agrees with the surprising fact that the breakup times for viscoelastic drops are shorter. We construct an approximate analysis of Rayleigh Taylor instability based on viscoelastic potential flow which gives rise to nearly the same dispersion relation as the unapproximated analysis.

  2. Experimental study of drop impacts on soap films

    NASA Astrophysics Data System (ADS)

    Yawar, Ali; Basu, Saikat; Concha, Andres; Bandi, Mahesh

    2015-11-01

    Impinging drops on flowing and static soap films demonstrate at least three distinct types of impact regimes: (a) the drop bounces off the film surface, (b) it coalesces with the downstream flow for a moving film and for static films it gets assimilated within the film, and (c) it pierces through the film. The interaction presents a unique opportunity to explore the impact of a quasi one-dimensional object on a two-dimensional fluid, much like a comet impacting on a thin atmosphere. We present a detailed experimental study of droplet impacts on soap film flow, for a number of film inclination angles and falling heights of the drop. Imaging techniques employed include sodium lamp interferometry to measure film thickness fluctuations and particle tracking velocimetry to measure the velocity field. Film thickness measures approximately 10 microns and the drop diameter is 1 mm. We mostly observe the bouncing-off regime for smaller inclination angles. However, at higher impact angles, puncturing of the film becomes a more common occurrence. We show that when the drop bounces off the film, there is a momentum transfer leading to vortex dipole shedding, along with the generation of capillary waves; an impulsive regime that may share correspondence with the locomotion of water striders.

  3. Two touching spherical drops in a uniaxial compressional flow: The effect of interfacial slip

    NASA Astrophysics Data System (ADS)

    Goel, Sachin; Ramachandran, Arun

    2016-05-01

    This study presents a semi-analytical solution for the problem of two touching drops with slipping interfaces pushed against each other in a uniaxial compressional flow at low capillary and Reynolds numbers. The jump in the tangential velocity at the liquid-liquid interface is modeled using the Navier slip condition. Analytical solutions of the contact force, the drop-scale stresses, and the drop-scale pressure are provided as functions of the slip coefficient (" separators=" α ) , the viscosity ratio (" separators=" κ ) , and the drop size ratio (" separators=" k ) . Since unequal drop sizes are considered, two problems are solved in the tangent sphere co-ordinate system to determine the steady state position: a pair of touching drops with its contact point at the origin of an axisymmetric straining flow, and two touching drops placed in a uniform flow parallel to the axis of symmetry of the drops. A general observation is that the effect of slip is manifested most strongly for drops whose viscosity is much greater than the suspending fluid (" separators=" κ ≫ 1 ) . For highly viscous drops, the flow and stress fields transition from those corresponding to solid particles for ακ ≪ 1, to those for inviscid drops in the limit ακ ≫ 1. The analytical expressions provided here for the contact force and the stress distributions will serve to provide the restrictions that complete the definition of the lubrication flow problem in the thin film between the two colliding drops. While the contact force that drains fluid out of the thin film is relatively unaffected by slip, the tangential stress and pressure in the near-contact region are mitigated significantly for ακ ≫ 1. The latter is expected to assist coalescence at high capillary numbers.

  4. Insight into drop runback on hydrophilic to superhydrophobic surfaces by shearing airflow

    NASA Astrophysics Data System (ADS)

    Milne, Andrew J. B.; Amirfazli, Alidad

    2009-11-01

    Drop runback has many diverse applications including airfoil icing and fuel cell flooding. In this talk, we use surface science and fluid dynamics principles to explain incipient runback for a drop exposed to shearing airflow. Through experiments with single drops of water and hexadecane (0.5-100 μl) on PMMA, Teflon, and a superhydrophobic aluminum surface (SHS), wetting parameters such as surface tension, drop shape and contact angle are found to be major controllers of the minimum required air velocity for drop shedding. Exponential functions are proposed that relate air velocity to drop base length and projected area. By normalizing the results, the three water systems can be collapsed to a single curve that also explains results from other researchers, vastly increasing predictive power. SHS are seen to shed drops more easily compared to the other surfaces, with evidence that the drops roll along the surface instead of sliding. Using high speed video, oscillating drop shape and variation of contact angles are also analyzed as they change with air and drop speed.

  5. Stability of the Shape of Surfactant-Laden Drops Translating at Low Reynolds Number

    NASA Astrophysics Data System (ADS)

    Johnson, R. A.; Borhan, A.

    1998-11-01

    The effect of surfactant impurities on the shape evolution of initially nonspherical drops translating at low Reynolds number in an immiscible, otherwise quiescent fluid is studied numerically. The presence of surface-active impurities can significantly alter the rheological properties of the two-phase interface; surfactant convection and diffusion along the deforming interface, as well as the adsorption/desorption exchange between the interface and the bulk phases, can lead to variations of interfacial tension and a subsequent redistribution of surface pressure. A combination of the boundary-integral method and a finite difference scheme is used to solve the coupled fluid dynamics and surfactant transport problems, while the Frumkin adsorption framework is used to explore the effects of monolayer saturation and nonideal surfactant interactions. For small Bond numbers, it is shown that the drop achieves a spherical shape at steady-state, provided the initial deformation is not too large. For large initial deformations or large bond numbers, however, the drop does not reach a steady shape, and drop breakup occurs through either the formation of an elongated tail, or the development of a re-entrant cavity at the rear. These mechanisms of drop breakup are similar to those reported by Koh & Leal [Phys. Fluids A 1, 8 (1989)] for surfactant-free drops. The effect of surfactant impurities on the critical conditions for drop breakup will be discussed.

  6. Stability of the shape of a surfactant-laden drop translating at low Reynolds number

    NASA Astrophysics Data System (ADS)

    Johnson, Robert A.; Borhan, Ali

    2000-04-01

    We examine the effect of surfactants on the evolution of the shape of an initially nonspherical drop translating in an otherwise quiescent fluid at low Reynolds number. A combination of the boundary-integral method and a finite-difference scheme is used to solve the coupled fluid dynamics and surfactant transport problems, in conjunction with the Frumkin adsorption framework to account for the effects of monolayer saturation and nonideal surfactant interactions. For sufficiently small Bond numbers, the drop achieves a nonspherical steady shape. For large initial deformations or Bond numbers, however, the drop deforms continuously, and eventually breaks up through either the formation of an elongated tail or the development of a re-entrant cavity at the trailing end, similar to the mechanisms of drop breakup reported by Koh and Leal [Phys. Fluids A 1, 8 (1989)], and Pozrikidis [J. Fluid Mech. 210, 1 (1990)], for surfactant-free drops. Surfactants are found to have a destabilizing effect on the shape of translating drops. The destabilizing effect is mitigated by the presence of strongly-cohesive surfactant interactions, and by surfactant transport between the bulk and the interface.

  7. Surfactant Saturation of Drops in Microgravity by Terrestrial Simulation

    NASA Astrophysics Data System (ADS)

    Viviani, Antonio

    It is well known that diffusion plays an appreciable role in mass transfer only in the case of weak gravitational convection. However, even under such conditions the use of a surfactant as a dif-fusing substance essentially complicates the mass transfer processes. The appearance of gas or liquid inclusions in the surfactant solution causes the development of solutocapillary motion on their surface, which may become a generator of the large-scale flows in the surrounding liquid, especially in microgravity conditions. The paper presents the results of terrestrial simulation of such flows during saturation of the drop of weakly soluble fluid by a surfactant from its water solution forming a thin ( 1 ) horizontal layer. In our experiments, we used chlorobenzene and water as the basic fluids of the drop and the surrounding medium, respectively, and isopropyl alcohol -as a surfactant. The initial concentration 0 of the alcohol in the solution ranged from 5 to 50%. This lent specific feature to the saturation process, manifesting itself in the fact that at concentration higher than 25% a mutual dissolution of water and chlorobenzene began to increase. Visualization of flow structures and concentration fields showed that in laboratory conditions even at maximum suppression of the gravitational convection the saturation of the surfactant is a rather complicated process specified by the initial surfactant concentration in the solution and by the degree of the solution homogeneity. In the case of initially homoge-neous solution, a complicated character of mass transfer between the drop and the surrounding medium is evidently due to the small values of surfactant diffusion coefficients in basic flu-ids. Penetration of the surfactant into the drop leads to the formation of local inhomigeneities of the solution density at both sides of the interface and to the development of a slow three-dimensional flow of gravitational nature. An increase in the concentration gives rise to a

  8. Dynamics and shapes of ferrofluid drops under spatially uniform magnetic fields

    NASA Astrophysics Data System (ADS)

    Rowghanian, Payam; Serwane, Friedhelm; Kealhofer, David; Meinhart, Carl D.; Campas, Otger

    2016-11-01

    We study the shape and dynamics of a Newtonian ferrofluid drop immersed in a Newtonian and non-magnetic viscous fluid under the action of a uniform external magnetic field. We obtain the exact equilibrium drop shapes for arbitrary ferrofluids which describe unexplained previous experiments, characterize the extent of deviations of the exact shape from the commonly assumed ellipsoidal shape, and analyze the smoothness of highly curved tips in elongated drops. We present a comprehensive study of drop deformation for a Langevin ferrofluid. Using a computational scheme that allows fast and accurate simulations of ferrofluid drop dynamics, we show that the dynamics of drop deformation by an applied magnetic field is described up to a numerical factor by the same time scale as drop relaxation in the absence of any magnetic field. The numerical factor depends on the ratio of viscosities and the ratio of magnetic to capillary stresses, but is independent of the nature of the ferrofluid in most practical cases. Finally, we use the shape and dynamics of the magnetic drops to measure the rheology of complex fluids.

  9. Level Sensor for Cryogenic Fluids

    NASA Technical Reports Server (NTRS)

    Simmons, N. E.; Schroff, R. A.

    1983-01-01

    Hot wire sensor combined with voltage-comparator circuit monitors liquid level in cryogenic-fluid storage tanks. Sensor circuit adaptable to different liquids and sensors. Constant-current source drives current through sensing probe and fixed resistor. Voltage comparator circuits interpret voltage drops to tell whether probe is immersed in liquid and is current in probe.

  10. Drop impact on a fiber

    NASA Astrophysics Data System (ADS)

    Kim, Sung-Gil; Kim, Wonjung

    2016-04-01

    We present the results of a combined experimental and theoretical investigation of drop impact on a thin fiber. Using high-speed videography, we analyze the dynamics of droplet collision with a fiber. Based on the systematic experiments, we identify three outcomes of collision: capturing, single drop falling, and splitting. The outcomes are presented in a regime map, where the regime boundaries are explained through a scale analysis of forces. We also measure the liquid retention on the fiber after the droplet impact. By considering a liquid film on the fiber, we develop a mechanical model that predicts the residual water mass. Our model reveals that the residual mass depends critically on the fiber thickness and less on the impact speed. Our study can be extended to predicting the remaining droplet, critical problems in air filtration, water collection, and fiber coating.

  11. Dropped head syndrome in mitochondriopathy.

    PubMed

    Finsterer, J

    2004-11-01

    In a 63-year-old, 165-cm-tall woman with a history of repeated tick bites, dilative cardiomyopathy, osteoporosis, progressive head ptosis with neck stiffness and cervical pain developed. The family history was positive for thyroid dysfunction and neuromuscular disorders. Neurological examination revealed prominent forward head drop, weak anteflexion and retroflexion, nuchal rigidity, weakness of the shoulder girdle, cogwheel rigidity, and tetraspasticity. The lactate stress test was abnormal. Electromyograms of various muscles were myogenic. Muscle biopsy showed non-specific myogenic abnormalities and generally weak staining for cytochrome oxydase. Mitochondriopathy with multi-organ involvement was suspected. The response to anti-Parkinson medication was poor. In conclusion, dropped head syndrome (DHS) may be due to multi-organ mitochondriopathy, manifesting as Parkinsonism, tetraspasticity, dilative cardiomyopathy, osteoporosis, short stature, and myopathy. Anti-Parkinson medication is of limited effect.

  12. Reusable Material for Drop Tower

    DTIC Science & Technology

    2011-08-01

    UNCLASSIFIED: Distribution A. Approved for public release. REUSABLE MATERIAL FOR DROP TOWER A thesis written at TANK AUTOMOTIVE RESEARCH AND...ABSTRACT This thesis represents the capstone of my five years combined academic work at Kettering University and job experience at Tank Automotive ...NUMBER OF PAGES 57 19a. NAME OF RESPONSIBLE PERSON a. REPORT unclassified b. ABSTRACT unclassified c. THIS PAGE unclassified Standard Form

  13. Drop spreading with random viscosity

    PubMed Central

    2016-01-01

    We examine theoretically the spreading of a viscous liquid drop over a thin film of uniform thickness, assuming the liquid’s viscosity is regulated by the concentration of a solute that is carried passively by the spreading flow. The solute is assumed to be initially heterogeneous, having a spatial distribution with prescribed statistical features. To examine how this variability influences the drop’s motion, we investigate spreading in a planar geometry using lubrication theory, combining numerical simulations with asymptotic analysis. We assume diffusion is sufficient to suppress solute concentration gradients across but not along the film. The solute field beneath the bulk of the drop is stretched by the spreading flow, such that the initial solute concentration immediately behind the drop’s effective contact lines has a long-lived influence on the spreading rate. Over long periods, solute swept up from the precursor film accumulates in a short region behind the contact line, allowing patches of elevated viscosity within the precursor film to hinder spreading. A low-order model provides explicit predictions of the variances in spreading rate and drop location, which are validated against simulations. PMID:27843398

  14. How to freeze drop oscillations with powders

    NASA Astrophysics Data System (ADS)

    Marston, Jeremy; Zhu, Ying; Vakarelski, Ivan; Thoroddsen, Sigurdur

    2012-11-01

    We present experiments that show when a water drop impacts onto a bed of fine, hydrophobic powder, the final form of the drop can be very different from the spherical form with which it impacts. For all drop impact speeds, the drop rebounds due to the hydrophobic nature of the powder. However, we observe that above a critical impact speed, the drop undergoes a permanent deformation to a highly non-spherical shape with a complete coverage of powder, thus creating a deformed liquid marble. This powder coating acts to freeze the drop oscillations during rebound.

  15. Amniotic fluid

    MedlinePlus

    ... carefully. Removing a sample of the fluid through amniocentesis can provide information about the sex, health, and development of the fetus. Images Amniocentesis Amniotic fluid Polyhydramnios Amniotic fluid References Cunningham FG, ...

  16. Shaken not stirred —On internal flow patterns in oscillating sessile drops

    NASA Astrophysics Data System (ADS)

    Oh, J. M.; Legendre, D.; Mugele, F.

    2012-05-01

    We use numerical (volume of fluid) simulations to study the flow in an oscillating sessile drop immersed in an ambient immiscible fluid. The drop is excited by a sinusoidal variation of the contact angle at variable frequency. We identify the eigenfrequencies and eigenmodes of the drops and analyze the internal flow fields by following the trajectories of tracer particles. The flow fields display an oscillatory component as well as a time-averaged mean component. The latter is oriented upward along the surface of the drop from the contact line towards the apex and downward along the symmetry axis. It vanishes at high and low frequencies and displays a broad maximum around f=200-300 Hz. We show that the frequency dependence of the mean flow can be described in terms of Stokes drift driven by capillary waves that originate from the contact line, in agreement with recent experiments (Mugele F. et al., Lab Chip, 11 (2011) 2011).

  17. Analysis of Skylab fluid mechanics science demonstrations

    NASA Technical Reports Server (NTRS)

    Tegart, J. R.; Butz, J. R.

    1975-01-01

    The results of the data reduction and analysis of the Skylab fluid mechanics demonstrations are presented. All the fluid mechanics data available from the Skylab missions were identified and surveyed. The significant fluid mechanics phenomena were identified and reduced to measurable quantities wherever possible. Data correlations were performed using existing theories. Among the phenomena analyzed were: static low-g interface shapes, oscillation frequency and damping of a liquid drop, coalescence, rotating drop, liquid films and low-g ice melting. A survey of the possible applications of the results was made and future experiments are recommended.

  18. Progress on Concepts for Next-Generation Drop Tower Systems

    NASA Astrophysics Data System (ADS)

    Könemann, Thorben; Eigenbrod, Christian; Von Kampen, Peter; Laemmerzahl, Claus; Kaczmarczik, Ulrich

    2016-07-01

    The Center of Applied Space Technology and Microgravity (ZARM) founded by Prof. Dr.-Ing. Hans J. Rath in 1985 is part of the Department of Production Engineering at the University of Bremen, Germany. ZARM is mainly concentrated on fundamental investigations of gravitational and space-related phenomenas under conditions of weightlessness as well as questions and developments related to technologies for space. At ZARM about 100 scientists, engineers, and administrative staff as well as many students from different departments are employed. Today, ZARM is still one of the largest and most important research center for space sciences and technologies in Europe. With a height of 146 m the Bremen Drop Tower is the predominant facility of ZARM and also the only drop tower of its class in Europe. ZARM's ground-based laboratory offers the opportunity for daily short-term experiments under conditions of high-quality weightlessness at a level of 10-6 g (microgravity), which is one of the best achievable for ground-based flight opportunities. Scientists may choose up to three times a day between a single drop experiment with 4.74 s in simple free fall and an experiment in ZARM's worldwide unique catapult system with 9.3 s in weightlessness. Since the start of operation of the facility in 1990, over 7500 drops or catapult launches of more than 160 different experiment types from various scientific fields like fundamental physics, combustion, fluid dynamics, planetary formation / astrophysics, biology and materials sciences have been accomplished so far. In addition, more and more technology tests have been conducted under microgravity conditions at the Bremen Drop Tower in order to effectively prepare appropriate space missions in advance. In this paper we report on the progress on concepts for next-generation drop tower systems based on the GraviTower idea utilizing a guided electro-magnetic linear drive. Alternative concepts motivated by the scientific demand for higher

  19. Critical point wetting drop tower experiment

    NASA Technical Reports Server (NTRS)

    Kaukler, W. F.; Tcherneshoff, L. M.; Straits, S. R.

    1984-01-01

    Preliminary results for the Critical Point Wetting CPW Drop Tower Experiment are produced with immiscible systems. Much of the observed phenomena conformed to the anticipated behavior. More drops will be needed to test the CPW theory with these immiscible systems.

  20. The sessile drop method for immunohistochemical processing of unmounted sections of nervous tissue.

    PubMed

    Nadelhaft, I

    1984-12-01

    A novel method for the immunohistochemical processing of free-floating tissue sections is described. Sections are immersed within drops of solution arranged on a hydrophobic surface. The procedure consists of sequentially suctioning away one fluid drop and replacing it by another, while the section remains in place. The technique permits easy testing of different antiserum dilutions, comparisons among different immunohistochemical protocols, and comparison of different antisera on serial tissue sections. Comparison is made to processing mounted sections.

  1. Lateral vibration of a water drop and its motion on a vibrating surface.

    PubMed

    Dong, L; Chaudhury, A; Chaudhury, M K

    2006-11-01

    The resonant modes of sessile water drops on a hydrophobic substrate subjected to a small-amplitude lateral vibration are investigated using computational fluid dynamic (CFD) modeling. As the substrate is vibrated laterally, its momentum diffuses within the Stokes layer of the drop. Above the Stokes layer, the competition between the inertial and Laplace forces causes the formation of capillary waves on the surface of the drop. In the first part of this paper, the resonant states of water drops are illustrated by investigating the velocity profile and the hydrostatic force using a 3d simulation of the Navier-Stokes equation. The simulation also allows an estimation of the contact angle variation on both sides of the drop. In the second part of the paper, we investigate the effect of vibration on a water drop in contact with a vertical plate. Here, as the plate vibrates parallel to gravity, the contact line oscillates. Each oscillation is, however, rectified by hysteresis, thus inducing a ratcheting motion to the water droplet vertically downward. Maximum rectification occurs at the resonant states of the drop. A comparison between the frequency-dependent motion of these drops and the variation of contact angles on their both sides is made. The paper ends with a discussion on the movements of the drops on a horizontal hydrophobic surface subjected to an asymmetric vibration.

  2. Unusual Contact-Line Dynamics of Thick Films and Drops

    NASA Technical Reports Server (NTRS)

    Veretennikov, Igor; Agarwal, Abhishek; Indeikina, Alexandra; Chang, Hsueh-Chia

    1999-01-01

    We report several novel phenomena In contact-line and fingering dynamics of macroscopic spinning drops and gravity-driven films with dimensions larger than the capillary length. It is shown through experimental and theoretical analysis that such macroscopic films can exhibit various interfacial shapes, including multi valued ones, near the contact line due to a balance between the external body forces with capillarity. This rich variety of front shapes couples with the usual capillary, viscous, and intermolecular forces at the contact line to produce a rich and unexpected spectrum of contact-line dynamics. A single finger develops when part of the front becomes multivalued on a partially wetting macroscopic spinning drop in contrast to a different mechanism for microscopic drops of completely wetting fluids. Contrary to general expectation, we observe that, at high viscosity and low frequencies of rotation, the speed of a glycerine finger increases with increasing viscosity. Completely wetting Dow Corning 200 Fluid spreads faster over a dry inclined plane than a prewetted one. The presence of a thin prewetted film suppresses fingering both for gravity-driven flow and for spin coating. We analyze some of these unique phenomena in detail and offer qualitative physical explanations for the others.

  3. From surfactant adsorption kinetics to asymmetric nanomembrane mechanics: pendant drop experiments with subphase exchange.

    PubMed

    Ferri, James K; Kotsmar, Csaba; Miller, Reinhard

    2010-12-15

    Adsorption equilibrium is the state in which the chemical potential of each species in the interface and bulk is the same. Dynamic phenomena at fluid-fluid interfaces in the presence of surface active species are often probed by perturbing an interface or adjoining bulk phase from the equilibrium state. Many methods designed for studying kinetics at fluid-fluid interfaces focus on removing the system from equilibrium through dilation or compression of the interface. This modifies the surface excess concentration Γ(i) and allows the species distribution in the bulk C(i) to respond. There are only a few methods available for studying fluid-fluid interfaces which seek to control C(i) and allow the interface to respond with changes to Γ(i). Subphase exchange in pendant drops can be achieved by the injection and withdrawal of liquid into a drop at constant volumetric flow rate R(E) during which the interfacial area and drop volume V(D) are controlled to be approximately constant. This can be accomplished by forming a pendant drop at the tip of two coaxial capillary tubes. Although evolution of the subphase concentration C(i)(t) is dictated by extrinsic factors such as R(E) and V(D), complete subphase exchange can always be attained when a sufficient amount of liquid is used. This provides a means to tailor driving forces for adsorption and desorption in fluid-fluid systems and in some cases, fabricate interfacial materials of well-defined composition templated at these interfaces. The coaxial capillary pendant drop (CCPD) method opens a wide variety of experimental possibilities. Experiments and theoretical frameworks are reviewed for the study of surfactant exchange kinetics, macromolecular adsorption equilibrium and dynamics, as well as the fabrication of a wide range of soft surface materials and the characterization of their mechanics. Future directions for new experiments are also discussed.

  4. Dropped head syndrome. Three case-reports.

    PubMed

    Chaouat, D; Belange, G

    1999-01-01

    Dropped head syndrome is characterized by gradual forward sagging of the head due to weakness of the neck extensor muscles. We report three cases in elderly patients seen by rheumatologists at our institution. There was some evidence suggestive of a neurogenic process, whereas most reported cases of dropped head syndrome have been ascribed to myopathy. Dropped head syndrome can probably be produced by multiple causes. The close ties between dropped head syndrome and acquired camptocormia in adults are discussed.

  5. 49 CFR 572.102 - Drop test.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 7 2013-10-01 2013-10-01 false Drop test. 572.102 Section 572.102 Transportation..., DEPARTMENT OF TRANSPORTATION (CONTINUED) ANTHROPOMORPHIC TEST DEVICES Free Motion Headform § 572.102 Drop test. (a) When the headform is dropped from a height of 14.8 inches in accordance with paragraph (b)...

  6. 49 CFR 572.102 - Drop test.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 7 2011-10-01 2011-10-01 false Drop test. 572.102 Section 572.102 Transportation..., DEPARTMENT OF TRANSPORTATION (CONTINUED) ANTHROPOMORPHIC TEST DEVICES Free Motion Headform § 572.102 Drop test. (a) When the headform is dropped from a height of 14.8 inches in accordance with paragraph (b)...

  7. 49 CFR 572.102 - Drop test.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 7 2012-10-01 2012-10-01 false Drop test. 572.102 Section 572.102 Transportation..., DEPARTMENT OF TRANSPORTATION (CONTINUED) ANTHROPOMORPHIC TEST DEVICES Free Motion Headform § 572.102 Drop test. (a) When the headform is dropped from a height of 14.8 inches in accordance with paragraph (b)...

  8. Studies of complexity in fluid systems

    SciTech Connect

    Nagel, Sidney R.

    2000-06-12

    This is the final report of Grant DE-FG02-92ER25119, ''Studies of Complexity in Fluids'', we have investigated turbulence, flow in granular materials, singularities in evolution of fluid surfaces and selective withdrawal fluid flows. We have studied numerical methods for dealing with complex phenomena, and done simulations on the formation of river networks. We have also studied contact-line deposition that occurs in a drying drop.

  9. Measurement of surface and interfacial tension using pendant drop tensiometry.

    PubMed

    Berry, Joseph D; Neeson, Michael J; Dagastine, Raymond R; Chan, Derek Y C; Tabor, Rico F

    2015-09-15

    Pendant drop tensiometry offers a simple and elegant solution to determining surface and interfacial tension - a central parameter in many colloidal systems including emulsions, foams and wetting phenomena. The technique involves the acquisition of a silhouette of an axisymmetric fluid droplet, and iterative fitting of the Young-Laplace equation that balances gravitational deformation of the drop with the restorative interfacial tension. Since the advent of high-quality digital cameras and desktop computers, this process has been automated with high speed and precision. However, despite its beguiling simplicity, there are complications and limitations that accompany pendant drop tensiometry connected with both Bond number (the balance between interfacial tension and gravitational forces) and drop volume. Here, we discuss the process involved with going from a captured experimental image to a fitted interfacial tension value, highlighting pertinent features and limitations along the way. We introduce a new parameter, the Worthington number, Wo, to characterise the measurement precision. A fully functional, open-source acquisition and fitting software is provided to enable the reader to test and develop the technique further.

  10. Pumpless femtoliter drop-on-demand generation via satellite formation

    NASA Astrophysics Data System (ADS)

    Moon, Dustin; Lee, Dong Wook; Kang, In Seok

    2009-11-01

    Manipulation of discrete or digital droplets can be a key process in chemical, pharmaceutical process in micro scale. This paper provides a drop-on-demand generation method of such micro droplets. Many drop generation techniques have been developed, from flow focusing to electrospray, dispensing droplets into different phases. But due to relatively long microchannel length and the use of syringe pumps, these methods show some limitations for single drop generation at a wanted time. Satellites, an unwanted droplet generated from liquid bridge breakup, have rather stable size distribution resulting from its rapid formation mechanism. In this experimental work, satellites are formed between metallic capillaries of outer diameter 910, 460, 260 micron respectively, and inside a PDMS channel of 100 micron-depth. To form a liquid bridge and break it, capillaries can be moved, or pulsed electric field is applied to deform, elongate droplets, and to form an unstable liquid bridge, and break. Several fluids from DI water to PEG with and without polystyrene particles and E.Coli. were used to form satellite drops in air and in oil. Details of each behavior were captured using Photron PCI 1024X high speed camera and analyzed accordingly.

  11. Effects of auroral potential drops on plasma sheet dynamics

    NASA Astrophysics Data System (ADS)

    Xi, Sheng; Lotko, William; Zhang, Binzheng; Wiltberger, Michael; Lyon, John

    2016-11-01

    The reaction of the magnetosphere-ionosphere system to dynamic auroral potential drops is investigated using the Lyon-Fedder-Mobarry global model including, for the first time in a global simulation, the dissipative load of field-aligned potential drops in the low-altitude boundary condition. This extra load reduces the field-aligned current (j||) supplied by nightside reconnection dynamos. The system adapts by forcing the nightside X line closer to Earth, with a corresponding reduction in current lensing (j||/B = constant) at the ionosphere and additional contraction of the plasma sheet during substorm recovery and steady magnetospheric convection. For steady and moderate solar wind driving and with constant ionospheric conductance, the cross polar cap potential and hemispheric field-aligned current are lower by approximately the ratio of the peak field-aligned potential drop to the cross polar cap potential (10-15%) when potential drops are included. Hemispheric ionospheric Joule dissipation is less by 8%, while the area-integrated, average work done on the fluid by the reconnecting magnetotail field increases by 50% within |y| < 8 RE. Effects on the nightside plasma sheet include (1) an average X line 4 RE closer to Earth; (2) a 12% higher mean reconnection rate; and (3) dawn-dusk asymmetry in reconnection with a 17% higher rate in the premidnight sector.

  12. Fluid Mechanics of Taste

    NASA Astrophysics Data System (ADS)

    Noel, Alexis; Bhatia, Nitesh; Carter, Taren; Hu, David

    2015-11-01

    Saliva plays a key role in digestion, speech and tactile sensation. Lack of saliva, also known as dry mouth syndrome, increases risk of tooth decay and alters sense of taste; nearly 10% of the general population suffer from this syndrome. In this experimental study, we investigate the spreading of water drops on wet and dry tongues of pigs and cows. We find that drops spread faster on a wet tongue than a dry tongue. We rationalize the spreading rate by consideration of the tongue microstructure, such as as papillae, in promoting wicking. By investigating how tongue microstructure affects spreading of fluids, we may begin to how understand taste receptors are activated by eating and drinking.

  13. Rolling, sliding, and sticking of viscoplastic xanthan gum solution drops on a superhydrophobic surface

    NASA Astrophysics Data System (ADS)

    Kim, Minyoung; Lee, Eungjun; Kim, Do Hyun; Kwak, Rhokyun

    2016-11-01

    Dynamics of Newtonian fluid on a non-wettable substrate have been reported, but those of non-Newtonian fluid, especially of viscoplastic fluid showing a yield stress, are not fully characterized yet. Here, we investigate three distinct behaviors of a viscoplastic drop (xanthan gum solution) -rolling, sliding, and sticking- on an inclined superhydrophobic surface with various inclined angles (1-24 degree) and xanthan gum concentrations (0.25-1.5%). At a low concentration of xanthan gum (low yield stress) and/or a high inclined angle (high gravitational stress), the drop rolls down the surface as the gravitational stress exceeds the yield stress. As the concentration increases, and thus the yield stress exceeds the gravitational stress, the drop stays on the surface like a solid (sticking). However, if we adjust the gravitational stress to induce an adhesive failure between the xanthan gum drop and the surface (but still lower than the yield stress), the drop slides down the surface without rolling. To the best of our knowledge, this is the first direct characterization of the behavior of the viscoplastic drops on an inclined surface considering gravitational stress, yield stress, and adhesive failure.

  14. Drop Tower and Aircraft Capabilities

    NASA Technical Reports Server (NTRS)

    Urban, David L.

    2015-01-01

    This presentation is a brief introduction to existing capabilities in drop towers and low-gravity aircraft that will be presented as part of a Symposium: Microgravity Platforms Other Than the ISS, From Users to Suppliers which will be a half day program to bring together the international community of gravity-dependent scientists, program officials and technologists with the suppliers of low gravity platforms (current and future) to focus on the future requirements and use of platforms other than the International Space Station (ISS).

  15. Nor Any Drop To Drink

    NASA Astrophysics Data System (ADS)

    Lehr, Jay H.

    In Nor Any Drop To Drink author William Ashworth displays an exceptional grasp of the hydrologic cycle for one trained as a writer rather than as an earth scientist. Especially remarkable for a popular book is the no-nonsense manner in which he handles popular misconceptions about underground water. Authors of similar books generally mollify readers who hold fallacious, mysterious beliefs concerning groundwater flow. Ashworth gets their attention with the proverbial two-by-four between the eyes by declaring such fallacies to be 100% hogwash. He describes the groundwater system in an exceptionally accurate manner using precise analogies which benefit from his literary skill.

  16. Drag and drop display & builder

    SciTech Connect

    Bolshakov, Timofei B.; Petrov, Andrey D.; /Fermilab

    2007-12-01

    The Drag and Drop (DnD) Display & Builder is a component-oriented system that allows users to create visual representations of data received from data acquisition systems. It is an upgrade of a Synoptic Display mechanism used at Fermilab since 2002. Components can be graphically arranged and logically interconnected in the web-startable Project Builder. Projects can be either lightweight AJAX- and SVG-based web pages, or they can be started as Java applications. The new version was initiated as a response to discussions between the LHC Controls Group and Fermilab.

  17. Diffusiophoresis of a charged drop

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Shin, Sangwoo; Stone, Howard

    2016-11-01

    Diffusiophoresis describes the motion of colloids in an electrolytic solution under a concentration gradient. Most of the previous studies in diffusiophoresis have dealt with motion of rigid particles. Here, we study the diffusiophoresis of fluid particles analytically and experimentally. We obtain the analytical solution of the diffusiophoretic velocity of fluid particles by perturbation methods. Using charged oil droplets, we measure the droplet speed under solute concentration gradient and compare it with the analytical solution. Our findings have potential applications for oil recovery and drug delivery.

  18. Dynamics of squeezing fluids: Clapping wet hands

    NASA Astrophysics Data System (ADS)

    Gart, Sean; Chang, Brian; Slama, Brice; Goodnight, Randy; Um, Soong Ho; Jung, Sunghwan

    2013-08-01

    Droplets splash around when a fluid volume is quickly compressed. This phenomenon has been observed during common activities such as kids clapping with wet hands. The underlying mechanism involves a fluid volume being compressed vertically between two objects. This compression causes the fluid volume to be ejected radially and thereby generate fluid threads and droplets at a high speed. In this study, we designed and performed laboratory experiments to observe the process of thread and drop formation after a fluid is squeezed. A thicker rim at the outer edge forms and moves after the squeezing, and then becomes unstable and breaks into smaller drops. This process differs from previous well-known examples (i.e., transient crown splashes and continuous water bells) in aspects of transient fluid feeding, expanding rim dynamics, or sparsely distributed drops. We compared experimental measurements with theoretical models over three different stages; early squeezing, intermediate sheet-expansion, and later break-up of the liquid thread. In the earlier stage, the fluid is squeezed and its initial velocity is governed by the lubrication force. The outer rim of the liquid sheet forms curved trajectories due to gravity, inertia, drag, and surface tension. At the late stage, drop spacing set by the initial capillary instability does not change in the course of rim expansion, consequently final ejected droplets are very sparse compared to the size of the rim.

  19. Why a falling drop does not in general behave like a rising bubble

    PubMed Central

    Tripathi, Manoj Kumar; Sahu, Kirti Chandra; Govindarajan, Rama

    2014-01-01

    Is a settling drop equivalent to a rising bubble? The answer is known to be in general a no, but we show that when the density of the drop is less than 1.2 times that of the surrounding fluid, an equivalent bubble can be designed for small inertia and large surface tension. Hadamard's exact solution is shown to be better for this than making the Boussinesq approximation. Scaling relationships and numerical simulations show a bubble-drop equivalence for moderate inertia and surface tension, so long as the density ratio of the drop to its surroundings is close to unity. When this ratio is far from unity, the drop and the bubble are very different. We show that this is due to the tendency for vorticity to be concentrated in the lighter fluid, i.e. within the bubble but outside the drop. As the Galilei and Bond numbers are increased, a bubble displays underdamped shape oscillations, whereas beyond critical values of these numbers, over-damped behavior resulting in break-up takes place. The different circulation patterns result in thin and cup-like drops but bubbles thick at their base. These shapes are then prone to break-up at the sides and centre, respectively. PMID:24759766

  20. Small drops from large nozzles

    NASA Astrophysics Data System (ADS)

    Castrejon-Pita, Alfonso Arturo; Said Mohamed, Ahmed; Castrejon-Pita, Jose Rafael; Herrada, Miguel Angel

    2015-11-01

    We report experimental and numerical results of the generation of drops which are significantly smaller than the nozzle from which they are generated. The system consists of a cylindrical reservoir and two endplates. One plate is a thin metal sheet with a small orifice in its centre which acts as the nozzle. The other end consists of a piston which moves by the action of an elecromechanical actuator which in turn is driven by sine-shape pull-mode pulses. The meniscus (formed at the nozzle) is thus first overturned, forming a cavity. This cavity collapses and a thin and fast jet emerges from its centre. Under appropriate conditions the tip of this jet breaks up and produces a single diminutive drop. A good agreement between the experimental and numerical results was found. Also, a series of experiments were performed in order to study the effects that the pulse amplitude and width, together with variations in the liquid properties, have over the final size of the droplet. Based on these experiments, a predictive law for the droplet size has been derived. This work was funded by the Royal Society (University Research Fellowship and Research Grant), the John Fell Fund (Oxford University Press), the Ministry of Science and Education (DPI2013-46485 Spain), and the Junta de Andalucia (P08-TEP-31704128 Spain).

  1. Charged drop levitators and their applications

    NASA Technical Reports Server (NTRS)

    Rhim, W. K.; Chung, S. K.; Hyson, M. T.; Elleman, D. D.

    1987-01-01

    An account is given of the charged drop levitation characteristics of two different devices: (1) a feedback-controlled electrostatic levitator able to lift a several mm-diameter drop in 1g conditions, which is applicable to drop dynamics, crystal growth, and supercooling/solidification experiments; and (2) a linear quadrupole levitator, whose advantages are demonstrated in light of the results obtained for the charged drop instability experiment. The cause of the premature drop burstings observed is suggested to be an electron avalanche in the surrounding gaseous medium rather than the Rayleigh limit.

  2. Instability of the origami of a ferrofluid drop in a magnetic field.

    PubMed

    Jamin, Timothée; Py, Charlotte; Falcon, Eric

    2011-11-11

    Capillary origami is the wrapping of a usual fluid drop by a planar elastic membrane due to the interplay between capillary and elastic forces. Here, we use a drop of magnetic fluid whose shape is known to strongly depend on an applied magnetic field. We study the quasistatic and dynamical behaviors of such a magnetic capillary origami. We report the observation of an overturning instability that the origami undergoes at a critical magnetic field. This instability is triggered by an interplay between magnetic and gravitational energies in agreement with the theory presented here. Additional effects of elasticity and capillarity on this instability are also discussed.

  3. Contact angle of sessile drops in Lennard-Jones systems.

    PubMed

    Becker, Stefan; Urbassek, Herbert M; Horsch, Martin; Hasse, Hans

    2014-11-18

    Molecular dynamics simulations are used for studying the contact angle of nanoscale sessile drops on a planar solid wall in a system interacting via the truncated and shifted Lennard-Jones potential. The entire range between total wetting and dewetting is investigated by varying the solid-fluid dispersive interaction energy. The temperature is varied between the triple point and the critical temperature. A correlation is obtained for the contact angle in dependence of the temperature and the dispersive interaction energy. Size effects are studied by varying the number of fluid particles at otherwise constant conditions, using up to 150,000 particles. For particle numbers below 10,000, a decrease of the contact angle is found. This is attributed to a dependence of the solid-liquid surface tension on the droplet size. A convergence to a constant contact angle is observed for larger system sizes. The influence of the wall model is studied by varying the density of the wall. The effective solid-fluid dispersive interaction energy at a contact angle of θ = 90° is found to be independent of temperature and to decrease linearly with the solid density. A correlation is developed that describes the contact angle as a function of the dispersive interaction, the temperature, and the solid density. The density profile of the sessile drop and the surrounding vapor phase is described by a correlation combining a sigmoidal function and an oscillation term.

  4. Spatial Distribution of Large Cloud Drops

    NASA Technical Reports Server (NTRS)

    Marshak, Alexander; Knyazikhin, Yuri; Larsen, Michael; Wiscombe, Warren

    2004-01-01

    The analysis of aircraft measurements of individual drop sizes in clouds suggests that for sufficiently small volumes the mean number of cloud drops with a given radius is proportional to volume powered by a drop-size dependent exponent. For abundant small drops present, the exponent is 1 as assumed in conventional approach. However, for rarer large drops, the exponents fall below unity. We show striking examples of the spatial distribution of large cloud drops using models that simulate the observed power laws. In contrast to currently used models that assume homogeneity and therefore a Poisson distribution of cloud drops, these models show strong drop clustering, the more so the larger the drops. The degree of clustering is determined by the observed exponents. The strong clustering of large drops arises naturally from the observed power-law statistics. This clustering has vital consequences for rain physics explaining how rain can form so fast and also helps explain why remotely sensed cloud drop size is generally biased.

  5. Drop short control of electrode gap

    DOEpatents

    Fisher, Robert W.; Maroone, James P.; Tipping, Donald W.; Zanner, Frank J.

    1986-01-01

    During vacuum consumable arc remelting the electrode gap between a consumable electrode and a pool of molten metal is difficult to control. The present invention monitors drop shorts by detecting a decrease in the voltage between the consumable electrode and molten pool. The drop shorts and their associated voltage reductions occur as repetitive pulses which are closely correlated to the electrode gap. Thus, the method and apparatus of the present invention controls electrode gap based upon drop shorts detected from the monitored anode-cathode voltage. The number of drop shorts are accumulated, and each time the number of drop shorts reach a predetermined number, the average period between drop shorts is calculated from this predetermined number and the time in which this number is accumulated. This average drop short period is used in a drop short period electrode gap model which determines the actual electrode gap from the drop short. The actual electrode gap is then compared with a desired electrode gap which is selected to produce optimum operating conditions and the velocity of the consumable error is varied based upon the gap error. The consumable electrode is driven according to any prior art system at this velocity. In the preferred embodiment, a microprocessor system is utilized to perform the necessary calculations and further to monitor the duration of each drop short. If any drop short exceeds a preset duration period, the consumable electrode is rapidly retracted a predetermined distance to prevent bonding of the consumable electrode to the molten remelt.

  6. Footprint geometry and sessile drop resonance

    NASA Astrophysics Data System (ADS)

    Chang, Chun-Ti; Daniel, Susan; Steen, Paul H.

    2017-03-01

    In this work, we examine experimentally the resonance of a sessile drop with a square footprint (square drop) on a flat plate. Two families of modal behaviors are reported. One family is identified with the modes of sessile drops with circular footprints (circular drop), denoted as "spherical modes." The other family is associated with Faraday waves on a square liquid bath (square Faraday waves), denoted as "grid modes." The two families are distinguished based on their dispersion behaviors. By comparing the occurrence of the modes, we recognize spherical modes as the characteristic of sessile drops, and grid modes as the constrained response. Within a broader context, we further discuss the resonance modes of circular sessile drops and free spherical drops, and we recognize various modal behaviors as surface waves under different extents of constraint. From these, we conclude that sessile drops resonate according to how wave-number selection by footprint geometry and capillarity compete. For square drops, a dominant effect of footprint constraint leads to grid modes; otherwise, the drops exhibit spherical modes, the characteristic of sessile drops on flat plates.

  7. Large charged drop levitation against gravity

    NASA Technical Reports Server (NTRS)

    Rhim, Won-Kyu; Chung, Sang Kun; Hyson, Michael T.; Trinh, Eugene H.; Elleman, Daniel D.

    1987-01-01

    A hybrid electrostatic-acoustic levitator that can levitate and manipulate a large liquid drop in one gravity is presented. To the authors' knowledge, this is the first time such large drops (up to 4 mm in diameter in the case of water) have been levitated against 1-gravity. This makes possible, for the first time, many new experiments both in space and in ground-based laboratories, such as 1)supercooling and superheating, 2) containerless crystal growth from various salt solutions or melts, 3) drop dynamics of oscillating or rotating liquid drops, 4) drop evaporation and Rayleigh bursting, and 5) containerless material processing in space. The digital control system, liquid drop launch process, principles of electrode design, and design of a multipurpose room temperature levitation chamber are described. Preliminary results that demonstrate drop oscillation and rotation, and crystal growth from supersaturated salt solutions are presented.

  8. Interfacial tension measurements using MRI drop shape analysis.

    PubMed

    Hussain, R; Vogt, S J; Honari, A; Hollingsworth, K G; Sederman, A J; Mitchell, J; Johns, M L

    2014-02-18

    Accurate interfacial tension data for fluid systems such as hydrocarbons and water is essential to many applications such as reservoir oil and gas recovery predictions. Conventional interfacial tension measurement techniques typically use optical images to analyze droplet shapes but require that the continuous-phase fluid be optically transparent and that the fluids are not refractive index matched. Magnetic resonance images obtain contrast between fluids using other mechanisms such as magnetic relaxation weighting, so systems that are impossible to measure with optical methods may be analyzed. In this article, we present high-field (9.4 T) MRI images of various droplets analyzed with axisymmetric drop shape analysis. The resultant interfacial tension data show good agreement with literature data. The method is subsequently demonstrated using both opaque continuous phases and refractive-index-matched fluids. We conclude with a brief consideration of the potential to extrapolate the methodology to lower magnetic fields (0.3 T), featuring more accessible hardware; although droplet imaging is possible, resolution and stability do not currently permit accurate interfacial tension measurements.

  9. Dynamics of Aqueous Foam Drops

    NASA Technical Reports Server (NTRS)

    Akhatov, Iskander; McDaniel, J. Gregory; Holt, R. Glynn

    2001-01-01

    We develop a model for the nonlinear oscillations of spherical drops composed of aqueous foam. Beginning with a simple mixture law, and utilizing a mass-conserving bubble-in-cell scheme, we obtain a Rayleigh-Plesset-like equation for the dynamics of bubbles in a foam mixture. The dispersion relation for sound waves in a bubbly liquid is then coupled with a normal modes expansion to derive expressions for the frequencies of eigenmodal oscillations. These eigenmodal (breathing plus higher-order shape modes) frequencies are elicited as a function of the void fraction of the foam. A Mathieu-like equation is obtained for the dynamics of the higher-order shape modes and their parametric coupling to the breathing mode. The proposed model is used to explain recently obtained experimental data.

  10. Relaxation or breakup of a low-conductivity drop upon removal of a uniform dc electric field

    NASA Astrophysics Data System (ADS)

    Lanauze, Javier A.; Walker, Lynn M.; Khair, Aditya S.

    2016-07-01

    We quantify the dynamics of a prolate leaky dielectric drop upon removal of a uniform dc electric field. Experiments consisting of a castor oil drop suspended in silicone oil are compared against axisymmetric boundary integral computations that account for transient charging, or charge relaxation, of the interface. A temporal asymmetry between the drop deformation and relaxation processes is observed in the experiments and computations: The drop relaxes back to its spherical equilibrium shape faster than the time taken to achieve its steady-state deformation. During the deformation process, the electrical (Maxwell) stress deforms the drop along the direction of the applied field; it is counteracted by the capillary stress. During the relaxation process, i.e., after the field is removed, the electrical stress acts together with the capillary stress to quickly restore the drop back to equilibrium. This change in action of the electrical stress is responsible for the asymmetry between the drop deformation and relaxation. Notably, the electrical stress acts over the charge relaxation time scales of the fluids: Thus, counterintuitively, longer charging time scales yield faster drop relaxation. That is, the longer it takes for the interface to discharge, the faster the drop shape relaxes. We also present computational results for a drop that does not relax back to its initial spherical shape upon removal of the electric field; rather, the drop breaks up via an end-pinching mechanism.

  11. Puddle jumping: Spontaneous ejection of large liquid droplets from hydrophobic surfaces during drop tower tests

    NASA Astrophysics Data System (ADS)

    Attari, B.; Weislogel, M.; Wollman, A.; Chen, Y.; Snyder, T.

    2016-10-01

    Large droplets and puddles jump spontaneously from sufficiently hydrophobic surfaces during routine drop tower tests. The simple low-cost passive mechanism can in turn be used as an experimental device to investigate dynamic droplet phenomena for drops up to 104 times larger than their normal terrestrial counterparts. We provide and/or confirm quick and qualitative design guides for such "drop shooters" as employed in drop tower tests including relationships to predict droplet ejection durations and velocities as functions of drop volume, surface texture, surface contour, wettability pattern, and fluid properties including contact angle. The latter is determined via profile image comparisons with numerical equilibrium interface computations. Water drop volumes of 0.04-400 ml at ejection speeds of -0.007-0.12 m/s are demonstrated herein. A sample application of the drop jump method is made to the classic problem of low-gravity phase change heat transfer for large impinging drops. Many other candidate problems might be identified by the reader.

  12. A numerical study of drop-on-demand ink jets

    NASA Technical Reports Server (NTRS)

    Fromm, J.

    1982-01-01

    Ongoing work related to development and utilization of a numerical model for treating the fluid dynamics of ink jets is discussed. The model embodies the complete nonlinear, time dependent, axi-symmetric equations in finite difference form. The jet nozzle geometry with no-slip boundary conditions and the existence of a contact circle are included. The contact circle is allowed some freedom of movement, but wetting of exterior surfaces is not addressed. The principal objective in current numerical experiments is to determine what pressure history, in conjunction with surface forces, will lead to clean drop formation.

  13. Leidenfrost drops on a heated liquid pool

    NASA Astrophysics Data System (ADS)

    Maquet, L.; Sobac, B.; Darbois-Texier, B.; Duchesne, A.; Brandenbourger, M.; Rednikov, A.; Colinet, P.; Dorbolo, S.

    2016-09-01

    We show that a volatile liquid drop placed at the surface of a nonvolatile liquid pool warmer than the boiling point of the drop can be held in a Leidenfrost state even for vanishingly small superheats. Such an observation points to the importance of the substrate roughness, negligible in the case considered here, in determining the threshold Leidenfrost temperature. A theoretical model based on the one proposed by Sobac et al. [Phys. Rev. E 90, 053011 (2014), 10.1103/PhysRevE.90.053011] is developed in order to rationalize the experimental data. The shapes of the drop and of the liquid substrate are analyzed. The model notably provides scalings for the vapor film thickness profile. For small drops, these scalings appear to be identical to the case of a Leidenfrost drop on a solid substrate. For large drops, in contrast, they are different, and no evidence of chimney formation has been observed either experimentally or theoretically in the range of drop sizes considered in this study. Concerning the evaporation dynamics, the radius is shown to decrease linearly with time whatever the drop size, which differs from the case of a Leidenfrost drop on a solid substrate. For high superheats, the characteristic lifetime of the drops versus the superheat follows a scaling law that is derived from the model, but, at low superheats, it deviates from this scaling by rather saturating.

  14. Microgravity Experiment Programs for Students at the Bremen Drop Tower

    NASA Astrophysics Data System (ADS)

    Könemann, Thorben; Eigenbrod, Christian; Von Kampen, Peter; Laemmerzahl, Claus

    The Center of Applied Space Technology and Microgravity (ZARM) founded by Prof. Dr.-Ing. Hans J. Rath in 1985 is part of the Department of Production Engineering at the University of Bremen, Germany. ZARM established as a research center and currently headed by Prof. Dr. Claus Lämmerzahl is mainly concentrated on fundamental investigations of gravitational and space-related phenomenas under conditions of weightlessness as well as questions and developments related to technologies for space. At ZARM more than 70 scientists, engineers and administrative staff as well as many students from different departments are employed. Today, ZARM is still one of the largest and most important university institutes for space sciences and technologies in Europe as well as worldwide well known in the space community. With a height of 146 m the Bremen Drop Tower is the predominant facility of ZARM and also the only drop tower of its class in Europe. ZARM’s ground-based laboratory offers the opportunity for daily short-term experiments under conditions of high-quality weightlessness at a level of 10 (-6) g (microgravity). The provided quality is one of the purest for experiments under weightlessness worldwide achieved. The scientists may choose between a single drop experiment with 4.74 s in simple free fall and a catapult experiment with 9.3 s of weightlessness. Either in the drop or in the worldwide unique catapult operation routine the repetition rates of microgravity experiments at ZARM are always the same, generally up to 3 times per day. Since the start of operation of the facility in 1990, over 6750 launches of more than 160 different experiment types from various scientific fields like Fundamental Physics, Combustion, Fluid Dynamics, Planetary Formation / Astrophysics, Biology and Materials Sciences have been successfully accomplished so far. In our paper we will report and inform about microgravity experiment programs for students like „Drop Your Thesis!“ by ESA and

  15. Footprint Geometry and Sessile Drop Resonance

    NASA Astrophysics Data System (ADS)

    Chang, Chun-Ti; Daniel, Susan; Steen, Paul H.

    2016-11-01

    How does a sessile drop resonate if its footprint is square (square drop)? In this talk, we discuss the two distinct families of observed modes in our experiments. One family (spherical modes) is identified with the natural modes of capillary spherical caps, and the other (grid modes) with Faraday waves on a square bath (square Faraday waves). A square drop exhibits grid or spherical modes depending on its volume, and the two families of modes arise depending on how wavenumber selection of footprint geometry and capillarity compete. For square drops, a dominant effect of footprint constraint leads to grid modes which are constrained response; otherwise the drops exhibit spherical modes, the characteristic of sessile drops on flat plates. Chun-Ti Chang takes his new position at National Taiwan University on Aug. 15th, 2016. Until then, Chun-Ti Chang is affiliated with Technical University Dortmund, Germany.

  16. Trapping of drops by wetting defects

    PubMed Central

    't Mannetje, Dieter; Ghosh, Somnath; Lagraauw, Rudy; Otten, Simon; Pit, Arjen; Berendsen, Christian; Zeegers, Jos; van den Ende, Dirk; Mugele, Frieder

    2014-01-01

    Controlling the motion of drops on solid surfaces is crucial in many natural phenomena and technological processes including the collection and removal of rain drops, cleaning technology and heat exchangers. Topographic and chemical heterogeneities on solid surfaces give rise to pinning forces that can capture and steer drops in desired directions. Here we determine general physical conditions required for capturing sliding drops on an inclined plane that is equipped with electrically tunable wetting defects. By mapping the drop dynamics on the one-dimensional motion of a point mass, we demonstrate that the trapping process is controlled by two dimensionless parameters, the trapping strength measured in units of the driving force and the ratio between a viscous and an inertial time scale. Complementary experiments involving superhydrophobic surfaces with wetting defects demonstrate the general applicability of the concept. Moreover, we show that electrically tunable defects can be used to guide sliding drops along actively switchable tracks—with potential applications in microfluidics. PMID:24721935

  17. A perspective on the interfacial properties of nanoscopic liquid drops

    NASA Astrophysics Data System (ADS)

    Malijevský, Alexandr; Jackson, George

    2012-11-01

    century by Gibbs and then promoted by Tolman) with a microscopic DFT treatment allows for a direct and unambiguous description of the interfacial properties of drops of arbitrary size; DFT provides all of the bulk and surface characteristics of the system that are required to uniquely define its thermodynamic properties. In this vein, we propose a non-local mean-field DFT for Lennard-Jones (LJ) fluids to examine drops of varying size. A comparison of the predictions of our DFT with recent simulation data based on a second-order fluctuation analysis (Sampayo et al 2010 J. Chem. Phys. 132 141101) reveals the consistency of the two treatments. This observation highlights the significance of fluctuation effects in small drops, which give rise to additional entropic (thermal non-mechanical) contributions, in contrast to what one observes in the case of planar interfaces which are governed by the laws of mechanical equilibrium. A small negative Tolman length (which is found to be about a tenth of the molecular diameter) and a non-monotonic behaviour of the surface tension with the drop radius are predicted for the LJ fluid. Finally, the limits of the validity of the Tolman approach, the effect of the range of the intermolecular potential, and the behaviour of bubbles are briefly discussed.

  18. Fluid Mechanics.

    ERIC Educational Resources Information Center

    Drazin, Philip

    1987-01-01

    Outlines the contents of Volume II of "Principia" by Sir Isaac Newton. Reviews the contributions of subsequent scientists to the physics of fluid dynamics. Discusses the treatment of fluid mechanics in physics curricula. Highlights a few of the problems of modern research in fluid dynamics. Shows that problems still remain. (CW)

  19. An octahedron model for oscillating, bouncing drops

    NASA Astrophysics Data System (ADS)

    Blanchette, Francois

    2016-11-01

    We present a model for oscillating and bouncing liquid drops. The model uses 6 point masses distributed as the vertices of an octahedron, connected by linear springs. We derive the physically relevant choice of parameters and use this model to study drops bouncing on solid surfaces, as well as drops bouncing on a nearly inviscid liquid surfaces. The surfaces may be stationary of subject to forced oscillations.

  20. Triple-line behavior and wettability controlled by nanocoated substrates: influence on sessile drop evaporation.

    PubMed

    Sobac, B; Brutin, D

    2011-12-20

    In this article, we investigate the influence of the surface properties of substrates on the evaporation process. Using various nanocoatings, it is possible to modify the surface properties of substrates, such as the roughness and the surface energy, while maintaining constant thermal properties. Experiments are conducted under atmospheric conditions with five fluids (methanol, ethanol, propanol, toluene and water) and four coatings (PFC, PTFE, SiOC, and SiO(x)). The various combinations of these fluids and coatings allow for a wide range of drop evaporation properties to be studied: the dynamics of the triple line, the volatility of fluids, and a large range of wettabilities (from 17 to 135°). The experimental data are in very good quantitative agreement with existing models of quasi-steady, diffusion-driven evaporation. The experimental results show that the dynamics of the evaporative rate are proportional to the dynamics of the wetting radius. Thus, the models succeed in describing the evaporative dynamics throughout the evaporation process regardless of the behavior of the triple line. Moreover, the use of various liquids reveals the validity of the models regardless of their volatility. The results also confirm the recent finding of a universal relation for the time evolution of the drop mass, independent of the drop size and initial contact angle. Finally, this study highlights the separate and coupled roles of the triple line and the wettability on the sessile drop evaporation process. Data reveal that the more wet and pinned a drop, the shorter the evaporation time.

  1. Drop motion induced by vertical vibrations

    NASA Astrophysics Data System (ADS)

    Sartori, Paolo; Quagliati, Damiano; Varagnolo, Silvia; Pierno, Matteo; Mistura, Giampaolo; Magaletti, Francesco; Massimo Casciola, Carlo

    2015-11-01

    We have studied the motion of liquid drops on an inclined plate subject to vertical vibrations. The liquids comprised distilled water and different aqueous solutions of glycerol, ethanol and isopropanol spanning the range 1-39 mm2 s-1 in kinematic viscosities and 40-72 mN m-1 in surface tension. At sufficiently low oscillating amplitudes, the drops are always pinned to the surface. Vibrating the plate above a certain amplitude yields sliding of the drop. Further increasing the oscillating amplitude drives the drop upward against gravity. In the case of the most hydrophilic aqueous solutions, this motion is not observed and the drop only slides downward. Images taken with a fast camera show that the drop profile evolves in a different way during sliding and climbing. In particular, the climbing drop experiences a much bigger variation in its profile during an oscillating period. Complementary numerical simulations of 2D drops based on a diffuse interface approach confirm the experimental findings. The overall qualitative behavior is reproduced suggesting that the contact line pinning due to contact angle hysteresis is not necessary to explain the drop climbing.

  2. Dropped head presentation of mitochondrial myopathy.

    PubMed

    Rahim, Fazal; Gupta, Devanshi; Bertorini, Tulio E; Ledoux, Mark S

    2003-12-01

    Dropped head secondary to weakness of the neck extensors has been reported in a wide assortment of neuromuscular disorders. Infrequently, dropped head can be the first sign of disease. We describe two patients with dropped head as the presenting manifestation of mitochondrial myopathy. In both patients, serum lactate was elevated and muscle biopsy showed mitochondrial proliferation. Mitochondrial myopathy should be considered in the differential diagnosis of dropped head syndrome, particularly when other, more common causes such as myasthenia gravis, polymyositis, and amyotrophic lateral sclerosis have been excluded by appropriate laboratory and electrophysiological studies.

  3. Mass Remaining During Evaporation of Sessile Drop

    DTIC Science & Technology

    2008-09-01

    to> \\fyj Greek Symbols P Contact angle of sessile drop . n Droplet shape factor = h/d 6 Non-dimensional time = t/i V Air kinematic viscosity...factor n, = h / d (where h = maximum height of the drop ), which can also be directly related to the contact angle (P) of the drop , that is r| = (l-cos(P...three drop size (initial mass or volume) conditions with all other conditions the same. These runs have a constant contact angle , (3 = 16.5° ± 1.5

  4. Numerical simulations of vibrating sessile drop

    NASA Astrophysics Data System (ADS)

    Kahouadji, Lyes; Chergui, Jalel; Juric, Damir; Shin, Seungwon; Craster, Richard; Matar, Omar

    2016-11-01

    A vibrated drop constitutes a very rich physical system, blending both interfacial and volume phenomena. A remarkable experimental study was performed by M. Costalonga highlighting sessile drop motion subject to horizontal, vertical and oblique vibration. Several intriguing phenomena are observed such as drop walking and rapid droplet ejection. We perform three-dimensional direct numerical simulations of vibrating sessile drops where the phenomena described above are computed using the massively parallel multiphase code BLUE. EPSRC UK Programme Grant MEMPHIS (EP/K003976/1).

  5. Videographic Assessment of Glaucoma Drop Instillation

    PubMed Central

    Castillejos, Armando; Kahook, Malik; Jimenez-Roman, Jesus; Gonzalez-Salinas, Roberto

    2015-01-01

    ABSTRACT Purpose: To assess the effect of patient education on videotaped topical instillation of artificial tear drops on subsequent topical instillation. Materials and methods: Forty-five patients, who had been using glaucoma drops for at least 6 months and with a best-corrected visual acuity of 20/100 or better, were studied. The patients were asked to instill an artificial tear drop using their accustomed technique while being video recorded. The patients viewed the recordings, and the errors in their drop instillation method were pointed out. This was followed by an educational session on proper drop instillation technique. After 30 minutes, patients were videotaped instilling drops to ascertain the effect of the educational session. The variables compared were: number of drops instilled, number of drops reaching the ocular surface, and the number of times the tip of the medication bottle touched the eye or ocular adnexa. Results: Before the instruction session, patients squeezed an average of 1.5 ± 0.9 drops from the bottle, and the average number of drops reaching the conjunctival fornix was 0.9 ± 0.7. The tip of the bottle touched the ocular adnexa in 29/45 (64.4%) patients. After the education session, the patients squeezed an average of 1.2 ± 0.5 drops and an average of 1.2 ± 0.4 drops reached the conjunctival fornix. The tip of the bottle touched the ocular adnexa in 13/45 (28.9%) patients. With proper instructions, the percentage of patients that instilled just one drop on the eye increased from 66 to 82%. Conclusion: A single educational session on the proper use of topical drops improves the successful instillation of eye drops. However, it was not determined whether the patients will retain the improved instillation technique for long-term or if the intervention results in only a short-term improvement. How to cite this article: Lazcano-Gomez G, Castillejos A, Kahook M, Jimenez-Roman J, Gonzalez-Salinas R. Video-graphic Assessment of Glaucoma

  6. The sensitivity of drop motion due to the density and viscosity ratio

    NASA Astrophysics Data System (ADS)

    Ohta, Mitsuhiro; Yamaguchi, Shinya; Yoshida, Yutaka; Sussman, Mark

    2010-07-01

    The effect of the density and viscosity ratio on the motion of single drops rising in immiscible liquids is computationally investigated. The density and viscosity ratio play an important role in droplet morphology, unstable droplet behavior, and terminal droplet characteristics. The numerical method used in this investigation is a coupled level-set and volume-of-fluid method together with a sharp interface treatment for the interfacial jump conditions. The computations assume an axisymmetric geometry. Drop rise motion is highly dependent on the viscosity ratio. The results reported in this paper augment the information provided by the correlation table for bubble rise motion by Bhaga and Weber ["Bubbles in viscous liquids: Shapes, wakes and velocities," J. Fluid Mech. 105, 61 (1981)]. A drop-system with a large viscosity ratio is susceptible to exhibiting unstable motion in the large Eötvös number regions; an unstable drop can show complicated behavior with various breakup modes that are dependent on the Morton number. With regard to the effect of the density ratio, it is observed that the difference between a bubble and a drop with "equivalent" properties is not prominent except in the low Morton number regions. The results of investigating the effect of the density and viscosity ratio on drop motion indicate that the Morton number, Eötvös numbers, and viscosity ratio are the primary governing parameters and the density ratio is a secondary governing parameter.

  7. Fiber length and orientation prevent migration in fluid filters

    NASA Technical Reports Server (NTRS)

    Reiman, P. A.

    1966-01-01

    Stainless steel fiber web filter resists fiber migration which causes contamination of filtered fluids. This filter is capable of holding five times more particulate matter before arbitrary cutoff pressure drop and shows excellent retention in fuel flow at high rates.

  8. Correlation for Sessile Drop Evaporation

    NASA Astrophysics Data System (ADS)

    Kelly-Zion, Peter; Pursell, Christopher; Wassom, Gregory; Mandelkorn, Brenton; Nkinthorn, Chris

    2016-11-01

    To better understand how the evaporation of sessile drops and small puddles is controlled by the vapor phase transport mechanisms of mass diffusion and buoyancy-induced convection, the evaporation rates of eight liquids evaporating under a broad range of ambient conditions were correlated with physical and geometrical properties. Examination of the correlation provides valuable insight into how the roles of diffusive and convective transport change with physical and geometrical parameters. The correlation predicts measured evaporation rates to within a root-mean-square error of 7.3%. The correlation is composed of two terms, a term which provides the rate of evaporation under diffusion-only conditions, and a term which provides the influence of convection. This second term suggests the manner in which the processes of diffusion and convection are coupled. Both processes are dependent on the distribution of the vapor, through the molar concentration gradient for diffusion and through the mass density gradient for convection. The term representing the influence of convection is approximately inversely proportional to the square root of diffusivity, indicating the tendency of diffusive transport to reduce convection by making the vapor distribution more uniform. Financial support was provided by the ACS Petroleum Research Fund.

  9. Electrorheological fluids

    SciTech Connect

    Adolf, D.; Anderson, R.; Garino, T.; Halsey, T.C.; Hance, B.; Martin, J.E.; Odinek, J.

    1996-10-01

    An Electrorheological fluid is normally a low-viscosity colloidal suspension, but when an electric field is applied, the fluid undergoes a reversible transition to a solid, being able to support considerable stress without yield. Commercial possibilities for such fluids are enormous, including clutches, brakes, valves,shock absorbers, and stepper motors. However, performance of current fluids is inadequate for many proposed applications. Our goal was to engineer improved fluids by investigating the key technical issues underlying the solid-phase yield stress and the liquid to solid switching time. Our studies focused on field-induced interactions between colloidal particles that lead to solidification, the relation between fluid structure and performance (viscosity, yield stress), and the time evolution of structure in the fluid as the field is switched on or off.

  10. Surface modes of a sessile water drop: An optical tweezer based study

    NASA Astrophysics Data System (ADS)

    Ghosh, Shankar; Sharma, Prerna; Bhattacharya, S.

    2007-11-01

    A high-precision method to study the dynamics of two-fluid interfaces using an optical tweezer and a phase-sensitive detection technique are described. The disturbances set up at the interface are studied by analyzing the motion of an optically trapped particle in the bulk of the fluid, i.e., away from the interface. The usefulness of the technique is demonstrated for the well-known problem of a horizontally vibrated sessile liquid drop. The vibrational modes of the liquid drop excited by sinusoidally vibrating the support in a horizontal plane appear as resonances in the motion of the trapped particle. The nature of the resonance is studied in detail by measuring the real part, the imaginary part, and the phase response of the motion of the particle as a function of the "effective" size of the liquid drop. Excellent quantitative agreement with the theoretically predicted values of the eigenfrequencies and damping of the surface modes is obtained.

  11. Surface modes of a sessile water drop: an optical tweezer based study.

    PubMed

    Ghosh, Shankar; Sharma, Prerna; Bhattacharya, S

    2007-11-01

    A high-precision method to study the dynamics of two-fluid interfaces using an optical tweezer and a phase-sensitive detection technique are described. The disturbances set up at the interface are studied by analyzing the motion of an optically trapped particle in the bulk of the fluid, i.e., away from the interface. The usefulness of the technique is demonstrated for the well-known problem of a horizontally vibrated sessile liquid drop. The vibrational modes of the liquid drop excited by sinusoidally vibrating the support in a horizontal plane appear as resonances in the motion of the trapped particle. The nature of the resonance is studied in detail by measuring the real part, the imaginary part, and the phase response of the motion of the particle as a function of the "effective" size of the liquid drop. Excellent quantitative agreement with the theoretically predicted values of the eigenfrequencies and damping of the surface modes is obtained.

  12. Scaling During Drop Formation and Filament (Thread) Breakup

    NASA Astrophysics Data System (ADS)

    Wagoner, Brayden; Thete, Sumeet; Basaran, Osman

    2016-11-01

    Many free surface flows such as drop formation, filament (thread) breakup, and drop coalescence are important in applications as diverse as ink jet printing, atomization, and emulsion science and technology. A common feature of these flows is that they all exhibit finite time singularities. When a liquid filament undergoes capillary thinning and tends toward pinch-off, it is instructive to monitor how certain quantities, such as the thread's radius, vary with time remaining until the pinch-off singularity. Experimental determination of this so-called scaling behavior of thread radius and other quantities is important for testing scaling theories and the accuracy of numerical simulations of free surface flows. Conversely, the experimental measurements can be used to develop new theories when none are available. In this talk, we will present some novel ways of experimentally measuring scaling behaviors. The results will be highlighted in terms of experiments involving the formation and breakup of drops and filaments of (a) simple or pure Newtonian fluids and also (b) particle-laden liquids or suspensions containing non-Brownian particles.

  13. Impact and Penetration of Nanoparticle Suspension Drops into Porous Membranes

    NASA Astrophysics Data System (ADS)

    Sahu, Rakesh; Yarin, Alexander; Pourdeyhimi, Behnam

    2014-03-01

    The impacts and dynamic penetration of drops with suspended nanoparticles into porous membranes are studied experimentally and theoretically. This type of penetration is radically different from the wettability-driven imbibition. Two types of membranes are used in the experiments: (i) glass fiber filter membrane (wettable) and (ii) PTFE depth filter (non-wettable). The nanoparticle entrainment and deposition inside the membrane bulk is used to mostly visualize the ultimate penetration fronts of the carrier fluid by observing the cut cross-sections of the filter membranes, albeit also provides an insight into potentially new applications like circuit printing on nonwovens. The experimental results demonstrate that during the dynamic focusing responsible for water penetration into micro- and nanopores, water can penetrate into a non-wettable porous medium (PTFE). Water also penetrates by the same focusing mechanism into the wettable glass fiber membrane, where it additionally spreads on a much longer time scale due to the wettability-driven flow. A theory explaining dynamic penetration of liquid into porous medium after drop impact is proposed. It is used to explain and predict water penetration into the non-wettable media after drop impact, and the results are compared with the experimental data. The work was supported by the Nonwovens Cooperative Research Center (NCRC).

  14. Fluid dynamics on sieve trays

    SciTech Connect

    Hag, M.A.

    1982-08-01

    A study was conducted to investigate the effects of fluid properties on the hydrodynamics of sieve tray columns. The study showed that changes in liquid viscosity influenced froth height, while changes in liquid surface tension and density influenced total pressure drop across the trays. Liquid holdup was independent of these solution properties. The liquid systems used for the study were: water/glycerol for viscosity, water/ethanol for surface tension and methanol/chloroform for density.

  15. Spray formation with complex fluids

    NASA Astrophysics Data System (ADS)

    Lustig, S.; Rosen, M.

    2011-05-01

    Droplet formation through Faraday excitation has been tested in the low driving frequency limit. Kerosene was used to model liquid fuel with the addition of PIB in different proportions. All fluids were characterized in detail. The mechanisms of ejection were investigated to identify the relative influence of viscosity and surface tension. It was also possible to characterize the type of instability leading to the emission drop process.

  16. Effects of pressure drop and superficial velocity on the bubbling fluidized bed incinerator.

    PubMed

    Wang, Feng-Jehng; Chen, Suming; Lei, Perng-Kwei; Wu, Chung-Hsing

    2007-12-01

    Since performance and operational conditions, such as superficial velocity, pressure drop, particles viodage, and terminal velocity, are difficult to measure on an incinerator, this study used computational fluid dynamics (CFD) to determine numerical solutions. The effects of pressure drop and superficial velocity on a bubbling fluidized bed incinerator (BFBI) were evaluated. Analytical results indicated that simulation models were able to effectively predict the relationship between superficial velocity and pressure drop over bed height in the BFBI. Second, the models in BFBI were simplified to simulate scale-up beds without excessive computation time. Moreover, simulation and experimental results showed that minimum fluidization velocity of the BFBI must be controlled in at 0.188-3.684 m/s and pressure drop was mainly caused by bed particles.

  17. Heat transfer and pressure drop for air flow through enhanced passages. Final report

    SciTech Connect

    Obot, N.T.; Esen, E.B.

    1992-06-01

    An extensive experimental investigation was carried out to determine the pressure drop and heat transfer characteristics for laminar, transitional and turbulent flow of air through a smooth passage and twenty-three enhanced passages. The internal surfaces of all enhanced passages had spirally shaped geometries; these included fluted, finned/ribbed and indented surfaces. The Reynolds number (Re) was varied between 400 and 50000. The effect of heat transfer (wall cooling or fluid heating) on pressure drop is most significant within the transition region; the recorded pressure drop with heat transfer is much higher than that without heat transfer. The magnitude of this effect depends markedly on the average surface temperature and, to a lesser extent, on the geometric characteristics of the enhanced surfaces. When the pressure drop data are reduced as values of the Fanning friction factor(f), the results are about the same with and without heat transfer for turbulent flow, with moderate differences in the laminar and transition regions.

  18. Heat transfer and pressure drop for air flow through enhanced passages

    SciTech Connect

    Obot, N.T.; Esen, E.B.

    1992-06-01

    An extensive experimental investigation was carried out to determine the pressure drop and heat transfer characteristics for laminar, transitional and turbulent flow of air through a smooth passage and twenty-three enhanced passages. The internal surfaces of all enhanced passages had spirally shaped geometries; these included fluted, finned/ribbed and indented surfaces. The Reynolds number (Re) was varied between 400 and 50000. The effect of heat transfer (wall cooling or fluid heating) on pressure drop is most significant within the transition region; the recorded pressure drop with heat transfer is much higher than that without heat transfer. The magnitude of this effect depends markedly on the average surface temperature and, to a lesser extent, on the geometric characteristics of the enhanced surfaces. When the pressure drop data are reduced as values of the Fanning friction factor(f), the results are about the same with and without heat transfer for turbulent flow, with moderate differences in the laminar and transition regions.

  19. Deformation of a nearly hemispherical conducting drop due to an electric field: Theory and experiment

    NASA Astrophysics Data System (ADS)

    Corson, L. T.; Tsakonas, C.; Duffy, B. R.; Mottram, N. J.; Sage, I. C.; Brown, C. V.; Wilson, S. K.

    2014-12-01

    We consider, both theoretically and experimentally, the deformation due to an electric field of a pinned nearly hemispherical static sessile drop of an ionic fluid with a high conductivity resting on the lower substrate of a parallel-plate capacitor. Using both numerical and asymptotic approaches, we find solutions to the coupled electrostatic and augmented Young-Laplace equations which agree very well with the experimental results. Our asymptotic solution for the drop interface extends previous work in two ways, namely, to drops that have zero-field contact angles that are not exactly π/2 and to higher order in the applied electric field, and provides useful predictive equations for the changes in the height, contact angle, and pressure as functions of the zero-field contact angle, drop radius, surface tension, and applied electric field. The asymptotic solution requires some numerical computations, and so a surprisingly accurate approximate analytical asymptotic solution is also obtained.

  20. Two-dimensional variational vibroequilibria and Faraday's drops

    NASA Astrophysics Data System (ADS)

    Gavrilyuk, Ivan; Lukovsky, Ivan; Timokha, Alexander

    2004-11-01

    When contacting with acoustically-vibrated structures a fluid volume can take a [time-averaged] geometric shape differing from capillary equilibrium. In accordance with theorems by Beyer et al. (2001) this shape (vibroequilibrium) furnishes a local minimum of a [quasi-potential energy] functional. The variational problem contains five dimensionless parameters evaluating the fluid volume, the wave number of acoustic field in the fluid domain, the contact angle and two newly-introduced numbers (η1, η2) giving relationships between (surface tension, gravitation) and Kapitsa’s vibrational forces/energy. The paper focuses on negligible small wave numbers (incompressible fluid) and two-dimensional flows. Although the variational problem may in some isolated cases have analytical solutions, it requires in general numerical approaches. Numerical examples simulate experiments by Wolf (1969) and Ganiyev et al. (1977) on vibroequilibria in horizontally vibrating tanks. These show that there appear at least two types of stable vibroequilibria associated with symmetric (possible non-connected) and asymmetric surface shapes. The paper represents also numerical results on flattening and vibrostabilisation of a drop hanging beneath a vibrating plate (experiments by Faraday (1831)).

  1. Drop-on-demand for aqueous solutions of sodium alginate

    NASA Astrophysics Data System (ADS)

    Herran, C. Leigh; Coutris, Nicole

    2013-06-01

    Inkjet printing is a rapidly growing commercial process for applications that depend on precisely patterning micro-scale droplets. These applications increasingly require complex fluids, introducing viscoelastic properties which play an important role in droplet formation. The objective of this study is to determine how to obtain single, uniform and spherical ("successful") droplets from aqueous solutions of sodium alginate with a piezoelectric drop-on-demand printing method. In order to control the volume and velocities of droplets, the effect on the droplet formation of the characteristics of the waveform such as voltage amplitude and dwell time is studied. The results depend also on the fluid rheology. The viscosity of the chosen fluid is a function of the concentration, as the viscoelastic properties increase at higher concentration. In this paper, the droplet formation process is characterized in terms of both the waveform and the rheological properties of the solution. The characterization of the fluids and waveform will be pursued first and the droplet formation and its control will be studied. Finally, the results will be presented with a map in ranges of the Ohnesorge, Deborah and Weber numbers.

  2. Mixing in colliding, ultrasonically levitated drops.

    PubMed

    Chainani, Edward T; Choi, Woo-Hyuck; Ngo, Khanh T; Scheeline, Alexander

    2014-02-18

    Lab-in-a-drop, using ultrasonic levitation, has been actively investigated for the last two decades. Benefits include lack of contact between solutions and an apparatus and a lack of sample cross-contamination. Understanding and controlling mixing in the levitated drop is necessary for using an acoustically levitated drop as a microreactor, particularly for studying kinetics. A pulsed electrostatic delivery system enables addition and mixing of a desired-volume droplet with the levitated drop. Measurement of mixing kinetics is obtained by high-speed video monitoring of a titration reaction. Drop heterogeneity is visualized as 370 nl of 0.25 M KOH (pH: 13.4) was added to 3.7 μL of 0.058 M HCl (pH: 1.24). Spontaneous mixing time is about 2 s. Following droplet impact, the mixed drop orbits the levitator axis at about 5 Hz during homogenization. The video's green channel (maximum response near 540 nm) shows the color change due to phenolphthalein absorption. While mixing is at least an order of magnitude faster in the levitated drop compared with three-dimensional diffusion, modulation of the acoustic waveform near the surface acoustic wave resonance frequency of the levitated drop does not substantially reduce mixing time.

  3. Spatial Distribution of Large Cloud Drops

    NASA Technical Reports Server (NTRS)

    Marshak, A.; Knyazikhin, Y.; Larsen, M.; Wiscombe, W.

    2004-01-01

    By analyzing aircraft measurements of individual drop sizes in clouds, we have shown in a companion paper (Knyazikhin et al., 2004) that the probability of finding a drop of radius r at a linear scale l decreases as l(sup D(r)) where 0 less than or equal to D(r) less than or equal to 1. This paper shows striking examples of the spatial distribution of large cloud drops using models that simulate the observed power laws. In contrast to currently used models that assume homogeneity and therefore a Poisson distribution of cloud drops, these models show strong drop clustering, the more so the larger the drops. The degree of clustering is determined by the observed exponents D(r). The strong clustering of large drops arises naturally from the observed power-law statistics. This clustering has vital consequences for rain physics explaining how rain can form so fast. It also helps explain why remotely sensed cloud drop size is generally biased and why clouds absorb more sunlight than conventional radiative transfer models predict.

  4. Dropped head syndrome in Parkinson's disease.

    PubMed

    Kashihara, Kenichi; Ohno, Manabu; Tomita, Susumu

    2006-08-01

    We determined the frequency of dropped head syndrome in Parkinson's disease (PD) in Japan and evaluated its clinical correlates. A total of 252 consecutive patients with PD who visited our hospital were studied. Dropped head syndrome was found in 15 patients (6.0%) (3 men, 12 women; mean age at onset of PD, 62.8 +/- 11.5 years). The interval before emergence of dropped head after disease onset was 5.4 +/- 4.3 years (-0.5 to 15 years). The Hoehn-Yahr score at the on stage was 3.2 +/- 0.7; at the off stage 3.5 +/- 0.8. Of those 15 patients, 8 had major symptoms of rigidity and akinesia. In 2 patients, administration of a dopamine agonist appeared to evoke dropped head syndrome. An increase in and/or the addition of antiparkinsonian drugs alleviated head drop in 4 patients and reduced head drop in 7 patients. Any medication was not effective for 4 patients. Dropped head syndrome in PD is not rare in Japan. It is more often observed in women and is associated with patients who primarily suffer rigidity and akinesia. Dropped head syndrome in these patients appears to be produced by disproportionate tonus of the neck muscles. It is modulated by antiparkinsonian drugs and is considered to be a type of dystonia.

  5. Growth suppression caused by corticosteroid eye drops.

    PubMed

    Wolthers, Ole D

    2011-01-01

    Scarce data on systemic activity of corticosteroid eye drops are available in children. Two weeks treatment with fluorometholone eye drops in a case series of five children caused growth suppression detected by knemometry. The suppression had no impact on height growth during the following year.

  6. Drops and Bubble in Materials Science

    NASA Technical Reports Server (NTRS)

    Doremus, R. H.

    1982-01-01

    The formation of extended p-n junctions in semiconductors by drop migration, mechanisms and morphologies of migrating drops and bubbles in solids and nucleation and corrections to the Volmer-Weber equations are discussed. Bubble shrinkage in the processing of glass, the formation of glass microshells as laser-fusion targets, and radiation-induced voids in nuclear reactors were examined.

  7. Drop Ejection From an Oscillating Rod

    NASA Technical Reports Server (NTRS)

    Wilkes, E. D.; Basaran, O. A.

    1999-01-01

    The dynamics of a drop of a Newtonian liquid that is pendant from or sessile on a solid rod that is forced to undergo time-periodic oscillations along its axis is studied theoretically. The free boundary problem governing the time evolution of the shape of the drop and the flow field inside it is solved by a method of lines using a finite element algorithm incorporating an adaptive mesh. When the forcing amplitude is small, the drop approaches a limit cycle at large times and undergoes steady oscillations thereafter. However, drop breakup is the consequence if the forcing amplitude exceeds a critical value. Over a wide range of amplitudes above this critical value, drop ejection from the rod occurs during the second oscillation period from the commencement of rod motion. Remarkably, the shape of the interface at breakup and the volume of the primary drop formed are insensitive to changes in forcing amplitude. The interface shape at times close to and at breakup is a multi-valued function of distance measured along the rod axis and hence cannot be described by recently popularized one-dimensional approximations. The computations show that drop ejection occurs without the formation of a long neck. Therefore, this method of drop formation holds promise of preventing formation of undesirable satellite droplets.

  8. Aging, Terminal Decline, and Terminal Drop

    ERIC Educational Resources Information Center

    Palmore, Erdman; Cleveland, William

    1976-01-01

    Data from a 20-year longitudinal study of persons over 60 were analyzed by step-wise multiple regression to test for declines in function with age, for terminal decline (linear relationship to time before death), and for terminal drop (curvilinear relationship to time before death). There were no substantial terminal drop effects. (Author)

  9. 49 CFR 178.810 - Drop test.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... design types and performed periodically as specified in § 178.801(e) of this subpart. (b) Special...). (2) Drop tests are to be performed with the solid or liquid to be transported or with a non-hazardous... substituted non-hazardous material used in the drop test for liquids must be similar to the hazardous...

  10. Water drop friction on superhydrophobic surfaces.

    PubMed

    Olin, Pontus; Lindström, Stefan B; Pettersson, Torbjörn; Wågberg, Lars

    2013-07-23

    To investigate water drop friction on superhydrophobic surfaces, the motion of water drops on three different superhydrophobic surfaces has been studied by allowing drops to slide down an incline and capturing their motion using high-speed video. Two surfaces were prepared using crystallization of an alkyl ketene dimer (AKD) wax, and the third surface was the leaf of a Lotus (Nelumbo Nucifera). The acceleration of the water droplets on these superhydrophobic surfaces was measured as a function of droplet size and inclination of the surface. For small capillary numbers, we propose that the energy dissipation is dominated by intermittent pinning-depinning transitions at microscopic pinning sites along the trailing contact line of the drop, while at capillary numbers exceeding a critical value, energy dissipation is dominated by circulatory flow in the vicinity of the contacting disc between the droplet and the surface. By combining the results of the droplet acceleration with a theoretical model based on energy dissipation, we have introduced a material-specific coefficient called the superhydrophobic sliding resistance, b(sh). Once determined, this parameter is sufficient for predicting the motion of water drops on superhydrophobic surfaces of a general macroscopic topography. This theory also infers the existence of an equilibrium sliding angle, β(eq), at which the drop acceleration is zero. This angle is decreasing with the radius of the drop and is in quantitative agreement with the measured tilt angles required for a stationary drop to start sliding down an incline.

  11. 1D fluid model of the dielectric barrier discharge in chlorine

    NASA Astrophysics Data System (ADS)

    Avtaeva, Svetlana

    2016-09-01

    The 1D fluid model of the dielectric barrier discharge (DBD) in pure chlorine is developed. The discharge is excited in 8 mm gas gap between quartz dielectric layers of 2 mm thickness covered metallic electrodes. The source voltage US =U0 sin ωt with a frequency 100 kHz and amplitude 8 kV is applied to the electrodes. Chlorine pressure is varied from 15 to 100 Torr. At pressure of 15 Torr a breakdown appears with voltage drop across the discharge gap about 1 kV whereas at 100 Torr it appears with voltage drop about 2 kV. After the first current spike some lower current spikes are observes with chlorine pressure of 100 Torr and large in number current spikes of about identical magnitude are observed with the pressure of 15 Torr. The maximal current density at all pressures reaches about 4 mA/cm.2Total density of surface charge deposited on the electrodes during a half-cycle decreases with chlorine pressure because duration of the current spike discharge phase reduces with chlorine pressure. The average power density inputted in the discharge is 2.5-5.8 W/cm3 per a cycle. The Cl2 plasma is electronegative, the most abundant ions are Cl2+and Cl-. It is shown, that ions get about 95% of the discharge power as electrons get about 5% of the discharge power. 67-97% of the electron power is spending for dissociation and ionization of Cl2 molecules. Emission of Cl* atoms and Cl2*molecules is weak.

  12. A Novel Acousto-Electric Levitator for Studies of Drop and Particle Clusters and Arrays

    NASA Technical Reports Server (NTRS)

    Tian, Yuren; Apfel, Robert E.; Zheng, Yibing

    1999-01-01

    A novel and compact instrumentation for studying the behavior of drop sprays and of clusters of drops now permits fundamental research into the behavior of reacting and non-reacting fluid and solid species. The new capability is made possible by simultaneous acousto-electric levitation and charging of "seed" droplets (10-30 microns in diameter) which come together in 2-D clusters (with up to 300 droplets). These clusters are interesting in their own right because of their crystalline and quasi-crystalline forms, which depend on the acoustic and electric field parameters. By varying the electric and acoustic field intensities, one can cause a cluster of droplets to condense into larger drops (e.g. 50-300 microns) which, because of their charge, form uniformly spaced 2-D arrays of monodispersed drops (e.g. 30-40 array drops in preliminary experiments). One or more layers of these 2-D arrays can form in the acoustic standing wave. Such a configuration permits a wide range of fundamental studies of drop evaporation, combustion, and nucleation. The drops can be single or multicomponent. Therefore, fundamental materials studies can also be performed. Using this same Cluster and Array Generation (CAG) instrumentation, it has been also possible in preliminary experiments to demonstrate the clustering and arraying of solid particles, both coated with an electrically conducting layer and uncoated, and both charged and uncharged.

  13. Nonlinear electrohydrodynamics of leaky dielectric drops in the Quincke regime: Numerical simulations

    NASA Astrophysics Data System (ADS)

    Das, Debasish; Saintillan, David

    2015-11-01

    The deformation of leaky dielectric drops in a dielectric fluid medium when subject to a uniform electric field is a classic electrohydrodynamic phenomenon best described by the well-known Melcher-Taylor leaky dielectric model. In this work, we develop a three-dimensional boundary element method for the full leaky dielectric model to systematically study the deformation and dynamics of liquid drops in strong electric fields. We compare our results with existing numerical studies, most of which have been constrained to axisymmetric drops or have neglected interfacial charge convection by the flow. The leading effect of convection is to enhance deformation of prolate drops and suppress deformation of oblate drops, as previously observed in the axisymmetric case. The inclusion of charge convection also enables us to investigate the dynamics in the Quincke regime, in which experiments exhibit a symmetry-breaking bifurcation leading to a tank-treading regime. Our simulations confirm the existence of this bifurcation for highly viscous drops, and also reveal the development of sharp interfacial charge gradients driven by convection near the drop's equator. American Chemical Society, Petroleum Research Fund.

  14. New Method Developed to Measure Contact Angles of a Sessile Drop

    NASA Technical Reports Server (NTRS)

    Chao, David F.; Zhang, Nengli

    2002-01-01

    The spreading of an evaporating liquid on a solid surface occurs in many practical processes and is of importance in a number of practical situations such as painting, textile dyeing, coating, gluing, and thermal engineering. Typical processes involving heat transfer where the contact angle plays an important role are film cooling, boiling, and the heat transfer through heat pipes. The biological phenomenon of cell spreading also is analogous to a drop spreading (ref. 1). In the study of spreading, the dynamic contact angle describes the interfacial properties on solid substrates and, therefore, has been studied by physicists and fluid mechanics investigators. The dynamic contact angle of a spreading nonvolatile liquid drop provides a simple tool in the study of the free-boundary problem, but the study of the spreading of a volatile liquid drop is of more practical interest because the evaporation of common liquids is inevitable in practical processes. The most common method to measure the contact angle, the contact radius, and the height of a sessile drop on a solid surface is to view the drop from its edge through an optical microscope. However, this method gives only local information in the view direction. Zhang and Yang (ref. 2) developed a laser shadowgraphy method to investigate the evaporation of sessile drop on a glass plate. As described here, Zhang and Chao (refs. 3 and 4) improved the method and suggested a new optical arrangement to measure the dynamic contact angle and the instant evaporation rate of a sessile drop with much higher accuracy (less than 1 percent). With this method, any fluid motion in the evaporating drop can be visualized through shadowgraphy without using a tracer, which often affects the field under investigation.

  15. Axisymmetric Drop Shape Analysis (ADSA): An Outline.

    PubMed

    Saad, Sameh M I; Neumann, A Wilhelm

    2016-12-01

    Drop shape techniques for the measurement of interfacial tension are powerful, versatile and flexible. The shape of the drop/bubble depends on the balance between surface tension and external forces, e.g. gravity. This balance is reflected mathematically in the Laplace equation of capillarity. Axisymmetric Drop Shape Analysis (ADSA) is a commonly used drop shape technique. A streamlined version of the development of ADSA over the past several decades is presented to illustrate its validity and range of utility. Several configurations of interest will be considered and presented systematically. Shape and surface tension will be linked to a shape parameter based on proper concepts of differential geometry. The resulting shape parameter will be shown to allow determination of the range of applicability of such a drop shape method.

  16. Undercooling of acoustically levitated molten drops

    NASA Technical Reports Server (NTRS)

    Ohsaka, K.; Trinh, E. H.; Glicksman, M. E.

    1990-01-01

    It was observed that the acoustically levitated molten SCN (succinonitrile) drops can generally be undercooled to a degree where the impurities in the drop are responsible for the nucleation of the solid phase. However, it was also observed that ultrasound occasionally terminates undercooling of the levitated drops by initiating the nucleation of the solid at an undercooling level which is lower than that found for the nucleation catalyzed by the impurities in the drop. This premature nucleation can be explained by thermodynamic considerations which predict an increase in effective undercooling of the liquid upon the collapse of cavities. Pre-existing gas microbubbles which grow under the influence of ultrasound are suggested as the source of cavitation. The highly undercooled SCN drops can be utilized to measure the growth velocity of the solid in the deeply undercooled region including the hypercooled region.

  17. U. S. plastics demand drops sharply

    SciTech Connect

    Not Available

    1980-07-28

    According to the Society of the Plastics Industry, plastics demand dropped sharply in the U.S. during second-quarter 1980. U.S. exports of themoplastics are down slightly from year-ago levels, and PVC and low-density polyethylene (LDPE) exports are increasing strongly, but strong exports can not offset a weak domestic market. The weakness in domestic PVC sales is due mostly to large drops in contruction pipe (-49%) and automotive uses, its leading markets, in the last year. LDPE sales have dropped 3% over the year, and 8% in film, LPDE's largest market. Polypropylene's two largest U.S. markets, molding and fibers, have also dropped sharply. Epoxy resin showed a May 1979 to May 1980 gain of 28% in exports, but three other thermosets, polyesters, urea-melamine, and phenolics, have dropped sharply since May 1979.

  18. Universality in freezing of an asymmetric drop

    NASA Astrophysics Data System (ADS)

    Ismail, Md Farhad; Waghmare, Prashant R.

    2016-12-01

    We present the evidence of universality in conical tip formation during the freezing of arbitrary-shaped sessile droplets. The focus is to demonstrate the relationship between this universality and the liquid drop shape. We observe that, in the case of asymmetric drops, this universal shape is achieved when the tip reconfigures by changing its location, which subsequently alters the frozen drop shape. The proposed "two-triangle" model quantifies the change in the tip configuration as a function of the asymmetry of the drop that shows a good agreement with the experimental evidence. Finally, based on the experimental and theoretical exercise, we propose the scaling dependence between the variations in the tip configuration and the asymmetry of the drop.

  19. Patients dropping out of treatment in Italy.

    PubMed

    Morlino, M; Martucci, G; Musella, V; Bolzan, M; de Girolamo, G

    1995-07-01

    The aim of this study was to explore the extent and the specific features of drop-out for patients having a first contact with an university psychiatric outpatient clinic in Italy over the course of 1 year and to determine which variables were associated with early termination of treatment. Of the 158 patients selected for this study, there was an overall 3-month drop-out rate following the first visit of 63%. Of the 59 patients who had returned once after the initial contact, 28 interrupted subsequently the treatment, although the therapist's plan included further visits. The overall drop-out rate at 3 months was thus 82%. The only 2 variables associated with drop-out rates were the patients' perception of the severity of their disorder and the psychiatric history: continuing patients were more frequently in agreement with the clinician's judgment as compared with those who dropped out and were more likely to have already been in psychiatric treatment.

  20. Particle-drop Impact in Midair

    NASA Astrophysics Data System (ADS)

    Amirfazli, Alidad; Strzebin, Stefan; Peise, Oliver; Chevrollier, David

    2011-11-01

    For the first time the impact of a drop and particle in the mid-air is studied, which is a fundamental physical phenomenon relevant to many applications involving a fluidized bed and a liquid jet, e.g. drug particle coating, and upgrading of heavy oil. To date it has not been clear what happens when a particle and drop collide in midair. An apparatus was build to allow deterministic impact of a particle and drop to occur in midair. Using high speed imaging the impact of three different particles with water drops is studied at different relative velocities. Possible collision outcomes are elucidated in terms of particle-drop diameter ratio, Weber number, and particle wettability. Three distinct regimes of bonding, ripping and coating, and shattering are identified and discussed in this novel study. The differences between on-axis versus off-axis impact is also briefly discussed. NSERC & Canada Research Chairs.

  1. Dynamic Stability of Equilibrium Capillary Drops

    NASA Astrophysics Data System (ADS)

    Feldman, William M.; Kim, Inwon C.

    2014-03-01

    We investigate a model for contact angle motion of quasi-static capillary drops resting on a horizontal plane. We prove global in time existence and long time behavior (convergence to equilibrium) in a class of star-shaped initial data for which we show that topological changes of drops can be ruled out for all times. Our result applies to any drop which is initially star-shaped with respect to a small ball inside the drop, given that the volume of the drop is sufficiently large. For the analysis, we combine geometric arguments based on the moving-plane type method with energy dissipation methods based on the formal gradient flow structure of the problem.

  2. CPAS Preflight Drop Test Analysis Process

    NASA Technical Reports Server (NTRS)

    Englert, Megan E.; Bledsoe, Kristin J.; Romero, Leah M.

    2015-01-01

    Throughout the Capsule Parachute Assembly System (CPAS) drop test program, the CPAS Analysis Team has developed a simulation and analysis process to support drop test planning and execution. This process includes multiple phases focused on developing test simulations and communicating results to all groups involved in the drop test. CPAS Engineering Development Unit (EDU) series drop test planning begins with the development of a basic operational concept for each test. Trajectory simulation tools include the Flight Analysis and Simulation Tool (FAST) for single bodies, and the Automatic Dynamic Analysis of Mechanical Systems (ADAMS) simulation for the mated vehicle. Results are communicated to the team at the Test Configuration Review (TCR) and Test Readiness Review (TRR), as well as at Analysis Integrated Product Team (IPT) meetings in earlier and intermediate phases of the pre-test planning. The ability to plan and communicate efficiently with rapidly changing objectives and tight schedule constraints is a necessity for safe and successful drop tests.

  3. Thermal activation of superheated lipid-coated perfluorocarbon drops.

    PubMed

    Mountford, Paul A; Thomas, Alec N; Borden, Mark A

    2015-04-28

    This study explored the thermal conditions necessary for the vaporization of superheated perfluorocarbon nanodrops. Droplets C3F8 and C4F10 coated with a homologous series of saturated diacylphosphatidylcholines were formed by condensation of 4 μm diameter microbubbles. These drops were stable at room temperature and atmospheric pressure, but they vaporized back into microbubbles at higher temperatures. The vaporization transition was measured as a function of temperature by laser light extinction. We found that C3F8 and C4F10 drops experienced 90% vaporization at 40 and 75 °C, respectively, near the theoretical superheat limits (80-90% of the critical temperature). We therefore conclude that the metastabilty of these phase-change agents arises not from the droplet Laplace pressure altering the boiling point, as previously reported, but from the metastability of the pure superheated fluid to homogeneous nucleation. The rate of C4F10 drop vaporization was quantified at temperatures ranging from 55 to 75 °C, and an apparent activation energy barrier was calculated from an Arrhenius plot. Interestingly, the activation energy increased linearly with acyl chain length from C14 to C20, indicating that lipid interchain cohesion plays an important role in suppressing the vaporization rate. The vaporized drops (microbubbles) were found to be unstable to dissolution at high temperatures, particularly for C14 and C16. However, proper choice of the fluorocarbon and lipid species provided a nanoemulsion that could undergo at least ten reversible condensation/vaporization cycles. The vaporization properties presented in this study may facilitate the engineering of tunable phase-shift particles for diagnostic imaging, targeted drug delivery, tissue ablation, and other applications.

  4. Drop Tower Facility at Queensland University of Technology

    NASA Astrophysics Data System (ADS)

    Plagens, Owen; Castillo, Martin; Steinberg, Theodore; Ong, Teng-Cheong

    The Queensland University of Technology (QUT) Drop Tower Facility is a {raise.17exscriptstyle˜}2.1 second, 21.3 m fall, dual capsule drop tower system. The dual capsule comprises of an uncoupled exterior hollow drag shield that experiences drag by the ambient atmosphere with the experimental capsule falling within the drag shield. The dual capsule system is lifted to the top of the drop tower via a mechanical crane and the dropping process is initiated by the cutting of a wire coupling the experimental package and suspending the drag shield. The internal experimental capsule reaches the bottom of the drag shield floor just prior to the deceleration stage at the air bag and during this time experience gravity levels of {raise.17exscriptstyle˜}10textsuperscript{-6} g. The deceleration system utilizes an inflatable airbag where experimental packages can be designed to experience a maximum deceleration of {raise.17exscriptstyle˜}10textsuperscript{18} g for {raise.17exscriptstyle˜}0.1 seconds. The drag shield can house experimental packages with a maximum diameter of 0.8 m and height of 0.9 m. The drag shield can also be used in foam mode, where the walls are lined with foam and small experiments can be dropped completely untethered. This mode is generally used for the study of microsatellite manipulation. Payloads can be powered by on-board power systems with power delivered to the experiment until free fall occurs. Experimental data that can be collected includes but is not limited to video, temperature, pressure, voltage/current from the power supply, and triggering mechanisms outputs which are simultaneously collected via data logging systems and high speed video recording systems. Academic and commercial projects are currently under investigation at the QUT Drop Tower Facility and collaboration is openly welcome at this facility. Current research includes the study of heterogeneously burning metals in oxygen which is aimed at fire safety applications and

  5. Blown Away: The Shedding and Oscillation of Sessile Drops by Cross Flowing Air

    NASA Astrophysics Data System (ADS)

    Milne, Andrew James Barnabas

    For drops sessile on a solid surface, cross flowing air can drive drop oscillation or shedding, based on the balance and interaction of aerodynamic drag force (based on drop size/shape and air speed) and adhesion/capillary forces (based on surface tension and drop size/shape). Better understanding of the above has applications to, e.g., fuel cell flooding, airfoil icing, and visibility in rain. To understand the basic physics, experiments studying individual sessile drops in a low speed wind tunnel were performed in this thesis. Analysis of high speed video gave time resolved profiles and airspeed for shedding. Testing 0.5 mul to 100 mul drops of water and hexadecane on poly(methyl methacrylate) PMMA, Teflon, and a superhydrophobic surface (SHS) yielded a master curve describing critical airspeed for shedding for water drops on all surface tested. This curve predicts behavior for new surfaces, and explains experimental results published previously. It also indicates that the higher contact angle leads to easier shedding due to decreased adhesion and increased drag. Developing a novel floating element differential drag sensor gave the first measurements of the microNewton drag force experienced by drops. Forces magnitude is comparable to gravitational shedding from a tilted plate and to simplified models for drop adhesion, with deviations that suggest effects due to the air flow. Fluid properties are seen to have little effect on drag versus airspeed, and decreased adhesion is seen to be more important than increased drag for easing shedding. The relation between drag coefficient and Reynolds number increases slightly with liquid-solid contact angle, and with drop volume. Results suggest that the drop experiences increased drag compared to similarly shaped solid bodies due to drop oscillations aeroelasticly coupling into the otherwise laminar flow. The bulk and surface oscillations of sessile drops in cross flow was also studied, using a full profile analysis

  6. An investigation on the motion and deformation of viscoelastic drops descending in another viscoelastic media

    NASA Astrophysics Data System (ADS)

    Davoodi, M.; Norouzi, M.

    2016-10-01

    In the present study, an investigation of the motion and shape deformation of drops is carried out in creeping flow to highlight the effect of viscoelastic properties on the problem. A perturbation method is employed to derive an analytical solution for the general case that both interior and exterior fluids are viscoelastic, both fluids obeying the Giesekus model. An experiment is also performed for the limiting case of an immiscible drop of a 0.03% (w/w) polyacrylamide in an 80:20 glycerol/water solution falling through a viscous Newtonian silicon oil (410 cP polydimethylsiloxane oil) in order to check the accuracy of the analytical solution. It is shown that the addition of elastic properties to the interior fluid may cause a decrease in the terminal velocity of the droplet while an increase in the elastic properties of the exterior fluid results in the opposite behavior and increases the terminal velocity. The well-known spherical shape of creeping drops for Newtonian fluids is modified by elasticity into either prolate or oblate shapes. Using the analytical solution, it is shown that normal stresses play a key role on the final steady-state shape of the drops. To keep the drops spherical in viscoelastic phases, it is shown that the effect of normal stresses on the interior and exterior media can cancel out under certain conditions. The results presented here may be of interest to industries dealing with petroleum and medicine processing, paint and power-plant related fields where knowledge of the shape and terminal velocity of descending droplets is of great importance.

  7. Condensation on surface energy gradient shifts drop size distribution toward small drops.

    PubMed

    Macner, Ashley M; Daniel, Susan; Steen, Paul H

    2014-02-25

    During dropwise condensation from vapor onto a cooled surface, distributions of drops evolve by nucleation, growth, and coalescence. Drop surface coverage dictates the heat transfer characteristics and depends on both drop size and number of drops present on the surface at any given time. Thus, manipulating drop distributions is crucial to maximizing heat transfer. On earth, manipulation is achieved with gravity. However, in applications with small length scales or in low gravity environments, other methods of removal, such as a surface energy gradient, are required. This study examines how chemical modification of a cooled surface affects drop growth and coalescence, which in turn influences how a population of drops evolves. Steam is condensed onto a horizontally oriented surface that has been treated by silanization to deliver either a spatially uniform contact angle (hydrophilic, hydrophobic) or a continuous radial gradient of contact angles (hydrophobic to hydrophilic). The time evolution of number density and associated drop size distributions are measured. For a uniform surface, the shape of the drop size distribution is unique and can be used to identify the progress of condensation. In contrast, the drop size distribution for a gradient surface, relative to a uniform surface, shifts toward a population of small drops. The frequent sweeping of drops truncates maturation of the first generation of large drops and locks the distribution shape at the initial distribution. The absence of a shape change indicates that dropwise condensation has reached a steady state. Previous reports of heat transfer enhancement on chemical gradient surfaces can be explained by this shift toward smaller drops, from which the high heat transfer coefficients in dropwise condensation are attributed to. Terrestrial applications using gravity as the primary removal mechanism also stand to benefit from inclusion of gradient surfaces because the critical threshold size required for

  8. The Parkfield Stress Drop Controversy

    NASA Astrophysics Data System (ADS)

    Abercrombie, R. E.; Nadeau, R. M.

    2003-12-01

    Nadeau et al. (1995) found that the seismicity on the San Andreas fault at Parkfield is highly clustered. Individual clusters consist of a sequence of near periodically repeating small earthquakes of similar seismic moment. Nadeau and Johnston (1998) compared the moments and timing of these repeating earthquakes (Mw < 2), and some larger events, with the surface creep rate on the fault to estimate the slip and stress drop (Δ σ ). They obtained conventional values (0.1 to 10 MPa) for the larger earthquakes, but Δ σ increased with decreasing Mw to extremely high values (> 1000 MPa) for the small earthquakes (Mw < 2). Such values are just about physically possible, but they are much higher than those estimated by seismic methods for small earthquakes elsewhere (e. g. Abercrombie 1995). These controversial high Δ σ estimates have sparked a number of theoretical and laboratory studies (e. g. Sammis & Rice 2000, Anooshepoor & Brune 2001, Beeler 2001) aimed at investigating whether the observations could result from earthquakes with more normal Δ σ occurring within the unusual tectonic setting at Parkfield. Lane & Nadeau (2000, 2002) considered whether localized patches of high Δ σ would be resolvable by standard seismic methods. However, to date nobody has used seismic methods to determine source parameters for these controversial small earthquakes at Parkfield. We use closely located earthquakes of different sizes (for example, the sub-clusters of cluster CL14, Nadeau et al., 1995, Mw-0.2 to 1), recorded on the HRSN borehole network to analyse the source parameters. The smaller earthquakes are used as empirical Green's functions to resolve source processes of the larger events. Preliminary results from the earthquakes in cluster CL14 result in a source dimension of about 25 m and Δ σ of about 1 MPa for the Mw1 earthquakes, assuming that rupture velocity is the same as that for large earthquakes. We also resolve source-time functions for these earthquakes at

  9. Ground Based Studies of Thermocapillary Flows in Levitated Drops: Analytical Part

    NASA Technical Reports Server (NTRS)

    Sadhal, S. S.; Trinh, Eugene H.

    1997-01-01

    The main objectives of the analytical part of this investigation are to study the fluid flow phenomena together with the thermal effects on drops levitated in an acoustic field. To a large extent, experimentation on ground requires a strong acoustic field that has a significant interference with other thermal-fluid effects. While most of the work has been directed towards particles in strong acoustic fields to overcome gravity, some results for microgravity have been obtained. One of the objectives was to obtain the thermocapillary flow in a spot-heated drop, and set up a model for the prediction of thermophysical properties. In addition, for acoustically levitated particles, a clear understanding of the underlying fluid mechanics was required. Also, the interaction of acoustics with steady and pulsating thermal stimuli was required to be analyzed. The experimental part of the work was funded through JPL, and has been reported separately.

  10. The Drop Tower Bremen -An Overview

    NASA Astrophysics Data System (ADS)

    von Kampen, Peter; Könemann, Thorben; Rath, Hans J.

    The Center of Applied Space Technology and Microgravity (ZARM) was founded in 1985 as an institute of the University of Bremen, which focuses on research on gravitational and space-related phenomena. In 1988, the construction of ZARM`s drop tower began. Since its inau-guration in September 1990, the eye-catching Drop Tower Bremen with a height of 146m and its characteristic glass roof has become twice a landmark on the campus of the University of Bremen and the emblem of the technology park Bremen. As such an outstanding symbol of space science in Bremen the drop tower provides an european unique facility for experiments under conditions of high-quality weightlessness with residual gravitational accelerations in the microgravity regime. The period of maximum 4.74s of each freely falling experiment at the Drop Tower Bremen is only limited by the height of the drop tower vacuum tube, which was fully manufactured of steal and enclosed by an outer concrete shell. Thus, the pure free fall height of each microgravity drop experiment is approximately 110m. By using the later in-stalled catapult system established in 2004 ZARM`s short-term microgravity laboratory is able to nearly double the time of free fall. This world-wide inimitable capsule catapult system meets scientists` demand of extending the period of weightlessness. During the catapult operation the experiment capsule performs a vertical parabolic flight within the drop tower vacuum tube. In this way the time of microgravity can be extended to slightly over 9s. Either in the drop or in the catapult operation routine the repetition rates of microgravity experiments at ZARM`s drop tower facility are the same, generally up to 3 times per day. In comparison to orbital platforms the ground-based laboratory Drop Tower Bremen represents an economic alternative with a permanent access to weightlessness on earth. Moreover, the exceptional high quality of weightlessness in order of 1e-6 g (in the frequency range below 100

  11. Surface tension effects in levitated helium drops

    NASA Astrophysics Data System (ADS)

    Vicente, Carlos Luis

    We report our investigations of surface tension driven flows in magnetically levitated 4He drops. By levitating helium drops in a magnetic trap we are able to observe the free surface of drops as they undergo shape oscillations. We also study the dynamics of the free surface during the process of coalescence. Our experimental method allows us to excite shape oscillations in the levitated helium drops and measure their normal mode frequencies. By measuring the frequency of the fundamental (l = 2) mode, we obtain new measurements of the surface tension of helium for temperatures between 1.5 and 0.5 K. Our measurements extrapolate to a value of 0.375 erg cm -2 at T = 0 K. Our results agree with the capillary wave measurements of Roche et al., and Atkins and Narahra. We study how the shape of the trap used to levitate the drops influences the resonant frequency of the l = 2 mode. Measurements of the frequency spectrum were performed using different trap potentials. We have calculated the resonant frequencies for the trap shapes produced by different magnet coil currents. We compare our measurements of the resonant frequencies at various magnet currents with these theoretical predictions and find good agreement. We describe experiments to study the coalescence of He II drops levitated in a magnetic trap. Using a high speed CCD camera, we have produced movies of drops coalescing at temperatures as low as 0.7 K. We examine some interesting features of the motion during and following coalescence.

  12. Interaction of Drops on a Soft Substrate

    NASA Astrophysics Data System (ADS)

    Lubbers, Luuk A.; Weijs, Joost H.; Das, Siddhartha; Botto, Lorenzo; Andreotti, Bruno; Snoeijer, Jacco H.

    2013-11-01

    A sessile drop can elastically deform a substrate by the action of capillary forces. The typical size of the deformation is given by the ratio of surface tension and the elastic modulus, γ / E , which can reach up to 10-100 microns for soft elastomers. In this talk we theoretically show that the contact angles of drops on such a surface exhibit two transitions when increasing γ / E : (i) the microsocopic geometry of the contact line first develops a Neumann-like cusp when γ / E is of the order of few nanometers, (ii) the macroscopic angle of the drop is altered only when γ / E reaches the size of the drop. Using the same framework we then show that two neighboring drops exhibit an effective interaction, mediated by the deformation of the elastic medium. This is in analogy to the well-known Cheerios effect, where small particles at a liquid interface attract eachother due to the meniscus deformations. Here we reveal the nature of drop-drop interactions on a soft substrate by combining numerical and analytical calculations.

  13. Drop rebound in clouds and precipitation

    NASA Technical Reports Server (NTRS)

    Ochs, H. T., III; Beard, K. V.

    1982-01-01

    The possibility of rebound for colliding cloud drops was measured by determining the collection efficiency. The collection efficiency for 17 size pairs of relatively uncharged drops in over 500 experimental runs was measured using two techniques. The collection efficiencies fall in a narrow range of 0.60 to 0.70 even though the collection drop was varied between 63 and 326 microns and the size ratio from 0.05 to 0.33. In addition the measured values of collection efficiencies (Epsilon) were below the computed values of collision efficiencies (E) for rigid spheres. Therefore it was concluded that rebound was occurring for these sizes since inferred coalescence (epsilon = Epsilon/E) efficiencies are about 0.6 yo 0.8. At a very small size ratio (r/R = p = 0.05, R = 326 microns) the coalescence efficiency inferred is in good agreement with the experimental findings for a supported collector drop. At somewhat large size ratios the inferred values of epsilon are well above results of supported drop experiments, but show a slight correspondence in collected drop size dependency to two models of drop rebound. At a large size ratio (p = 0.73, R = 275) the inferred coalescence efficiency is significantly different from all previous results.

  14. Laplacian drop shapes and effect of random perturbations on accuracy of surface tension measurement for different drop constellations.

    PubMed

    Saad, Sameh M I; Neumann, A Wilhelm

    2015-08-01

    Theoretical drop shapes are calculated for three drop constellations: pendant drops, constrained sessile drops, and unconstrained sessile drops. Based on total Gaussian curvature, shape parameter and critical shape parameter are discussed as a function of different drop sizes and surface tensions. The shape parameter is linked to physical parameters for every drop constellation. The as yet unavailable detailed dimensional analysis for the unconstrained sessile drop is presented. Results show that the unconstrained sessile drop shape depends on a dimensionless volume term and the contact angle. Random perturbations are introduced and the accuracy of surface tension measurement is assessed for precise and perturbed profiles of the three drop constellations. It is concluded that pendant drops are the best method for accurate surface tension measurement, followed by constrained sessile drops. The unconstrained sessile drops come last because they tend to be more spherical at low and moderate contact angles. Of course, unconstrained sessile drops are the only option if contact angles are to be measured.

  15. Microjetting from wave focusing on oscillating drops

    NASA Astrophysics Data System (ADS)

    Thoroddsen, S. T.; Etoh, T. G.; Takehara, K.

    2007-05-01

    We present experimental observations of microjetting from an oscillating drop. The jet is generated by the focusing of axisymmetric capillary waves that overturn and collide at an apex of the drop. These jets are up to two orders of magnitude smaller than the original drops. We present two widely different configurations that produce such microjets. The first occurs on a satellite drop, produced by the pinch-off of a water drop from a vertical nozzle. The large oscillations following the contraction of the satellite bridge focus waves at the bottom, sending out a 30μm jet at 9.9m/s. The second jet arises when a water drop, containing surfactants, falls onto and passes through a hemispherical soap film. The gentle deformation of the drop creates a surface wave that focuses at its top, shooting out a tiny jet and entrapping a small bubble inside the drop. This jet is 16±5μm in diameter and emerges at 6.3m/s. In this configuration, the soap film wraps around the drop and acts as a sensor of the air flow, revealing that the liquid jet is preceded by a localized faster-moving air jet. The jetting in both configurations is quite robust and occurs even for slightly asymmetric conditions. These microjets appear for much lower values of the Reynolds and Weber numbers than previously observed, suggesting that free-surface jetting is not limited to the inviscid capillary-inertial regime, which has been the focus of much of the theoretical work.

  16. [Dropped head syndrome in motor neuron disease].

    PubMed

    Lorenzoni, Paulo José; Lange, Marcos Christiano; Kay, Cláudia S K; Almeida, Luiz G M P de; Teive, Hélio A G; Scola, Rosana H; Werneck, Lineu C

    2006-03-01

    Dropped head is a syndrome caused by weakness of the neck extensor muscles found in different kinds of neuromuscular disorders and also in amyotrophic lateral sclerosis. This is a cases report of three women with motor neuron disease with beginning of dysphagia and cervical weakness that it evolved with dropped head. The investigation showed normal magnetic resonance imaging of brain and cervical column. Needle electromyography showed active and chronic denervation in bulbar muscles and cervical, thoracic and lumbosacral segments. We discuss the characteristic of disease, specially the clinical manifestations and electromyography features, with emphasis at the clinical evaluation of dropped head in the suspicion of motor neuron disease.

  17. Condensation-induced jumping water drops.

    PubMed

    Narhe, R D; Khandkar, M D; Shelke, P B; Limaye, A V; Beysens, D A

    2009-09-01

    Water droplets can jump during vapor condensation on solid benzene near its melting point. This phenomenon, which can be viewed as a kind of micro scale steam engine, is studied experimentally and numerically. The latent heat of condensation transferred at the drop three phase contact line melts the substrate during a time proportional to R (the drop radius). The wetting conditions change and a spontaneous jump of the drop results in random direction over length approximately 1.5R , a phenomenon that increases the coalescence events and accelerates the growth. Once properly rescaled by the jump length scale, the growth dynamics is, however, similar to that on a solid surface.

  18. Condensation-induced jumping water drops

    NASA Astrophysics Data System (ADS)

    Narhe, R. D.; Khandkar, M. D.; Shelke, P. B.; Limaye, A. V.; Beysens, D. A.

    2009-09-01

    Water droplets can jump during vapor condensation on solid benzene near its melting point. This phenomenon, which can be viewed as a kind of micro scale steam engine, is studied experimentally and numerically. The latent heat of condensation transferred at the drop three phase contact line melts the substrate during a time proportional to R (the drop radius). The wetting conditions change and a spontaneous jump of the drop results in random direction over length ˜1.5R , a phenomenon that increases the coalescence events and accelerates the growth. Once properly rescaled by the jump length scale, the growth dynamics is, however, similar to that on a solid surface.

  19. Rotation of ultrasonically levitated glycerol drops

    NASA Technical Reports Server (NTRS)

    Biswas, A.; Leung, E. W.; Trinh, E. H.

    1991-01-01

    Ultrasonic levitation is used to suspend single millimeter-size glycerol drops in a rectangular chamber. Audio-frequency laterally standing waves set up in the chamber are used to torque the suspended drops. The shape evolution of the drop under the combined effect of centrifugal forces and the acoustic radiation stress, along with its angular velocity are monitored, using video imaging and light scattering techniques. The results show good qualitative agreement with the theoretically predicted shape evolution as a function of angular velocity.

  20. Electrohydrodynamic removal of particles from drop surfaces.

    PubMed

    Nudurupati, S; Janjua, M; Singh, P; Aubry, N

    2009-07-01

    A uniform electric field is used for cleaning drops of the particles they often carry on their surface. In a first step, particles migrate to either the drop's poles or equator. This is due to the presence of an electrostatic force for which an analytical expression is derived. In a second step, particles concentrated near the poles are released into the ambient liquid via tip streaming, and those near the equator are removed by stretching the drop and breaking it into several droplets. In the latter case, particles are all concentrated in a small middle daughter droplet.

  1. Aerodynamic and engineering design of a 1.5 s high quality microgravity drop tower facility

    NASA Astrophysics Data System (ADS)

    Belser, Valentin; Breuninger, Jakob; Reilly, Matthew; Laufer, René; Dropmann, Michael; Herdrich, Georg; Hyde, Truell; Röser, Hans-Peter; Fasoulas, Stefanos

    2016-12-01

    Microgravity experiments are essential for research in space science, biology, fluid mechanics, combustion, and material sciences. One way to conduct microgravity experiments on Earth is by using drop tower facilities. These facilities combine a high quality of microgravity, adequate payload masses and have the advantage of virtually unlimited repeatability under same experimental conditions, at a low cost. In a collaboration between the Institute of Space Systems (IRS) at the University of Stuttgart and Baylor University (BU) in Waco, Texas, a new drop tower is currently under development at the Center for Astrophysics, Space Physics and Engineering Research (CASPER). The design parameters of the drop tower ask for at least 1.5 s in free fall duration while providing a quality of at least 10-5 g. Previously, this quality has only been achieved in vacuum drop tower facilities where the capsule experiences virtually zero aerodynamic drag during its free fall. Since this design comes at high costs, a different drop tower design concept, which does not require an evacuated drop shaft, was chosen. It features a dual-capsule system in which the experiment capsule is shielded from aerodynamic forces by surrounding it with a drag shield during the drop. As no other dual-capsule drop tower has been able to achieve a quality as good as or better than 10-5 g previous work optimized the design with an aerodynamic perspective by using computational fluid dynamics (CFD) simulations to determine the ideal shape and size of the outer capsule and to specify the aerodynamically crucial dimensions for the overall system. Experiments later demonstrated that the required quality of microgravity can be met with the proposed design. The main focus of this paper is the mechanical realization of the capsule as well as the development and layout of the surrounding components, such as the release mechanism, the deceleration device and the drop shaft. Because the drop tower facility is a

  2. Getting in shape: molten wax drop deformation and solidification at an immiscible liquid interface.

    PubMed

    Beesabathuni, Shilpa N; Lindberg, Seth E; Caggioni, Marco; Wesner, Chris; Shen, Amy Q

    2015-05-01

    The controlled production of non-spherical shaped particles is important for many applications such as food processing, consumer goods, adsorbents, drug delivery, and optical sensing. In this paper, we investigated the deformation and simultaneous solidification of millimeter size molten wax drops as they impacted an immiscible liquid interface of higher density. By varying initial temperature and viscoelasticity of the molten drop, drop size, impact velocity, viscosity and temperature of the bath fluid, and the interfacial tension between the molten wax and bath fluid, spherical molten wax drops impinged on a cooling water bath and were arrested into non-spherical solidified particles in the form of ellipsoid, mushroom, disc, and flake-like shapes. We constructed cursory phase diagrams for the various particle shapes generated over a range of Weber, Capillary, Reynolds, and Stefan numbers, governed by the interfacial, inertial, viscous, and thermal effects. We solved a simplified heat transfer problem to estimate the time required to initiate the solidification at the interface of a spherical molten wax droplet and cooling aqueous bath after impact. By correlating this time with the molten wax drop deformation history captured from high speed imaging experiments, we elucidate the delicate balance of interfacial, inertial, viscous, and thermal forces that determine the final morphology of wax particles.

  3. A comparison of boundary element and finite element methods for modeling axisymmetric polymeric drop deformation

    NASA Astrophysics Data System (ADS)

    Hooper, Russell; Toose, Matthijs; Macosko, Christopher W.; Derby, Jeffrey J.

    2001-12-01

    A modified boundary element method (BEM) and the DEVSS-G finite element method (FEM) are applied to model the deformation of a polymeric drop suspended in another fluid subjected to start-up uniaxial extensional flow. The effects of viscoelasticity, via the Oldroyd-B differential model, are considered for the drop phase using both FEM and BEM and for both the drop and matrix phases using FEM. Where possible, results are compared with the linear deformation theory. Consistent predictions are obtained among the BEM, FEM, and linear theory for purely Newtonian systems and between FEM and linear theory for fully viscoelastic systems. FEM and BEM predictions for viscoelastic drops in a Newtonian matrix agree very well at short times but differ at longer times, with worst agreement occurring as critical flow strength is approached. This suggests that the dominant computational advantages held by the BEM over the FEM for this and similar problems may diminish or even disappear when the issue of accuracy is appropriately considered. Fully viscoelastic problems, which are only feasible using the FEM formulation, shed new insight on the role of viscoelasticity of the matrix fluid in drop deformation. Copyright

  4. Motion of Drops on Surfaces with Wettability Gradients

    NASA Technical Reports Server (NTRS)

    Subramanian, R. Shankar; McLaughlin, John B.; Moumen, Nadjoua; Qian, Dongying

    2002-01-01

    desiccator. This is done using an approximate line source of the vapor in the form of a string soaked in the alkylchlorosilane. Ordinarily, many fluids, including water, wet the surface of silicon quite well. This means that the contact angle is small. But the silanized surface resists wetting, with contact angles that are as large as 100 degs. Therefore, a gradient of wettability is formed on the silicon surface. The region near the string is highly hydrophobic, and the contact angle decreases gradually toward a small value at the hydrophilic end away from this region. The change in wettability occurs over a distance of several mm. The strip is placed on a platform within a Plexiglas cell. Drops of a suitable liquid are introduced on top of the strip near the hydrophobic end. An optical system attached to a video camera is trained on the drop so that images of the moving drop can be captured on videotape for subsequent analysis. We have performed preliminary experiments with water as well as ethylene glycol drops. Results from these experiments will be presented in the poster. Future plans include the refinement of the experimental system so as to permit images to be recorded from the side as well as the top, and the conduct of a systematic study in which the drop size is varied over a good range. Experiments will be conducted with different fluids so as to obtain the largest possible range of suitably defined Reynolds and Capillary numbers. Also, an effort will be initiated on theoretical modeling of this motion. The challenges in the development of the theoretical description lie in the proper analysis of the region in the vicinity of the contact line, as well as in the free boundary nature of the problem. It is known that continuum models assuming the no slip condition all the way to the contact line fail by predicting that the stress on the solid surface becomes singular as the contact line is approached. One approach for dealing with this issue has been to relax the no

  5. PS foams at high pressure drop rates

    NASA Astrophysics Data System (ADS)

    Tammaro, Daniele; De Maio, Attilio; Carbone, Maria Giovanna Pastore; Di Maio, Ernesto; Iannace, Salvatore

    2014-05-01

    In this paper, we report data on PS foamed at 100 °C after CO2 saturation at 10 MPa in a new physical foaming batch that achieves pressure drop rates up to 120 MPa/s. Results show how average cell size of the foam nicely fit a linear behavior with the pressure drop rate in a double logarithmic plot. Furthermore, foam density initially decreases with the pressure drop rate, attaining a constant value at pressure drop rates higher than 40 MPa/s. Interestingly, furthermore, we observed that the shape of the pressure release curve has a large effect on the final foam morphology, as observed in tests in which the maximum pressure release rate was kept constant but the shape of the curve changed. These results allow for a fine tuning of the foam density and morphology for specific applications.

  6. Pressure drop in two-phase flow

    NASA Astrophysics Data System (ADS)

    Akashah, S. A.

    1980-12-01

    A computer program was developed containing some of the methods for predicting pressure drop in two-phase flow. The program contains accurate methods for predicting phase behavior and physical properties and can be used to calculate pressure drops for horizontal, inclined and vertical phases. The program was used to solve test cases for many types of flow, varying the diameter, roughness, composition, overall heat transfer coefficient, angle of inclination, and length. The Lockhart-Martinelli correlation predicts the highest pressure drop while the Beggs and Brill method predicts the lowest. The American Gas Association-American Petroleum Institute method is consistent and proved to be reliable in vertical, horizontal and inclined flow. The roughness of the pipe diameter had great effect on pressure drop in two-phase flow, while the overall heat transfer coefficient had little effect.

  7. How to Use Eye Drops Properly

    MedlinePlus

    ... doses Use the exact number of drops recommended Store medications out of reach of children Copyright 2013, American Society of Health-System Pharmacists. All rights reserved. This material may not be reproduced, displayed, modified, or distributed ...

  8. How to Use Nose Drops Properly

    MedlinePlus

    ... Use nose drops only as long as directed Store medications out of reach of children Copyright 2013, American Society of Health-System Pharmacists. All rights reserved. This material may not be reproduced, displayed, modified, or distributed ...

  9. Electric field induced deformation of sessile drops

    NASA Astrophysics Data System (ADS)

    Corson, Lindsey; Tsakonas, Costas; Duffy, Brian; Mottram, Nigel; Brown, Carl; Wilson, Stephen

    2014-11-01

    The ability to control the shape of a drop with the application of an electric field has been exploited for many technological applications including measuring surface tension, producing an optical display device, and optimising the optical properties of microlenses. In this work we consider, both theoretically and experimentally, the deformation of pinned sessile drops with contact angles close to either 0° or 90° resting on the lower substrate inside a parallel plate capacitor due to an A.C. electric field. Using both asymptotic and numerical approaches we obtain predictive equations for the static and dynamic drop shape deformations as functions of the key experimental parameters (drop size, capacitor plate separation, electric field magnitude and contact angle). The asymptotic results agree well with the experimental results for a range of liquids. We gratefully acknowledge the financial support of EPSRC via research Grants EP/J009865 and EP/J009873.

  10. Abortions in Texas Dropped Dramatically After Restrictions

    MedlinePlus

    ... page: https://medlineplus.gov/news/fullstory_163136.html Abortions in Texas Dropped Dramatically After Restrictions Greater travel ... later declared unconstitutional -- that increased travel distances to abortion clinics in the state seems to have led ...

  11. Drop dynamics in space. [for space processing

    NASA Technical Reports Server (NTRS)

    Wang, T. G.; Saffren, M. M.; Elleman, D. D.

    1977-01-01

    Experiments to study the dynamics of liquid drops are being planned to be performed in the weightless environment of Spacelab. The liquids will range from superfluid helium through ordinary liquid to molten metals and glasses. The experiments will be conducted in a chamber now being developed which utilizes the forces and torques produced by acoustic waves excited within the chamber. None of the currently available facilities (drop towers, sounding rockets, or zero-g aircraft flights) can provide a sustained weightless environment, since the resulting zero-g periods are from 3 sec to 5 min. Spaceflight, however, will provide weightlessness for periods of one week, or more, allowing truly laboratory-like experiments to be conducted on free liquid drops and bubbles. In this paper we discuss both the drop dynamics experiments proposed for Spacelab and the acoustic chamber: its operation and current testing for these and other experiments.

  12. Spreading of liquid drops over porous substrates.

    PubMed

    Starov, V M; Zhdanov, S A; Kosvintsev, S R; Sobolev, V D; Velarde, M G

    2003-07-01

    The spreading of small liquid drops over thin and thick porous layers (dry or saturated with the same liquid) has been investigated in the case of both complete wetting (silicone oils of different viscosities) and partial wetting (aqueous SDS solutions of different concentrations). Nitrocellulose membranes of different porosity and different average pore size have been used as a model of thin porous layers, glass and metal filters have been used as a model of thick porous substrates. The first problem under investigation has been the spreading of small liquid drops over thin porous layers saturated with the same liquid. An evolution equation describing the drop spreading has been deduced, which showed that both an effective lubrication and the liquid exchange between the drop and the porous substrates are equally important. Spreading of silicone oils over different nitrocellulose microfiltration membranes was carried out. The experimental laws of the radius of spreading on time confirmed the theory predictions. The spreading of small liquid drops over thin dry porous layers has also been investigated from both theoretical and experimental points of view. The drop motion over a dry porous layer appears caused by the interplay of two processes: (a). the spreading of the drop over already saturated parts of the porous layer, which results in a growth of the drop base, and (b). the imbibition of the liquid from the drop into the porous substrate, which results in a shrinkage of the drop base and a growth of the wetted region inside the porous layer. As a result of these two competing processes the radius of the drop base goes through a maximum as time proceeds. A system of two differential equations has been derived to describe the time evolution of the radii of both the drop base and the wetted region inside the porous layer. This system includes two parameters, one accounts for the effective lubrication coefficient of the liquid over the wetted porous substrate, and

  13. Total Gaussian curvature, drop shapes and the range of applicability of drop shape techniques.

    PubMed

    Saad, Sameh M I; Neumann, A Wilhelm

    2014-02-01

    Drop shape techniques are used extensively for surface tension measurement. It is well-documented that, as the drop/bubble shape becomes close to spherical, the performance of all drop shape techniques deteriorates. There have been efforts quantifying the range of applicability of drop techniques by studying the deviation of Laplacian drops from the spherical shape. A shape parameter was introduced in the literature and was modified several times to accommodate different drop constellations. However, new problems arise every time a new configuration is considered. Therefore, there is a need for a universal shape parameter applicable to pendant drops, sessile drops, liquid bridges as well as captive bubbles. In this work, the use of the total Gaussian curvature in a unified approach for the shape parameter is introduced for that purpose. The total Gaussian curvature is a dimensionless quantity that is commonly used in differential geometry and surface thermodynamics, and can be easily calculated for different Laplacian drop shapes. The new definition of the shape parameter using the total Gaussian curvature is applied here to both pendant and constrained sessile drops as an illustration. The analysis showed that the new definition is superior and reflects experimental results better than previous definitions, especially at extreme values of the Bond number.

  14. Liquid drops on a surface: Using density functional theory to calculate the binding potential and drop profiles and comparing with results from mesoscopic modelling

    NASA Astrophysics Data System (ADS)

    Hughes, Adam P.; Thiele, Uwe; Archer, Andrew J.

    2015-02-01

    The contribution to the free energy for a film of liquid of thickness h on a solid surface due to the interactions between the solid-liquid and liquid-gas interfaces is given by the binding potential, g(h). The precise form of g(h) determines whether or not the liquid wets the surface. Note that differentiating g(h) gives the Derjaguin or disjoining pressure. We develop a microscopic density functional theory (DFT) based method for calculating g(h), allowing us to relate the form of g(h) to the nature of the molecular interactions in the system. We present results based on using a simple lattice gas model, to demonstrate the procedure. In order to describe the static and dynamic behaviour of non-uniform liquid films and drops on surfaces, a mesoscopic free energy based on g(h) is often used. We calculate such equilibrium film height profiles and also directly calculate using DFT the corresponding density profiles for liquid drops on surfaces. Comparing quantities such as the contact angle and also the shape of the drops, we find good agreement between the two methods. We also study in detail the effect on g(h) of truncating the range of the dispersion forces, both those between the fluid molecules and those between the fluid and wall. We find that truncating can have a significant effect on g(h) and the associated wetting behaviour of the fluid.

  15. La Gocciolina (The Little Drop of Water).

    ERIC Educational Resources Information Center

    Palandra, Maria

    This primary level reader in Italian intended for use in a bilingual education setting, is about the life cycle of a drop of water. The drop of water is personified and the story tells of its adventures as it travels from the top of the lake to the bottom, its meeting with the inhabitants of the lake, and its trip to the clouds. After deciding not…

  16. Bubble, Drop and Particle Unit (BDPU)

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This section of the Life and Microgravity Spacelab (LMS) publication includes the following articles entitled: (1) Oscillatory Thermocapillary Instability; (2) Thermocapillary Convection in Multilayer Systems; (3) Bubble and Drop Interaction with Solidification Front; (4) A Liquid Electrohydrodynamics Experiment; (5) Boiling on Small Plate Heaters under Microgravity and a Comparison with Earth Gravity; (6) Thermocapillary Migration and Interactions of Bubbles and Drops; and (7) Nonlinear Surface Tension Driven Bubble Migration

  17. Blood drop patterns: Formation and applications.

    PubMed

    Chen, Ruoyang; Zhang, Liyuan; Zang, Duyang; Shen, Wei

    2016-05-01

    The drying of a drop of blood or plasma on a solid substrate leads to the formation of interesting and complex patterns. Inter- and intra-cellular and macromolecular interactions in the drying plasma or blood drop are responsible for the final morphologies of the dried patterns. Changes in these cellular and macromolecular components in blood caused by diseases have been suspected to cause changes in the dried drop patterns of plasma and whole blood, which could be used as simple diagnostic tools to identify the health of humans and livestock. However, complex physicochemical driving forces involved in the pattern formation are not fully understood. This review focuses on the scientific development in microscopic observations and pattern interpretation of dried plasma and whole blood samples, as well as the diagnostic applications of pattern analysis. Dried drop patterns of plasma consist of intricate visible cracks in the outer region and fine structures in the central region, which are mainly influenced by the presence and concentration of inorganic salts and proteins during drying. The shrinkage of macromolecular gel and its adhesion to the substrate surface have been thought to be responsible for the formation of the cracks. Dried drop patterns of whole blood have three characteristic zones; their formation as functions of drying time has been reported in the literature. Some research works have applied engineering treatment to the evaporation process of whole blood samples. The sensitivities of the resultant patterns to the relative humidity of the environment, the wettability of the substrates, and the size of the drop have been reported. These research works shed light on the mechanisms of spreading, evaporation, gelation, and crack formation of the blood drops on solid substrates, as well as on the potential applications of dried drop patterns of plasma and whole blood in diagnosis.

  18. Program calculates two-phase pressure drop

    SciTech Connect

    Blackwell, W.W.

    1980-11-24

    Analysts have developed a program for determining the two-phase pressure drop in piping. Written for the TI-59 programmable calculator used with a PC-100C printer, the program incorporates several unique features: it calculates single-phase as well as two-phase pressure drops, has a 10-20 s execution time, permits the operating data to be changed easily, and includes an option for calculating the estimated surface tension of paraffinic hydrocarbon liquids.

  19. Stability of cefepime in aqueous eye drops.

    PubMed

    Kodym, A; Pawłowska, M; Rumiński, J K; Bartosińska, A; Kieliba, A

    2011-01-01

    The aim of the studies was to determine HPLC the stability of cefepime in 1% and 5% buffered eye drops of developed formulary composition, which were stored for 30 days at the temperature of 4 degrees C and 20 degrees C, protected from light. Separation was performed on RP18 Gemini octadecylsilane column (250 mm x 4.6 mm, 5.0 microm) at a temperature of 25 degrees C. The mobile phase consisted of 0.015 M solution of sodium salt of pentane sulphonic acid brought to pH 4.0 with glacial acetic acid and 45% KOH solution and acetonitrile 94:6 w/w, with detection of 254 nm. The method was linear in the range of 12.6-125 microg/ml (R2 = 0.9996). The limit of detection (LOD) was 3 microg/ml and limit of quantification (LOQ) was 10 microg/ml. 10% degradation of cefepime in 1% and 5% buffered eye drops stored at the temperature of 4 degrees C, depending on the composition of the eye drops, occurred after 21-27 days in 1% eye drops and 18-21 days in 5% eye drops. In the eye drops, which were stored at the temperature of 20 degrees C, 10% degradation of cefepime took place on the third day of storage regardless of formulary composition of 1% and 5% drops. Cefepime stability lasting a couple of weeks in 1% and 5% solution allows extemporaneous preparation of buffered eye drops containing cefepime.

  20. Quadratic formula for determining the drop size in pressure-atomized sprays with and without swirl

    NASA Astrophysics Data System (ADS)

    Lee, T.-W.; An, Keju

    2016-06-01

    We use a theoretical framework based on the integral form of the conservation equations, along with a heuristic model of the viscous dissipation, to find a closed-form solution to the liquid atomization problem. The energy balance for the spray renders to a quadratic formula for the drop size as a function, primarily of the liquid velocity. The Sauter mean diameter found using the quadratic formula shows good agreements and physical trends, when compared with experimental observations. This approach is shown to be applicable toward specifying initial drop size in computational fluid dynamics of spray flows.

  1. Non-axisymmetric shapes of a rotating drop in an immiscible system

    NASA Technical Reports Server (NTRS)

    Wang, T. G.; Tagg, R.; Cammack, L.; Croonquist, A. P.

    1982-01-01

    The nonaxisymmetric shapes of a rotating drop in an immiscible system were studied. Five basic families of shapes (axisymmetric, two-lobed, three-lobed, four-lobed, and toroidal) were observed. The sequence (axisymmetric to two-lobed to three-lobed to four-lobed to toroidal) seems to be linked to increasing spin-up velocity. For the axisymmetric case, direct comparisons of experiments with the theory of a free rotating drop were surprisingly good the equatorial area differs from theory by only 30%. Furthermore, the non-axisymmetric shapes are in good qualitative agreement with the theory, although the theory does not address the presence of an outer fluid.

  2. Dropped head syndrome in a patient with Aeromonas hydrophila-induced septic arthritis of the shoulder.

    PubMed

    Wang, Sheng-Huei; Juan, Chun-Jung; Lin, Te-Yu

    2014-12-01

    Septic arthritis of the shoulder is very rarely caused by Aeromonas hydrophila. We present the case of a 45-year-old woman who presented with symptoms of painful shoulder for 2 weeks and dropped head for 1 week prior to admission. A. hydrophila was isolated from a culture of purulent synovial fluid. Magnetic resonance imaging revealed profuse abscess collection between the right infraspinatus muscle and trapezius muscle and swelling of the right and left paraspinatus muscles, which suggested myositis-related dropped head syndrome. After surgery with arthrotomy, function of the shoulder and neck extensors was significantly improved.

  3. Drops can bounce from perfectly hydrophilic surfaces

    NASA Astrophysics Data System (ADS)

    Kolinski, J. M.; Mahadevan, L.; Rubinstein, S. M.

    2014-10-01

    Drops are well known to rebound from superhydrophobic surfaces and from liquid surfaces. Here, we show that drops can also rebound from a superhydrophilic solid surface such as an atomically smooth mica sheet. However, the coefficient of restitution CR associated with this process is significantly lower than that associated with rebound from superhydrophobic surfaces. A direct imaging method allows us to characterize the dynamics of the deformation of the drop in entering the vicinity of the surface. We find that drop bouncing occurs without the drop ever touching the solid and there is a nanometer-scale film of air that separates the liquid and solid, suggesting that shear in the air film is the dominant source of dissipation during rebound. Furthermore, we see that any discrete nanometer-height defects on an otherwise hydrophilic surface, such as treated glass, completely inhibits the bouncing of the drop, causing the liquid to wet the surface. Our study adds a new facet to the dynamics of droplet impact by emphasizing that the thin film of air can play a role not just in the context of splashing but also bouncing, while highlighting the role of rare surface defects in inhibiting this response.

  4. Transition Mode Shapes in a Vibrating Drop

    NASA Astrophysics Data System (ADS)

    Vukasinovic, Bojan; Smith, Marc K.; Glezer, Ari

    2000-11-01

    Vertical, time-periodic vibration of a diaphragm has been used to atomize a primary sessile drop into a fine spray of secondary droplets. The evolution and rate of atomization depend on the coupled dynamics of the sessile drop and the piezoelectrically-driven, low-mass diaphragm. The evolution of the free surface of the drop is characterized by the appearance of a hierarchy of surface waves that we investigated using high-speed imaging and laser vibrometry. At low-driving amplitudes, we see the appearance of time-harmonic axisymmetric waves on the drop's free surface induced by the motion of the contact line. As the vibration amplitude increases, azimuthal waves at the subharmonic of the forcing frequency appear around the periphery of the drop and propagate towards its center. A striking lattice mode emerges upon the breakdown of the axisymmetric wave pattern, followed by the appearance of the highly-agitated free surface of the pre-ejection mode shape. Subsequent to the breakdown of the lattice structure, the frequency of the most energetic mode is a subharmonic of the driving frequency. The complex interaction of the fundamental and subharmonic waves ultimately leads to the breakdown of the free surface and the atomization of the drop.

  5. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, M.; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Lauriie, S.; Garcia, K.; Sargsyan, A.; Martin, D.; Ribeiro, L.; Lui, J.; Macias, B.; Arbeille, P.; Danielson, R.; Chang, D.; Johnston, S.; Ploutz-Snyder, R.; Smith, S.

    2016-01-01

    NASA is focusing on long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low-Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but more than 50% of ISS astronauts experienced more profound, chronic changes with objective structural and functional findings such as papilledema and choroidal folds. Globe flattening, optic nerve sheath dilation, and optic nerve tortuosity also are apparent. This pattern is referred to as the visual impairment and intracranial pressure (VIIP) syndrome. VIIP signs and symptoms, as well as postflight lumbar puncture data, suggest that elevated intracranial pressure (ICP) may be associated with the spaceflight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration spaceflight, and to correlate these findings with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as the VIIP-related effects of those shifts, is predicted by the crewmember's preflight conditions and responses to acute hemodynamic manipulations (such as head-down tilt). Lastly, we will evaluate the patterns of fluid distribution in ISS astronauts during acute reversal of fluid shifts through application of lower body negative pressure (LBNP) interventions to characterize and explain general and individual responses. METHODS: We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the Figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, calcaneus tissue thickness (by

  6. Wellbore fluid

    SciTech Connect

    Dorsey, D.L.; Corley, W.T.

    1983-12-27

    A clay-based or clay-free aqueous thixotropic wellbore fluid having improved fluid loss control, desirable flow characteristics and low shale sensitivity for use in drilling a well comprising water or a brine base including an effective amount of an additive comprising a crosslinked potato starch, a heteropolysaccharide derived from a carbohydrate by bacteria of the genus Xanthomonas, and hydroxyethylcellulose or carboxymethylcellulose, is disclosed. This drilling fluid has been found to be nondamaging to the formations through which the well is drilled.

  7. Capillary migration of large confined super-hydrophobic drops in wedges

    NASA Astrophysics Data System (ADS)

    Torres, Logan; Weislogel, Mark; Arnold, Sam

    2016-11-01

    When confined within an interior corner, drops and bubbles migrate to regions of minimum energy by the combined effects of surface tension, surface wetting, and corner geometry. Such capillary phenomena are exploited for passive phase separation operations in micro-fluidic devices on earth and macro-fluidic devices aboard spacecraft. Our study focuses on the migration of large inertial-capillary drops confined between two planar super-hydrophobic surfaces. In our experiments, the near weightless environment of a drop tower produces Bo <<1 for drop volumes O(10mL) with migration velocities up to 10 cm/s. We observe transient power law behavior as a function of drop volume, wedge angle, initial confinement, and fluid properties including contact angle. We then further demonstrate how the experiment method may be employed as a large horizontal quiescent droplet generator for studies ranging from inertial non-wetting moving contact line investigations to large geyser-free horizontal drop impacts. NASA Cooperative Agreement NNX12AO47A, URMP.

  8. X-ray computed microtomography for drop shape analysis and contact angle measurement.

    PubMed

    Santini, Maurizio; Guilizzoni, Manfredo; Fest-Santini, Stephanie

    2013-11-01

    The interaction between an atomized fluid and a solid surface has a great importance in many fields, both in adiabatic conditions and when heat transfer is involved. To investigate the behavior of many drops in contact with a surface, the first step is to study a single one of them and in that, surface wettability is key parameter. Wettability analyses are usually performed by contact angle measurement, in most cases using the sessile drop or captive bubble techniques. Such techniques require optical acquisition of a side view of the drop or bubble, with a series of drawbacks when conventional optics are used, in particular for not uniform, not planar or rough base surfaces. X-ray micro-computed tomography is therefore used to acquire a 3D scan of a drop gently deposited on a surface, with the aim to reconstruct the drop surface and to perform contact angle measurements on true cross-sections of the drop-surface couple. Comparison with contact angle measurements performed on conventional images is performed. The results evidence that the proposed technique is very promising for surface characterization and to get more accurate and detailed information about wettability characteristics.

  9. Inertial modes of a periodically forced buoyant drop attached to a capillary

    NASA Astrophysics Data System (ADS)

    Chebel, Nicolas Abi; Risso, Frédéric; Masbernat, Olivier

    2011-10-01

    A drop of heptane attached to a capillary tip immersed in water is submitted to small amplitude volume oscillations. Its interface is imaged by means of a high-speed camera and its shape decomposed into spherical harmonics. The forcing frequency is varied over a large range including the frequencies of resonance of the three first modes of inertial shape oscillations. For a small drop, which remains almost spherical at rest, the geometrical constraint imposed by the attachment on the capillary tip causes the oscillation modes to be very different from those of a free drop. Surprisingly, the resonance of large drops is observed at the frequency predicted for a free, pure, and neutrally buoyant drop and mainly involves a single spherical harmonic; only the damping rate is observed to be moderately larger. Since it gives rise to oscillations close to this ideal case, the present experimental method could be used, complementary to quasi-static oscillation of a pendant drop, to investigate dynamic interfacial tension at high frequency of various fluid systems.

  10. Spreading of Electrolyte Drops on Charged Surfaces: Electric Double Layer Effects on Drop Dynamics

    NASA Astrophysics Data System (ADS)

    Bae, Kyeong; Sinha, Shayandev; Chen, Guang; Das, Siddhartha

    2015-11-01

    Drop spreading is one of the most fundamental topics of wetting. Here we study the spreading of electrolyte drops on charged surfaces. The electrolyte solution in contact with the charged solid triggers the formation of an electric double layer (EDL). We develop a theory to analyze how the EDL affects the drop spreading. The drop dynamics is studied by probing the EDL effects on the temporal evolution of the contact angle and the base radius (r). The EDL effects are found to hasten the spreading behaviour - this is commensurate to the EDL effects causing a ``philic'' tendency in the drops (i.e., drops attaining a contact angle smaller than its equilibrium value), as revealed by some of our recent papers. We also develop scaling laws to illustrate the manner in which the EDL effects make the r versus time (t) variation deviate from the well known r ~tn variation, thereby pinpointing the attainment of different EDL-mediated spreading regimes.

  11. Lifetime of oil drops pressed by buoyancy against a planar interface: large drops.

    PubMed

    Rojas, Clara; García-Sucre, Máximo; Urbina-Villalba, Germán

    2010-11-01

    In a previous report [C. Rojas, G. Urbina-Villalba, and M. García-Sucre, Phys. Rev. E 81, 016302 (2010)] it was shown that emulsion stability simulations are able to reproduce the lifetime of micrometer-size drops of hexadecane pressed by buoyancy against a planar water-hexadecane interface. It was confirmed that small drops (r(i)< 10 μm) stabilized with β -casein behave as nondeformable particles, moving with a combination of Stokes and Taylor tensors as they approach the interface. Here, a similar methodology is used to parametrize the potential of interaction of drops of soybean oil stabilized with bovine serum albumin. The potential obtained is then employed to study the lifetime of deformable drops in the range 10 ≤ r(i) ≤ 1000 μm . It is established that the average lifetime of these drops can be adequately replicated using the model of truncated spheres. However, the results depend sensibly on the expressions of the initial distance of deformation and the maximum film radius used in the calculations. The set of equations adequate for large drops is not satisfactory for medium-size drops (10 ≤ r(i) ≤ 100 μm) , and vice versa. In the case of large particles, the increase in the interfacial area as a consequence of the deformation of the drops generates a very large repulsive barrier which opposes coalescence. Nevertheless, the buoyancy force prevails. As a consequence, it is the hydrodynamic tensor of the drops which determine the characteristic behavior of the lifetime as a function of the particle size. While the average values of the coalescence time of the drops can be justified by the mechanism of film thinning, the scattering of the experimental data of large drops cannot be rationalized using the methodology previously described. A possible explanation of this phenomenon required elaborate simulations which combine deformable drops, capillary waves, repulsive interaction forces, and a time-dependent surfactant adsorption.

  12. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, M. B.; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Laurie, S.; Garcia, K.; Sargsyan, A.; Martin, D.; Lui, J.; Macias, B.; Arbeille, P.; Danielson, R.; Chang, D.; Gunga, H.; Johnston, S.; Westby, C.; Ribeiro, L.; Ploutz-Snyder, R.; Smith, S.

    2015-01-01

    INTRODUCTION: Mechanisms responsible for the ocular structural and functional changes that characterize the visual impairment and intracranial pressure (ICP) syndrome (VIIP) are unclear, but hypothesized to be secondary to the cephalad fluid shift experienced in spaceflight. This study will relate the fluid distribution and compartmentalization associated with long-duration spaceflight with VIIP symptoms. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as the VIIP-related effects of those shifts, can be predicted preflight with acute hemodynamic manipulations, and also if lower body negative pressure (LBNP) can reverse the VIIP effects. METHODS: Physiologic variables will be examined pre-, in- and post-flight in 10 International Space Station crewmembers including: fluid compartmentalization (D2O and NaBr dilution); interstitial tissue thickness (ultrasound); vascular dimensions and dynamics (ultrasound and MRI (including cerebrospinal fluid pulsatility)); ocular measures (optical coherence tomography, intraocular pressure, ultrasound); and ICP measures (tympanic membrane displacement, otoacoustic emissions). Pre- and post-flight measures will be assessed while upright, supine and during 15 deg head-down tilt (HDT). In-flight measures will occur early and late during 6 or 12 month missions. LBNP will be evaluated as a countermeasure during HDT and during spaceflight. RESULTS: The first two crewmembers are in the preflight testing phase. Preliminary results characterize the acute fluid shifts experienced from upright, to supine and HDT postures (increased stroke volume, jugular dimensions and measures of ICP) which are reversed with 25 millimeters Hg LBNP. DISCUSSION: Initial results indicate that acute cephalad fluid shifts may be related to VIIP symptoms, but also may be reversible by LBNP. The effect of a chronic fluid shift has yet to be evaluated. Learning Objectives: Current spaceflight VIIP research is described

  13. Electrorheological fluids

    SciTech Connect

    Halsey, T.C.; Martin, J.E.

    1993-10-01

    An electrorheological fluid is a substance whose form changes in the presence of electric fields. Depending on the strength of the field to which it is subjected, an electrorheological fluid can run freely like water, ooze like honey or solidify like gelatin. Indeed, the substance can switch from ne state to another within a few milliseconds. Electrorheological fluids are easy to make; they consist of microscopic particles suspended in an insulating liquid. Yet they are not ready for most commercial applications. They tend to suffer from a number of problems, including structural weakness as solids, abrasiveness as liquids and chemical breakdown, especially at high temperatures. Automotive engineers could imagine, for instance, constructing an electrorheological clutch. It was also hoped that electrorheological fluids would lead to valveless hydraulic systems, in which solidifying fluid would shut off flow through a thin section of pipe. Electrorheological fluids also offer the possibility of a shock absorber that provides response times of milliseconds and does not require mechanical adjustments. 3 refs.

  14. Stress Drops for Potentially Induced Earthquake Sequences

    NASA Astrophysics Data System (ADS)

    Huang, Y.; Beroza, G. C.; Ellsworth, W. L.

    2015-12-01

    Stress drop, the difference between shear stress acting across a fault before and after an earthquake, is a fundamental parameter of the earthquake source process and the generation of strong ground motions. Higher stress drops usually lead to more high-frequency ground motions. Hough [2014 and 2015] observed low intensities in "Did You Feel It?" data for injection-induced earthquakes, and interpreted them to be a result of low stress drops. It is also possible that the low recorded intensities could be a result of propagation effects. Atkinson et al. [2015] show that the shallow depth of injection-induced earthquakes can lead to a lack of high-frequency ground motion as well. We apply the spectral ratio method of Imanishi and Ellsworth [2006] to analyze stress drops of injection-induced earthquakes, using smaller earthquakes with similar waveforms as empirical Green's functions (eGfs). Both the effects of path and linear site response should be cancelled out through the spectral ratio analysis. We apply this technique to the Guy-Greenbrier earthquake sequence in central Arkansas. The earthquakes migrated along the Guy-Greenbrier Fault while nearby injection wells were operating in 2010-2011. Huang and Beroza [GRL, 2015] improved the magnitude of completeness to about -1 using template matching and found that the earthquakes deviated from Gutenberg-Richter statistics during the operation of nearby injection wells. We identify 49 clusters of highly similar events in the Huang and Beroza [2015] catalog and calculate stress drops using the source model described in Imanishi and Ellsworth [2006]. Our results suggest that stress drops of the Guy-Greenbrier sequence are similar to tectonic earthquakes at Parkfield, California (the attached figure). We will also present stress drop analysis of other suspected induced earthquake sequences using the same method.

  15. Acoustic levitation of liquid drops: Dynamics, manipulation and phase transitions.

    PubMed

    Zang, Duyang; Yu, Yinkai; Chen, Zhen; Li, Xiaoguang; Wu, Hongjing; Geng, Xingguo

    2017-03-18

    The technique of acoustic levitation normally produces a standing wave and the potential well of the sound field can be used to trap small objects. Since no solid surface is involved it has been widely applied for the study of fluid physics, nucleation, bio/chemical processes, and various forms of soft matter. In this article, we survey the works on drop dynamics in acoustic levitation, focus on how the dynamic behavior is related to the rheological properties and discuss the possibility to develop a novel rheometer based on this technique. We review the methods and applications of acoustic levitation for the manipulation of both liquid and solid samples and emphasize the important progress made in the study of phase transitions and bio-chemical analysis. We also highlight the possible open areas for future research.

  16. Drop Impingement on Highly Wetting Micro/Nano Porous Surfaces

    NASA Astrophysics Data System (ADS)

    Buie, Cullen; Joung, Youngsoo

    2011-11-01

    Recently, we developed a novel fabrication method using a combination of electrophoretic deposition (EPD) and break down anodization (BDA) to achieve highly wetting nanoporous surfaces with microscale features. In this study we investigate droplet impingement behavior on these surfaces as a function of impact velocity, droplet size, and liquid properties. We observe impingement modes we denote as ``necking'' (droplet breaks before full penetration in the porous surface), ``spreading'' (continuous wicking into the porous surface), and ``jetting'' (jets of liquid emanate from the edges of the wicking liquid). To predict the droplet impingement modes, we've developed a non-dimensional parameter that is a function of droplet velocity, dynamic viscosity, effective pore radius and contact angle. The novel dimensionless parameter successfully predicts drop impingement modes across multiple fluids. Results of this study will inform the design of spray impingement cooling systems for electronics applications where the ``spreading'' mode is preferred.

  17. Chemically driven fluid transport in long microchannels

    NASA Astrophysics Data System (ADS)

    Shen, Mingren; Ye, Fangfu; Liu, Rui; Chen, Ke; Yang, Mingcheng; Ripoll, Marisol

    2016-09-01

    Chemical gradients maintained along surfaces can drive fluid flows by diffusio-osmosis, which become significant at micro- and nano-scales. Here, by means of mesoscopic simulations, we show that a concentration drop across microchannels with periodically inhomogeneous boundary walls can laterally transport fluids over arbitrarily long distances along the microchannel. The driving field is the secondary local chemical gradient parallel to the channel induced by the periodic inhomogeneity of the channel wall. The flow velocity depends on the concentration drop across the channel and the structure and composition of the channel walls, but it is independent of the overall channel length. Our work thus presents new insight into the fluid transport in long microchannels commonly found in nature and is useful for designing novel micro- or nano-fluidic pumps.

  18. Electrohydrodynamic deformation of drops and bubbles at large Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Schnitzer, Ory

    2015-11-01

    In Taylor's theory of electrohydrodynamic drop deformation by a uniform electric field, inertia is neglected at the outset, resulting in fluid velocities that scale with E2, E being the applied-field magnitude. When considering strong fields and low viscosity fluids, the Reynolds number predicted by this scaling may actually become large, suggesting the need for a complementary large-Reynolds-number analysis. Balancing viscous and electrical stresses reveals that the velocity scales with E 4 / 3. Considering a gas bubble, the external flow is essentially confined to two boundary layers propagating from the poles to the equator, where they collide to form a radial jet. Remarkably, at leading order in the Capillary number the unique scaling allows through application of integral mass and momentum balances to obtain a closed-form expression for the O (E2) bubble deformation. Owing to a concentrated pressure load at the vicinity of the collision region, the deformed profile features an equatorial dimple which is non-smooth on the bubble scale. The dynamical importance of internal circulation in the case of a liquid drop leads to an essentially different deformation mechanism. This is because the external boundary layer velocity attenuates at a short distance from the interface, while the internal boundary-layer matches with a Prandtl-Batchelor (PB) rotational core. The dynamic pressure associated with the internal circulation dominates the interfacial stress profile, leading to an O (E 8 / 3) deformation. The leading-order deformation can be readily determined, up to the PB constant, without solving the circulating boundary-layer problem. To encourage attempts to verify this new scaling, we shall suggest a favourable experimental setup in which inertia is dominant, while finite-deformation, surface-charge advection, and gravity effects are negligible.

  19. Fluid Management System (FMS) fluid systems overview

    NASA Technical Reports Server (NTRS)

    Baird, R. S.

    1990-01-01

    Viewgraphs on fluid management system (FMS) fluid systems overview are presented. Topics addressed include: fluid management system description including system requirements (integrated nitrogen system, integrated water system, and integrated waste gas system) and physical description; and fluid management system evolution.

  20. Drop deployment system for crystal growth apparatus

    NASA Technical Reports Server (NTRS)

    Rhodes, Percy H. (Inventor); Snyder, Robert S. (Inventor); Pusey, Marc L. (Inventor)

    1992-01-01

    This invention relates to a crystal growth apparatus (10) generally used for growing protein crystals wherein a vapor diffusion method is used for growing the crystals. In this apparatus, a precipitating solution and a solution containing dissolved crystalline material are stored in separate vials (12, 14), each having a resilient diaphragm (28) across one end and an opening (24) with a puncturable septum (26) thereacross at an opposite end. The vials are placed in receptacles (30) having a manifold (41) with a manifold diaphragm (42) in contact with the vial diaphragm at one end of the receptacle and a hollow needle (36) for puncturing the septum at the other end of the manifold. The needles of each vial communicate with a ball mixer (40) that mixes the precipitate and protein solutions and directs the mixed solution to a drop support (64) disposed in a crystal growth chamber (16), the drop support being a tube with an inner bevelled surface (66) that provides more support for the drop (68) than the tubes of the prior art. A sealable storage region (70) intermediate the drop support and mixer provides storage of the drop (68) and the grown crystals.

  1. Drops with non-circular footprints

    NASA Astrophysics Data System (ADS)

    Ravazzoli, Pablo D.; González, Alejandro G.; Diez, Javier A.

    2016-04-01

    In this paper we study the morphology of drops formed on partially wetting substrates, whose footprint is not circular. These drops are consequence of the breakup processes occurring in thin films when anisotropic contact line motions take place. The anisotropy is basically due to the hysteresis of the contact angle since there is a wetting process in some parts of the contact line, while a dewetting occurs in other parts. Here, we obtain a characteristic drop shape from the rupture of a long liquid filament sitting on a solid substrate. We analyze its shape and contact angles by means of goniometric and refractive techniques. We also find a non-trivial steady state solution for the drop shape within the long wave approximation (lubrication theory), and we compare most of its features with experimental data. This solution is presented both in Cartesian and polar coordinates, whose constants must be determined by a certain group of measured parameters. Besides, we obtain the dynamics of the drop generation from numerical simulations of the full Navier-Stokes equation, where we emulate the hysteretic effects with an appropriate spatial distribution of the static contact angle over the substrate.

  2. Bubble and Drop Nonlinear Dynamics (BDND)

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.; Leal, L. Gary; Thomas, D. A.; Crouch, R. K.

    1998-01-01

    Free drops and bubbles are weakly nonlinear mechanical systems that are relatively simple to characterize experimentally in 1-G as well as in microgravity. The understanding of the details of their motion contributes to the fundamental study of nonlinear phenomena and to the measurement of the thermophysical properties of freely levitated melts. The goal of this Glovebox-based experimental investigation is the low-gravity assessment of the capabilities of a modular apparatus based on ultrasonic resonators and on the pseudo- extinction optical method. The required experimental task is the accurate measurements of the large-amplitude dynamics of free drops and bubbles in the absence of large biasing influences such as gravity and levitation fields. A single-axis levitator used for the positioning of drops in air, and an ultrasonic water-filled resonator for the trapping of air bubbles have been evaluated in low-gravity and in 1-G. The basic feasibility of drop positioning and shape oscillations measurements has been verified by using a laptop-interfaced automated data acquisition and the optical extinction technique. The major purpose of the investigation was to identify the salient technical issues associated with the development of a full-scale Microgravity experiment on single drop and bubble dynamics.

  3. Drop Testing Representative Multi-Canister Overpacks

    SciTech Connect

    Snow, Spencer D.; Morton, Dana K.

    2015-06-01

    The objective of the work reported herein was to determine the ability of the Multi- Canister Overpack (MCO) canister design to maintain its containment boundary after an accidental drop event. Two test MCO canisters were assembled at Hanford, prepared for testing at the Idaho National Engineering and Environmental Laboratory (INEEL), drop tested at Sandia National Laboratories, and evaluated back at the INEEL. In addition to the actual testing efforts, finite element plastic analysis techniques were used to make both pre-test and post-test predictions of the test MCOs structural deformations. The completed effort has demonstrated that the canister design is capable of maintaining a 50 psig pressure boundary after drop testing. Based on helium leak testing methods, one test MCO was determined to have a leakage rate not greater than 1x10-5 std cc/sec (prior internal helium presence prevented a more rigorous test) and the remaining test MCO had a measured leakage rate less than 1x10-7 std cc/sec (i.e., a leaktight containment) after the drop test. The effort has also demonstrated the capability of finite element methods using plastic analysis techniques to accurately predict the structural deformations of canisters subjected to an accidental drop event.

  4. Drop splash on a smooth, dry surface

    NASA Astrophysics Data System (ADS)

    Riboux, Guillaume; Gordillo, Jose Manuel; Korobkin, Alexander

    2013-11-01

    It is our purpose here to determine the conditions under which a drop of a given liquid with a known radius R impacting against a smooth impermeable surface at a velocity V, will either spread axisymmetrically onto the substrate or will create a splash, giving rise to usually undesired star-shaped patterns. In our experimental setup, drops are generated injecting low viscosity liquids falling under the action of gravity from a stainless steel hypodermic needle. The experimental observations using two high speed cameras operating simultaneously and placed perpendicularly to each other reveal that, initially, the drop deforms axisymmetrically, with A (T) the radius of the wetted area. For high enough values of the drop impact velocity, a thin sheet of liquid starts to be ejected from A (T) at a velocity Vjet > V for instants of time such that T >=Tc . If Vjet is above a certain threshold, which depends on the solid wetting properties as well as on the material properties of both the liquid and the atmospheric gas, the rim of the lamella dewets the solid to finally break into drops. Using Wagner's theory we demonstrate that A (T) =√{ 3 RVT } and our results also reveal that Tc We - 1 / 2 =(ρV2 R / σ) - 1 / 2 and Vjet We 1 / 4 .

  5. Drop impact on inclined superhydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Choi, Wonjae; Leclear, Sani; Leclear, Johnathon; Abhijeet, .; Park, Kyoo-Chul

    We report an empirical study and dimensional analysis on the impact patterns of water drops on inclined superhydrophobic surfaces. While the classic Weber number determines the spreading and recoiling dynamics of a water drop on a horizontal / smooth surface, for a superhydrophobic surface, the dynamics depends on two distinct Weber numbers, each calculated using the length scale of the drop or of the pores on the surface. Impact on an inclined superhydrophobic surface is even more complicated, as the velocity that determines the Weber number is not necessarily the absolute speed of the drop but the velocity components normal and tangential to the surface. We define six different Weber numbers, using three different velocities (absolute, normal and tangential velocities) and two different length scales (size of the drop and of the texture). We investigate the impact patterns on inclined superhydrophobic surfaces with three different types of surface texture: (i) posts, (ii) ridges aligned with and (iii) ridges perpendicular to the impact direction. Results suggest that all six Weber numbers matter, but affect different parts of the impact dynamics, ranging from the Cassie-Wenzel transition, maximum spreading, to anisotropic deformation. We acknowledge financial support from the Office of Naval Research (ONR) through Contract 3002453812.

  6. Fluid Mechanics Optimising Organic Synthesis

    NASA Astrophysics Data System (ADS)

    Leivadarou, Evgenia; Dalziel, Stuart

    2015-11-01

    The Vortex Fluidic Device (VFD) is a new ``green'' approach in the synthesis of organic chemicals with many industrial applications in biodiesel generation, cosmetics, protein folding and pharmaceutical production. The VFD is a rapidly rotating tube that can operate with a jet feeding drops of liquid reactants to the base of the tube. The aim of this project is to explain the fluid mechanics of the VFD that influence the rate of reactions. The reaction rate is intimately related to the intense shearing that promotes collision between reactant molecules. In the VFD, the highest shears are found at the bottom of the tube in the Rayleigh and the Ekman layer and at the walls in the Stewardson layers. As a step towards optimising the performance of the VFD we present experiments conducted in order to establish the minimum drop volume and maximum rotation rate for maximum axisymmetric spreading without fingering instability. PhD candidate, Department of Applied Mathematics and Theoretical Physics.

  7. Sample handling and chemical kinetics in an acoustically levitated drop microreactor.

    PubMed

    Pierre, Zakiah N; Field, Christopher R; Scheeline, Alexander

    2009-10-15

    Accurate measurement of enzyme kinetics is an essential part of understanding the mechanisms of biochemical reactions. The typical means of studying such systems use stirred cuvettes, stopped-flow apparatus, microfluidic systems, or other small sample containers. These methods may prove to be problematic if reactants or products adsorb to or react with the container's surface. As an alternative approach, we have developed an acoustically-levitated drop reactor eventually intended to study enzyme-catalyzed reaction kinetics related to free radical and oxidative stress chemistry. Microliter-scale droplet generation, reactant introduction, maintenance, and fluid removal are all important aspects in conducting reactions in a levitated drop. A three capillary bundle system has been developed to address these needs. We report kinetic measurements for both luminol chemiluminescence and the reaction of pyruvate with nicotinamide adenine dinucleotide, catalyzed by lactate dehydrogenase, to demonstrate the feasibility of using a levitated drop in conjunction with the developed capillary sample handling system as a microreactor.

  8. Interactions Forces and the Flow-Induced Coalescence of Drops and Bubbles

    NASA Technical Reports Server (NTRS)

    Leal, L. Gary; Israelachvili, J.

    2004-01-01

    In order to accomplish the proposed macroscale experimental goals, we designed and built a pair of miniaturized computer-controlled four-roll mills, similar but much smaller than the 4-roll mill that had been develop earlier in Prof. Leal's group for studies of drop deformation and breakup. This unique experimental facility allows for controlled experiments on the breakup and coalescence of very small drops in the size range of 20-200 micrometers in diameter for a wide variety of flows and under a wide range of flow conditions including time-dependent flows, etc. The small size of this device is necessary for coalescence studies, since coalescence occurs in viscous fluids at capillary numbers that are large enough to be experimentally accessible only for drops that are smaller than approximately 100_m in diameter. Using these miniaturized 4-roll mills, we have obtained the first quantitative data (so far as we are aware) on the flow-induced coalescence process.

  9. A theory of wall-induced lateral migration of a drop in shear: effects of drop inclination and viscoelasticity

    NASA Astrophysics Data System (ADS)

    Sarkar, Kausik

    2012-11-01

    Recently, migration of suspended particles, drops, polymers and biological cells have assumed importance in microfluidic separation and filtration assays. A rigid sphere in shear does not move cross-stream due to the reversibility in a Stokes flow. Deformation, as well as inertia and viscoelasticity, breaks the reversibility and leads to lateral migration away from a nearby wall. There have been algebraically complex perturbative analyses of the moving boundary problem [e.g. Chan and Leal 1979, JFM 92,131] to determine the migration velocity. However, the underlying physics remains unclear. Here, we show that the migration is induced by the image stresslet field, as was also indicated earlier by Smart and Leighton [1991, Phys. Fluid A, 3, 21]. We relate the stresslet field to the Interface tensor, and investigate the effects of drop inclination. In contrast to a plausible notion asserted also in the literature, that reduced inclination (increased alignment with flow) decreases migration, it is shown here that reduced inclination increases the stresslet and thereby the migration velocity. A semi-analytical expression of migration velocity based on numerically computed stresslet will be compared against simulation and the results will be discussed. Partially supported by NSF.

  10. The surface temperature of free evaporating drops

    NASA Astrophysics Data System (ADS)

    Borodulin, V. Y.; Letushko, V. N.; Nizovtsev, M. I.; Sterlyagov, A. N.

    2016-10-01

    Complex experimental and theoretical investigation of heat and mass transfer processes was performed at evaporation of free liquid drops. For theoretical calculation the emission-diffusion model was proposed. This allowed taking into account the characteristics of evaporation of small droplets, for which heat and mass transfer processes are not described in the conventional diffusion model. The calculation results of evaporation of droplets of different sizes were compared using two models: the conventional diffusion and emission-diffusion models. To verify the proposed physical model, the evaporation of droplets suspended on a polypropylene fiber was experimentally investigated. The form of droplets in the evaporation process was determined using microphotographing. The temperature was measured on the surfaces of evaporating drops using infrared thermography. The experimental results have showed good agreement with the numerical data for the time of evaporation and the temperature of evaporating drops.

  11. Contact line arrest in solidifying spreading drops

    NASA Astrophysics Data System (ADS)

    de Ruiter, Rielle; Colinet, Pierre; Snoeijer, Jacco; Gelderblom, Hanneke

    2016-11-01

    When does a drop, deposited on a cold substrate, stop spreading? Despite the practical relevance of this question, for example in airplane icing and 3D metal printing, the exact mechanism of arrest in solidifying spreading drops has not yet been unraveled. Here, we consider the spreading and arrest of hexadecane drops of constant volume on two smooth wettable substrates; copper with a high thermal conductivity and glass with a low thermal conductivity. We record the spreading radius and contact angle in time for a range of substrate temperatures. We show that our measurements on both copper and glass are well explained by a contact line arrest condition based on crystallization kinetics, which takes into account the effect of kinetic undercooling and the thermal conductivity of the substrate.

  12. Dropping In a Microgravity Environment (DIME) contest

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The first NASA Dropping In a Microgravity Environment (DIME) student competition pilot project came to a conclusion at the Glenn Research Center in April 2001. The competition involved high-school student teams who developed the concept for a microgravity experiment and prepared an experiment proposal. The two student teams - COSI Academy, sponsored by the Columbus Center of Science and Industry, and another team from Cincinnati, Ohio's Sycamore High School, designed a microgravity experiment, fabricated the experimental apparatus, and visited NASA Glenn to operate their experiment in the 2.2 Second Drop Tower. Here Jose Carrion, a lab mechanic with AKAC, starts the orange-colored drag shield, and the experiment apparatus inside, on the hoist upward to the control station at the top of the drop tower. This image is from a digital still camera; higher resolution is not available.

  13. Dropped head syndrome and Systemic sclerosis.

    PubMed

    Rosato, Edoardo; Rossi, Carmelina; Salsano, Felice

    2009-05-01

    The prominent or isolated weakness of cervical extensor muscles is a relatively rare clinical sign. Commonly, this is known as "dropped-head syndrome". This abnormal flexion of the head may occur in a variety of neuromuscular diseases and in a few non-neurological disorders as well. Systemic sclerosis is a clinically heterogeneous disorder which affects small arteries, microvessels and connective tissue with the involvement of multiple organs such as lung, heart, kidney and gastrointestinal tract. There is no evidence in literature of association between dropped head syndrome and rheumatic diseases, particularly systemic sclerosis. The case we describe concerns a 74-year-old woman with dropped-head syndrome associated to Systemic sclerosis and pulmonary hypertension in absence of myositis signs.

  14. Secondary breakup of coal water slurry drops

    NASA Astrophysics Data System (ADS)

    Zhao, Hui; Liu, Hai-Feng; Xu, Jian-Liang; Li, Wei-Feng

    2011-11-01

    To investigate secondary atomization of coal water slurry (CWS), deformation and breakup of eight kinds of CWS drops are presented using high speed digital camera. Based on morphology, deformation and breakup regimes of CWS drops can be termed some different modes: deformation, multimode breakup (including two sub-modes: hole breakup and tensile breakup), and shear breakup. Correlations on the ranges of breakup modes are also obtained. The conventional Weber number and Ohnesorge number are found to be insufficient to classify all breakup modes of CWS drops, so two other non-dimensional numbers based on rheology of CWS are suggested to use in the deformation and breakup regime map. Finally, total breakup time is studied and correlated, which increases with Ohnesorge number.

  15. Micro coulometric titration in a liquid drop.

    PubMed

    Kanyanee, Tinakorn; Fuekhad, Pongwasin; Grudpan, Kate

    2013-10-15

    Miniaturized coulometric titration in a liquid drop has been investigated. Assays of ascorbic acid and thiosulfate with iodine titration were chosen as models. Constant volumes of falling liquid drops containing sample or reagent are manipulated via gravimetrical force to move along a slope hydrophobic path and directed to stop or to move out from an electrode. Such manipulation is useful for delivery of sample and reagents, in a way of flow without tubing. Electrochemical generation of titrant, in this case, iodine, is started at the electrode and micro coulometric titration can be performed in a drop by applying constant current. Timing in the titration can be made via naked eye with a stopwatch or via recording with a webcam camera connecting to a computer to detect the change due to the blue color complex of the excess iodine and starch.

  16. Profiles of electrified drops and bubbles

    NASA Technical Reports Server (NTRS)

    Basaran, O. A.; Scriven, L. E.

    1982-01-01

    Axisymmetric equilibrium shapes of conducting drops and bubbles, (1) pendant or sessile on one face of a circular parallel-plate capacitor or (2) free and surface-charged, are found by solving simultaneously the free boundary problem consisting of the augmented Young-Laplace equation for surface shape and the Laplace equation for electrostatic field, given the surface potential. The problem is nonlinear and the method is a finite element algorithm employing Newton iteration, a modified frontal solver, and triangular as well as quadrilateral tessellations of the domain exterior to the drop in order to facilitate refined analysis of sharply curved drop tips seen in experiments. The stability limit predicted by this computer-aided theoretical analysis agrees well with experiments.

  17. Thermocapillary Convection in Bubbles and Drops

    NASA Technical Reports Server (NTRS)

    Balassubramaniam; Subramanian, R. Shankar

    2003-01-01

    When bubbles or drops are present in an immiscible liquid in reduced gravity and the temperature of the liquid is non-uniform, a thermocapillary stress is generated at the interface due to the variation of interfacial tension with temperature. The resulting flow propels the drop freely suspended in the liquid towards warmer regions, so as to minimize the interfacial energy. In this presentation, we will focus on the effect of convective transport of momentum and energy, that are characterized by the Reynolds number and the Marangoni number, respectively. The results of asymptotic analyses for the speed of the drop for low and large values of these parameters will be discussed. These predictions as well as those from numerical simulations will be compared with reduced gravity experimental results obtained from experiments performed aboard the space shuttle.

  18. Nonreciprocal photonic crystal add-drop filter

    SciTech Connect

    Tao, Keyu; Xiao, Jun-Jun; Yin, Xiaobo

    2014-11-24

    We present a versatile add-drop integrated photonic filter (ADF) consisting of nonreciprocal waveguides in which the propagation of light is restricted in one predetermined direction. With the bus and add/drop waveguides symmetrically coupled through a cavity, the four-port device allows each individual port to add and/or drop a signal of the same frequency. The scheme is general and we demonstrate the nonreciprocal ADF with magneto-optical photonic crystals. The filter is immune to waveguide defects, allowing straightforward implementation of multi-channel ADFs by cascading the four-port designs. The results should find applications in wavelength-division multiplexing and related integrated photonic techniques.

  19. Effects of rod worth and drop speed on the BWR off-center rod drop accident

    SciTech Connect

    Cokinos, D.M.; Carew, J.F.

    1985-01-01

    BWR off-center RDA calculations have been performed for selected rod worths and drop speeds. While in all cases the peak fuel enthalpy was well below the 280 cal/g fuel criterion, a substantial sensitivity to control rod worth and rod drop speed was observed.

  20. Computer simulations of nematic drops: Coupling between drop shape and nematic order

    NASA Astrophysics Data System (ADS)

    Rull, L. F.; Romero-Enrique, J. M.; Fernandez-Nieves, A.

    2012-07-01

    We perform Monte Carlo computer simulations of nematic drops in equilibrium with their vapor using a Gay-Berne interaction between the rod-like molecules. To generate the drops, we initially perform NPT simulations close to the nematic-vapor coexistence region, allow the system to equilibrate and subsequently induce a sudden volume expansion, followed with NVT simulations. The resultant drops coexist with their vapor and are generally not spherical but elongated, have the rod-like particles tangentially aligned at the surface and an overall nematic orientation along the main axis of the drop. We find that the drop eccentricity increases with increasing molecular elongation, κ. For small κ the nematic texture in the drop is bipolar with two surface defects, or boojums, maximizing their distance along this same axis. For sufficiently high κ, the shape of the drop becomes singular in the vicinity of the defects, and there is a crossover to an almost homogeneous texture; this reflects a transition from a spheroidal to a spindle-like drop.

  1. Smoothed particle hydrodynamics simulations of evaporation and explosive boiling of liquid drops in microgravity.

    PubMed

    Sigalotti, Leonardo Di G; Troconis, Jorge; Sira, Eloy; Peña-Polo, Franklin; Klapp, Jaime

    2015-07-01

    The rapid evaporation and explosive boiling of a van der Waals (vdW) liquid drop in microgravity is simulated numerically in two-space dimensions using the method of smoothed particle hydrodynamics. The numerical approach is fully adaptive and incorporates the effects of surface tension, latent heat, mass transfer across the interface, and liquid-vapor interface dynamics. Thermocapillary forces are modeled by coupling the hydrodynamics to a diffuse-interface description of the liquid-vapor interface. The models start from a nonequilibrium square-shaped liquid of varying density and temperature. For a fixed density, the drop temperature is increased gradually to predict the point separating normal boiling at subcritical heating from explosive boiling at the superheat limit for this vdW fluid. At subcritical heating, spontaneous evaporation produces stable drops floating in a vapor atmosphere, while at near-critical heating, a bubble is nucleated inside the drop, which then collapses upon itself, leaving a smaller equilibrated drop embedded in its own vapor. At the superheat limit, unstable bubble growth leads to either fragmentation or violent disruption of the liquid layer into small secondary drops, depending on the liquid density. At higher superheats, explosive boiling occurs for all densities. The experimentally observed wrinkling of the bubble surface driven by rapid evaporation followed by a Rayleigh-Taylor instability of the thin liquid layer and the linear growth of the bubble radius with time are reproduced by the simulations. The predicted superheat limit (T(s)≈0.96) is close to the theoretically derived value of T(s)=1 at zero ambient pressure for this vdW fluid.

  2. Smoothed particle hydrodynamics simulations of evaporation and explosive boiling of liquid drops in microgravity

    NASA Astrophysics Data System (ADS)

    Sigalotti, Leonardo Di G.; Troconis, Jorge; Sira, Eloy; Peña-Polo, Franklin; Klapp, Jaime

    2015-07-01

    The rapid evaporation and explosive boiling of a van der Waals (vdW) liquid drop in microgravity is simulated numerically in two-space dimensions using the method of smoothed particle hydrodynamics. The numerical approach is fully adaptive and incorporates the effects of surface tension, latent heat, mass transfer across the interface, and liquid-vapor interface dynamics. Thermocapillary forces are modeled by coupling the hydrodynamics to a diffuse-interface description of the liquid-vapor interface. The models start from a nonequilibrium square-shaped liquid of varying density and temperature. For a fixed density, the drop temperature is increased gradually to predict the point separating normal boiling at subcritical heating from explosive boiling at the superheat limit for this vdW fluid. At subcritical heating, spontaneous evaporation produces stable drops floating in a vapor atmosphere, while at near-critical heating, a bubble is nucleated inside the drop, which then collapses upon itself, leaving a smaller equilibrated drop embedded in its own vapor. At the superheat limit, unstable bubble growth leads to either fragmentation or violent disruption of the liquid layer into small secondary drops, depending on the liquid density. At higher superheats, explosive boiling occurs for all densities. The experimentally observed wrinkling of the bubble surface driven by rapid evaporation followed by a Rayleigh-Taylor instability of the thin liquid layer and the linear growth of the bubble radius with time are reproduced by the simulations. The predicted superheat limit (Ts≈0.96 ) is close to the theoretically derived value of Ts=1 at zero ambient pressure for this vdW fluid.

  3. Fundamental Drop Dynamics and Mass Transfer Experiments to Support Solvent Extraction Modeling Efforts

    SciTech Connect

    Kristi Christensen; Veronica Rutledge; Troy Garn

    2011-09-01

    In support of the Nuclear Energy Advanced Modeling Simulation Safeguards and Separations (NEAMS SafeSep) program, the Idaho National Laboratory (INL) worked in collaboration with Los Alamos National Laboratory (LANL) to further a modeling effort designed to predict mass transfer behavior for selected metal species between individual dispersed drops and a continuous phase in a two phase liquid-liquid extraction (LLE) system. The purpose of the model is to understand the fundamental processes of mass transfer that occur at the drop interface. This fundamental understanding can be extended to support modeling of larger LLE equipment such as mixer settlers, pulse columns, and centrifugal contactors. The work performed at the INL involved gathering the necessary experimental data to support the modeling effort. A custom experimental apparatus was designed and built for performing drop contact experiments to measure mass transfer coefficients as a function of contact time. A high speed digital camera was used in conjunction with the apparatus to measure size, shape, and velocity of the drops. In addition to drop data, the physical properties of the experimental fluids were measured to be used as input data for the model. Physical properties measurements included density, viscosity, surface tension and interfacial tension. Additionally, self diffusion coefficients for the selected metal species in each experimental solution were measured, and the distribution coefficient for the metal partitioning between phases was determined. At the completion of this work, the INL has determined the mass transfer coefficient and a velocity profile for drops rising by buoyancy through a continuous medium under a specific set of experimental conditions. Additionally, a complete set of experimentally determined fluid properties has been obtained. All data will be provided to LANL to support the modeling effort.

  4. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, Michael; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Sargsyan, A.; Martin, D.; Lui, J.; Macias, B.; Arbeille, P.; Platts, S.

    2014-01-01

    NASA is focusing on long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but more than 30% of ISS astronauts experience more profound, chronic changes with objective structural and functional findings such as papilledema and choroidal folds. Globe flattening, optic nerve sheath dilation, and optic nerve tortuosity also are apparent. This pattern is referred to as the visual impairment and intracranial pressure (VIIP) syndrome. VIIP signs and symptoms, as well as postflight lumbar puncture data, suggest that elevated intracranial pressure (ICP) may be associated with the space flight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration space flight, and to correlate these findings with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during space flight, as well as the VIIP-related effects of those shifts, is predicted by the crewmember's pre-flight condition and responses to acute hemodynamic manipulations (such as head-down tilt). Lastly, we will evaluate the patterns of fluid distribution in ISS astronauts during acute reversal of fluid shifts through application of lower body negative pressure (LBNP) interventions to characterize and explain general and individual responses. We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the Figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, calcaneus tissue thickness (by ultrasound

  5. Water drops dancing on ice: how sublimation leads to drop rebound.

    PubMed

    Antonini, C; Bernagozzi, I; Jung, S; Poulikakos, D; Marengo, M

    2013-07-05

    Drop rebound is a spectacular event that appears after impact on hydrophobic or superhydrophobic surfaces but can also be induced through the so-called Leidenfrost effect. Here we demonstrate that drop rebound can also originate from another physical phenomenon, the solid substrate sublimation. Through drop impact experiments on a superhydrophobic surface, a hot plate, and solid carbon dioxide (commonly known as dry ice), we compare drop rebound based on three different physical mechanisms, which apparently share nothing in common (superhydrophobicity, evaporation, and sublimation), but lead to the same rebound phenomenon in an extremely wide temperature range, from 300 °C down to even below -79 °C. The formation and unprecedented visualization of an air vortex ring around an impacting drop are also reported.

  6. Development of revolving drop surface tensiometer.

    PubMed

    Mitani, S; Sakai, K

    2012-01-01

    A revolving drop surface tensiometer, which measures the surface tension of a small amount of liquid, is proposed. A remarkable feature of this device is that while using the pendant drop method, it employs a centrifugal force to deform the liquid droplet. The centrifugal force induces a large distortion of the droplet, which enables an accurate measurement of the surface tension to be made. In our experimental setup, the centrifugal force can be increased so that the apparent acceleration becomes up to 100 times larger than that due to gravity, and the capability of this method to measure surface tensions was demonstrated with ethylene glycol.

  7. The new Drop Tower catapult system

    NASA Astrophysics Data System (ADS)

    von Kampen, Peter; Kaczmarczik, Ulrich; Rath, Hans J.

    2006-07-01

    The Center of Applied Space Technology and Microgravity (ZARM) was founded in 1985 as an institute of the University Bremen, which focuses on research on gravitational and space-related phenomena. In 1988, the construction of the "Drop Tower" began. Since then, the eye-catching tower with a height of 146 m and its characteristic glass roof has become the emblem of the technology centre in Bremen. The Drop Tower Bremen provides a facility for experiments under conditions of weightlessness. Items are considered weightless, when they are in "free fall", i.e. moving without propulsion within the gravity field of the earth. The height of the tower limits the simple "free fall" experiment period to max. 4.74 s. With the inauguration of the catapult system in December 2004, the ZARM is entering a new dimension. This world novelty will meet scientists' demands of extending the experiment period up to 9.5 s. Since turning the first sod on May 3rd, 1988, the later installation of the catapult system has been taken into account by building the necessary chamber under the tower. The catapult system is located in a chamber 10 m below the base of the tower. This chamber is almost completely occupied by 12 huge pressure tanks. These tanks are placed around the elongation of the vacuum chamber of the drop tube. In its centre there is the pneumatic piston that accelerates the drop capsule by the pressure difference between the vacuum inside the drop tube and the pressure inside the tanks. The acceleration level is adjusted by means of a servo hydraulic breaking system controlling the piston velocity. After only a quarter of a second the drop capsule achieves its lift-off speed of 175 km/h. With this exact speed, the capsule will rise up to the top of the tower and afterwards fall down again into the deceleration unit which has been moved under the drop tube in the meantime. The scientific advantages of the doubled experiment time are obvious: during almost 10 s of high

  8. Transformation of the bridge during drop separation

    NASA Astrophysics Data System (ADS)

    Chashechkin, Yu. D.; Prokhorov, V. E.

    2016-05-01

    The geometry of flows during separation of pendant drops of liquids with significantly different physical properties (alcohol, water, glycerin, oil) has been studied by high-speed video recording. The dynamics of the processes involving the formation of bridges of two characteristic shapes—slightly nonuniform in thickness and with thinning of the upper and lower ends—has been investigated. It has been shown that the shape change of the separated bridge has a number of stages determined by the properties of the liquid. As a result, the bridge is transformed into a small drop—a satellite drop.

  9. Millikan "oil drop" stabilized by growth.

    PubMed

    Sun, L K; Gertler, A W; Reiss, H

    1979-01-26

    A diffusion cloud chamber has been used to qualitatively study some dynamic properties of liquid drops by suspending them in an electric field at the plane of saturation (p/ps = 1, where p is the actual partial pressure of the vapor at a given elevation and ps is the equilibrium pressure at that temperature characteristic of that elevation). By varying the strength of the electric field, it is possible to change the size of the suspended droplets and even, if desired, to isolate a single drop.

  10. Electrohydrodynamic removal of particles from drop surfaces

    NASA Astrophysics Data System (ADS)

    Nudurupati, S.; Janjua, M.; Singh, P.; Aubry, N.

    2009-07-01

    A uniform electric field is used for cleaning drops of the particles they often carry on their surface. In a first step, particles migrate to either the drop’s poles or equator. This is due to the presence of an electrostatic force for which an analytical expression is derived. In a second step, particles concentrated near the poles are released into the ambient liquid via tip streaming, and those near the equator are removed by stretching the drop and breaking it into several droplets. In the latter case, particles are all concentrated in a small middle daughter droplet.

  11. Capillary flow as the cause of ring stains from dried liquid drops

    NASA Astrophysics Data System (ADS)

    Deegan, Robert D.; Bakajin, Olgica; Dupont, Todd F.; Huber, Greb; Nagel, Sidney R.; Witten, Thomas A.

    1997-10-01

    When a spilled drop of coffee dries on a solid surface, it leaves a dense, ring-like deposit along the perimeter (Fig. 1a). The coffee-initially dispersed over the entire drop-becomes concentrated into a tiny fraction of it. Such ring deposits are common wherever drops containing dispersed solids evaporate on a surface, and they influence processes such as printing, washing and coating. Ring deposits also provide a potential means to write or deposit a fine pattern onto a surface. Here we ascribe the characteristic pattern of the deposition to a form of capillary flow in which pinning of the contact line of the drying drop ensures that liquid evaporating from the edge is replenished by liquid from the interior. The resulting outward flow can carry virtually all the dispersed material to the edge. This mechanism predicts a distinctive power-law growth of the ring mass with time-a law independent of the particular substrate, carrier fluid or deposited solids. We have verified this law by microscopic observations of colloidal fluids.

  12. Diffuse-interface modeling of liquid-vapor coexistence in equilibrium drops using smoothed particle hydrodynamics.

    PubMed

    Sigalotti, Leonardo Di G; Troconis, Jorge; Sira, Eloy; Peña-Polo, Franklin; Klapp, Jaime

    2014-07-01

    We study numerically liquid-vapor phase separation in two-dimensional, nonisothermal, van der Waals (vdW) liquid drops using the method of smoothed particle hydrodynamics (SPH). In contrast to previous SPH simulations of drop formation, our approach is fully adaptive and follows the diffuse-interface model for a single-component fluid, where a reversible, capillary (Korteweg) force is added to the equations of motion to model the rapid but smooth transition of physical quantities through the interface separating the bulk phases. Surface tension arises naturally from the cohesive part of the vdW equation of state and the capillary forces. The drop models all start from a square-shaped liquid and spinodal decomposition is investigated for a range of initial densities and temperatures. The simulations predict the formation of stable, subcritical liquid drops with a vapor atmosphere, with the densities and temperatures of coexisting liquid and vapor in the vdW phase diagram closely matching the binodal curve. We find that the values of surface tension, as determined from the Young-Laplace equation, are in good agreement with the results of independent numerical simulations and experimental data. The models also predict the increase of the vapor pressure with temperature and the fitting to the numerical data reproduces very well the Clausius-Clapeyron relation, thus allowing for the calculation of the vaporization pressure for this vdW fluid.

  13. Numerical simulation of drop deformations and breakup modes caused by direct current electric fields

    NASA Astrophysics Data System (ADS)

    Paknemat, H.; Pishevar, A. R.; Pournaderi, P.

    2012-10-01

    A drop suspended in another fluid shows different dynamic behaviors in an electric field that depends on its physical properties. The phenomenon of drop deformation under the application of an electric field, in the absence of a net volume charge, is simply caused by the surface stresses. Therefore, an accurate method is required for numerical modeling of the electric driving force at the interface to handle all of the discontinuities involved in the model. For this purpose, in this study the level set method is used along with the ghost fluid method to investigate the responses of three types of drop in the presence of an electric field. Moreover, to demonstrate the accuracy of the method, the breakup modes of each electric model are carefully simulated. Finally, the results of the simulations are compared with similar numerical and experimental results from the literature. The simulation results indicate the accuracy of the method for modeling of the phenomenon over a wide range of electric capillary numbers, and particularly for the capture of the drop profile at the instant of disintegration.

  14. Note: A top-view optical approach for observing the coalescence of liquid drops

    NASA Astrophysics Data System (ADS)

    Wang, Luhai; Zhang, Guifu; Wu, Haiyi; Yang, Jiming; Zhu, Yujian

    2016-02-01

    We developed a new device that is capable of top-view optical examination of the coalescence of liquid drops. The device exhibits great potential for visualization, particularly for the early stage of liquid bridge expansion, owing to the use of a high-speed shadowgraph technique. The fluid densities of the two approaching drops and that of the ambient fluid are carefully selected to be negligibly different, which allows the size of the generated drops to be unlimitedly large in principle. The unique system design allows the point of coalescence between two drops to serve as an undisturbed optical pathway through which to image the coalescence process. The proposed technique extended the dimensionless initial finite radius of the liquid bridge to 0.001, in contrast to 0.01 obtained for conventional optical measurements. An examination of the growth of the bridge radius for a water and oil-tetrachloroethylene system provided results similar to Paulsen's power laws of the inertially limited viscous and inertial regimes. Furthermore, a miniscule shift in the center of the liquid bridge was detected at the point of crossover between the two regimes, which can be scarcely distinguished with conventional side-view techniques.

  15. Effect of ice contamination of liquid-nitrogen drops in film boiling

    NASA Technical Reports Server (NTRS)

    Schoessow, G. J.; Chmielewski, C. E.; Baumeister, K. J.

    1977-01-01

    Previously reported vaporization time data of liquid nitrogen drops in film boiling on a flat plate are about 30 percent shorter than predicted from standard laminar film boiling theory. This theory, however, had been found to successfully correlate the data for conventional fluids such as water, ethanol, benzene, or carbon tetrachloride. Experimental evidence that some of the discrepancy for cryogenic fluids results from ice contamination due to condensation is presented. The data indicate a fairly linear decrease in droplet evaporation time with the diameter of the ice crystal residue. After correcting the raw data for ice contamination along with convection, a comparison of theory with experiment shows good agreement.

  16. Effect of ice contamination on liquid-nitrogen drops in film boiling

    NASA Technical Reports Server (NTRS)

    Schoessow, G. J.; Chmielewski, C. E.; Baumeister, K. J.

    1977-01-01

    Previously reported vaporization time data of liquid nitrogen drops in film boiling on a flat plate are about 30 percent shorter than predicted from standard laminar film boiling theory. This theory, however, had been found to successfully correlate the data for conventional fluids such as water, ethanol, benzene, or carbon tetrachloride. This paper presents experimental evidence that some of the discrepancy for cryogenic fluids results from ice contamination due to condensation. The data indicate a fairly linear decrease in droplet evaporation time with the diameter of the ice crystal residue. After correcting the raw data for ice contamination along with convection, a comparison of theory with experiment shows good agreement.

  17. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, M. B.; Hargens, A. R.; Dulchavsky, S. A.; Arbeille, P.; Danielson, R. W.; Ebert, D. J.; Garcia, K. M.; Johnston, S. L.; Laurie, S. S.; Lee, S. M. C.; Liu, J.; Macias, B.; Martin, D. S.; Minkoff, L.; Ploutz-Snyder, R.; Ribeiro, L. C.; Sargsyan, A.; Smith, S. M.

    2017-01-01

    Introduction. NASA's Human Research Program is focused on addressing health risks associated with long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but now more than 50 percent of ISS astronauts have experienced more profound, chronic changes with objective structural findings such as optic disc edema, globe flattening and choroidal folds. These structural and functional changes are referred to as the visual impairment and intracranial pressure (VIIP) syndrome. Development of VIIP symptoms may be related to elevated intracranial pressure (ICP) secondary to spaceflight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration spaceflight and to determine if a relation exists with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as any VIIP-related effects of those shifts, are predicted by the crewmember's pre-flight status and responses to acute hemodynamic manipulations, specifically posture changes and lower body negative pressure. Methods. We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, and calcaneus tissue thickness (by ultrasound); (3) vascular dimensions by ultrasound (jugular veins, cerebral and carotid arteries, vertebral arteries and veins, portal vein); (4) vascular dynamics by MRI (head/neck blood flow, cerebrospinal fluid

  18. 14 CFR 23.727 - Reserve energy absorption drop test.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Reserve energy absorption drop test. 23.727... Construction Landing Gear § 23.727 Reserve energy absorption drop test. (a) If compliance with the reserve energy absorption requirement in § 23.723(b) is shown by free drop tests, the drop height may not be...

  19. 14 CFR 23.727 - Reserve energy absorption drop test.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Reserve energy absorption drop test. 23.727... Construction Landing Gear § 23.727 Reserve energy absorption drop test. (a) If compliance with the reserve energy absorption requirement in § 23.723(b) is shown by free drop tests, the drop height may not be...

  20. 14 CFR 23.727 - Reserve energy absorption drop test.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Reserve energy absorption drop test. 23.727... Construction Landing Gear § 23.727 Reserve energy absorption drop test. (a) If compliance with the reserve energy absorption requirement in § 23.723(b) is shown by free drop tests, the drop height may not be...

  1. 14 CFR 23.727 - Reserve energy absorption drop test.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Reserve energy absorption drop test. 23.727... Construction Landing Gear § 23.727 Reserve energy absorption drop test. (a) If compliance with the reserve energy absorption requirement in § 23.723(b) is shown by free drop tests, the drop height may not be...

  2. 14 CFR 23.727 - Reserve energy absorption drop test.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Reserve energy absorption drop test. 23.727... Construction Landing Gear § 23.727 Reserve energy absorption drop test. (a) If compliance with the reserve energy absorption requirement in § 23.723(b) is shown by free drop tests, the drop height may not be...

  3. Best Measuring Time for a Millikan Oil Drop Experiment

    ERIC Educational Resources Information Center

    Kapusta, J. I.

    1975-01-01

    In a Millikan oil drop experiment, there is a best measuring time for observing the drop, due to Brownian motion of the drop and the experimenter's reaction time. Derives an equation for the relative error in the measurement of the drop's excess charge, and obtains a formula for the best measuring time. (Author/MLH)

  4. Fluid flow electrophoresis in space

    NASA Technical Reports Server (NTRS)

    Griffin, R. N.

    1975-01-01

    Four areas relating to free-flow electrophoresis in space were investigated. The first was the degree of improvement over earthbound operations that might be expected. The second area of investigation covered the problems in developing a flowing buffer electrophoresis apparatus. The third area of investigation was the problem of testing on the ground equipment designed for use in space. The fourth area of investigation was the improvement to be expected in space for purification of biologicals. The results of some ground-based experiments are described. Other studies included cooling requirements in space, fluid sealing techniques, and measurement of voltage drop across membranes.

  5. Predicting Students Drop Out: A Case Study

    ERIC Educational Resources Information Center

    Dekker, Gerben W.; Pechenizkiy, Mykola; Vleeshouwers, Jan M.

    2009-01-01

    The monitoring and support of university freshmen is considered very important at many educational institutions. In this paper we describe the results of the educational data mining case study aimed at predicting the Electrical Engineering (EE) students drop out after the first semester of their studies or even before they enter the study program…

  6. Dropping In a Microgravity Environment (DIME) contest

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The first NASA Dropping In a Microgravity Environment (DIME) student competition pilot project came to a conclusion at the Glenn Research Center in April 2001. The competition involved high-school student teams who developed the concept for a microgravity experiment and prepared an experiment proposal. The two student teams - COSI Academy, sponsored by the Columbus Center of Science and Industry, and another team from Cincinnati, Ohio's Sycamore High School, designed a microgravity experiment, fabricated the experimental apparatus, and visited NASA Glenn to operate their experiment in the 2.2 Second Drop Tower. NASA and contractor personnel who conducted the DIME activity with the students. Shown (L-R) are: Eric Baumann (NASA, 2.2-second Drop Tower Facility manager), Daniel Dietrich (NASA) mentor for Sycamore High School team), Carol Hodanbosi (National Center for Microgravity Research; DIME staff), Richard DeLombard (NASA; DIME staff), Jose Carrion (GRC Akima, drop tower technician), Dennis Stocker (NASA; DIME staff), Peter Sunderland (NCMR, mentor for COSI Academy student team), Sandi Thompson (NSMR sabbatical teacher; DIME staff), Dan Woodard (MASA Microgravity Outreach Program Manager), Adam Malcolm (NASA co-op student; DIME staff), Carla Rosenberg (NCMR; DIME staff), and Twila Schneider (Infinity Technology; NASA Microgravity Research program contractor). This image is from a digital still camera; higher resolution is not available.

  7. Acoustic forcing of a liquid drop

    NASA Technical Reports Server (NTRS)

    Lyell, M. J.

    1992-01-01

    The development of systems such as acoustic levitation chambers will allow for the positioning and manipulation of material samples (drops) in a microgravity environment. This provides the capability for fundamental studies in droplet dynamics as well as containerless processing work. Such systems use acoustic radiation pressure forces to position or to further manipulate (e.g., oscillate) the sample. The primary objective was to determine the effect of a viscous acoustic field/tangential radiation pressure forcing on drop oscillations. To this end, the viscous acoustic field is determined. Modified (forced) hydrodynamic field equations which result from a consistent perturbation expansion scheme are solved. This is done in the separate cases of an unmodulated and a modulated acoustic field. The effect of the tangential radiation stress on the hydrodynamic field (drop oscillations) is found to manifest as a correction to the velocity field in a sublayer region near the drop/host interface. Moreover, the forcing due to the radiation pressure vector at the interface is modified by inclusion of tangential stresses.

  8. Primary amyloidosis presenting as "dropped head syndrome".

    PubMed

    Chuquilin, Miguel; Al-Lozi, Muhammad

    2011-06-01

    A 77-year-old man, with a history of lymphoma, presented with isolated neck extensor weakness and a 2-year history of bilateral carpal tunnel syndrome (CTS). Needle electromyography showed myopathic changes, and biopsy of cervical paraspinal muscles showed amyloid deposition in blood vessels. Amyloidosis should be considered in the differential diagnosis of dropped head syndrome.

  9. Utah Drop-Out Drug Use Questionnaire.

    ERIC Educational Resources Information Center

    Governor's Citizen Advisory Committee on Drugs, Salt Lake City, UT.

    This questionnaire assesses drug use practices in high school drop-outs. The 79 items (multiple choice or apply/not apply) are concerned with demographic data and use, use history, reasons for use/nonuse, attitudes toward drugs, availability of drugs, and drug information with respect to narcotics, amphetamines, LSD, Marijuana, and barbiturates.…

  10. Viscosity Measurement Using Drop Coalescence in Microgravity

    NASA Technical Reports Server (NTRS)

    Antar, Basil N.; Ethridge, Edwin C.; Maxwell, Daniel; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    We present in here validation studies of a new method for application in microgravity environment which measures the viscosity of highly viscous undercooled liquids using drop coalescence. The method has the advantage of avoiding heterogeneous nucleation at container walls caused by crystallization of undercooled liquids during processing. Homogeneous nucleation can also be avoided due to the rapidity of the measurement using this method. The technique relies on measurements from experiments conducted in near zero gravity environment as well as highly accurate analytical formulation for the coalescence process. The viscosity of the liquid is determined by allowing the computed free surface shape relaxation time to be adjusted in response to the measured free surface velocity for two coalescing drops. Results are presented from two sets of validation experiments for the method which were conducted on board aircraft flying parabolic trajectories. In these tests the viscosity of a highly viscous liquid, namely glycerin, was determined at different temperatures using the drop coalescence method described in here. The experiments measured the free surface velocity of two glycerin drops coalescing under the action of surface tension alone in low gravity environment using high speed photography. The liquid viscosity was determined by adjusting the computed free surface velocity values to the measured experimental data. The results of these experiments were found to agree reasonably well with the known viscosity for the test liquid used.

  11. Lightweight, Economical Device Alleviates Drop Foot

    NASA Technical Reports Server (NTRS)

    Deis, B. C.

    1983-01-01

    Corrective apparatus alleviates difficulties in walking for victims of drop foot. Elastic line attached to legband provides flexible support to toe of shoe. Device used with flat (heelless) shoes, sneakers, crepe-soled shoes, canvas shoes, and many other types of shoes not usable with short leg brace.

  12. Sessile drop deformations under an impinging jet

    NASA Astrophysics Data System (ADS)

    Feng, James Q.

    2015-08-01

    The problem of steady axisymmetric deformations of a liquid sessile drop on a flat solid surface under an impinging gas jet is of interest for understanding the fundamental behavior of free surface flows as well as for establishing the theoretical basis in process design for the Aerosol direct-write technology. It is studied here numerically using a Galerkin finite-element method, by computing solutions of Navier-Stokes equations. For effective material deposition in Aerosol printing, the desired value of Reynolds number for the laminar gas jet is found to be greater than ~500. The sessile drop can be severely deformed by an impinging gas jet when the capillary number is approaching a critical value beyond which no steady axisymmetric free surface deformation can exist. Solution branches in a parameter space show turning points at the critical values of capillary number, which typically indicate the onset of free surface shape instability. By tracking solution branches around turning points with an arc-length continuation algorithm, critical values of capillary number can be accurately determined. Near turning points, all the free surface profiles in various parameter settings take a common shape with a dimple at the center and bulge near the contact line. An empirical formula for the critical capillary number for sessile drops with contact angle is derived for typical ranges of jet Reynolds number and relative drop sizes especially pertinent to Aerosol printing.

  13. Orion Parachute Drop Test, July 18

    NASA Video Gallery

    A C-17 plane dropped a test version of Orion from an altitude of 25,000 feet above the U.S. Army Yuma Proving Ground in southwestern Arizona on July 18, 2012. This test was the second to use an Ori...

  14. How to Handle Drop-in Visitors.

    ERIC Educational Resources Information Center

    Partin, Ronald L.

    1988-01-01

    Although interruptions are an unavoidable part of the principal's job, a completely open-door policy for drop-in visitors could divert attention from planning and other priorities. This article suggests ways for principals to minimize the number of visitors and the length of visits, including keeping people standing, providing uncomfortable…

  15. Inverted drop testing and neck injury potential.

    PubMed

    Forrest, Stephen; Herbst, Brian; Meyer, Steve; Sances, Anthony; Kumaresan, Srirangam

    2003-01-01

    Inverted drop testing of vehicles is a methodology that has long been used by the automotive industry and researchers to test roof integrity and is currently being considered by the National Highway Traffic Safety Administration as a roof strength test. In 1990 a study was reported which involved 8 dolly rollover tests and 5 inverted drop tests. These studies were conducted with restrained Hybrid III instrumented Anthropometric Test Devices (ATD) in production and rollcaged vehicles to investigate the relationship between roof strength and occupant injury potential. The 5 inverted drop tests included in the study provided a methodology producing "repeatable roof impacts" exposing the ATDs to the similar impact environment as those seen in the dolly rollover tests. Authors have conducted two inverted drop test sets as part of an investigation of two real world rollover accidents. Hybrid-III ATD's were used in each test with instrumented head and necks. Both test sets confirm that reduction of roof intrusion and increased headroom can significantly enhance occupant protection. In both test pairs, the neck force of the dummy in the vehicle with less crush and more survival space was significantly lower. Reduced roof crush and dynamic preservation of the occupant survival space resulted in only minor occupant contact and minimal occupant loading, establishing a clear causal relationship between roof crush and neck injuries.

  16. 49 CFR 178.965 - Drop test.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... tests are to be performed with the solid or liquid to be transported or with a non-hazardous material... Large Packaging design types and performed periodically as specified in § 178.955(e) of this subpart. (b... § 178.960(d). (d) Test method. (1) Samples of all Large Packaging design types must be dropped onto...

  17. 49 CFR 178.965 - Drop test.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... tests are to be performed with the solid or liquid to be transported or with a non-hazardous material... Large Packaging design types and performed periodically as specified in § 178.955(e) of this subpart. (b... § 178.960(d). (d) Test method. (1) Samples of all Large Packaging design types must be dropped onto...

  18. Behavior Of Evaporating Liquid Drops In Clusters

    NASA Technical Reports Server (NTRS)

    Bellan, Josette

    1990-01-01

    Report presents critical analysis of methods, developed for calculating behavior of evaporating liquid drops in dense and dilute clusters. Essential to understanding variety of physical and chemical phenomena occurring in combustion of sprayed fuels and in sprays used in agriculture, food industry, and painting. Presents insights on important aspects of two-phase flow.

  19. 49 CFR 178.965 - Drop test.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    .... Water/anti-freeze solutions with a minimum specific gravity of 0.95 for testing at −18 °C (0 °F) or... having essentially the same physical characteristics. (3) The specific gravity and viscosity of a...: (i) Where the substances to be carried have a specific gravity not exceeding 1.2, the drop...

  20. 49 CFR 178.965 - Drop test.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    .... Water/anti-freeze solutions with a minimum specific gravity of 0.95 for testing at −18 °C (0 °F) or... having essentially the same physical characteristics. (3) The specific gravity and viscosity of a...: (i) Where the substances to be carried have a specific gravity not exceeding 1.2, the drop...

  1. 49 CFR 178.810 - Drop test.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... solutions with a minimum specific gravity of 0.95 for testing at −18 °C (0 °F) or lower are considered... material having essentially the same physical characteristics. (3) The specific gravity and viscosity of a...: (i) Where the substances to be carried have a specific gravity not exceeding 1.2, the drop...

  2. 49 CFR 178.810 - Drop test.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... solutions with a minimum specific gravity of 0.95 for testing at −18 °C (0 °F) or lower are considered... material having essentially the same physical characteristics. (3) The specific gravity and viscosity of a...: (i) Where the substances to be carried have a specific gravity not exceeding 1.2, the drop...

  3. 49 CFR 178.603 - Drop test.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... of anti-freeze. Water/anti-freeze solutions with a minimum specific gravity of 0.95 for testing at... is performed with water: (i) Where the materials to be carried have a specific gravity not exceeding...) Where the materials to be transported have a specific gravity exceeding 1.2, the drop height must...

  4. 49 CFR 178.603 - Drop test.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... specific gravity of 0.95 for testing at −18 °C (0 °F) or lower are considered acceptable test liquids. Test... specific gravity not exceeding 1.2, drop height must be determined according to packing group, as follows...: 0.8 m (2.6 feet). (ii) Where the materials to be transported have a specific gravity exceeding...

  5. 49 CFR 178.603 - Drop test.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... of anti-freeze. Water/anti-freeze solutions with a minimum specific gravity of 0.95 for testing at... is performed with water: (i) Where the materials to be carried have a specific gravity not exceeding...) Where the materials to be transported have a specific gravity exceeding 1.2, the drop height must...

  6. 49 CFR 178.810 - Drop test.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... solutions with a minimum specific gravity of 0.95 for testing at −18 °C (0 °F) or lower are considered... material having essentially the same physical characteristics. (3) The specific gravity and viscosity of a...: (i) Where the substances to be carried have a specific gravity not exceeding 1.2, the drop...

  7. Electrohydrodynamic manipulation of particles adsorbed on the surface of a drop.

    PubMed

    Amah, Edison; Shah, Kinnari; Fischer, Ian; Singh, Pushpendra

    2016-02-14

    In our previous studies we have shown that particles adsorbed on the surface of a drop can be concentrated at its poles or equator by applying a uniform electric field. This happens because even when the applied electric field is uniform the electric field on the surface of the drop is nonuniform, and so particles adsorbed on the surface are subjected to dielectrophoretic (DEP) forces. In this paper, we study the behavior of adsorbed particles at low electric field frequencies when the drop and ambient liquids are weakly conducting dielectric liquids, and model it using a leaky dielectric model. The electrohydrodynamic (EHD) flow which arises because of the accumulation of charge on the surface of the drop can be from pole-to-equator or equator-to-pole depending on the properties of the drop and ambient liquids. The flow however diminishes with increasing frequency and there is a critical frequency at which the drag force on a particle due to the EHD flow becomes equal to the DEP force, and above this critical frequency the DEP force dominates. When the fluid and particles properties are such that the EHD and DEP forces are in the opposite directions, particles can be collected at the poles or the equator, and also can be moved from the poles to the equator, or vice versa, by varying the frequency. Also, it is possible to separate the particles of a binary mixture when the critical frequencies of the two types of particles are different.

  8. Pressure drop characteristics of cryogenic mixed refrigerant at macro and micro channel heat exchangers

    NASA Astrophysics Data System (ADS)

    Baek, Seungwhan; Jeong, Sangkwon; Hwang, Gyuwan

    2012-12-01

    Mixed Refrigerant-Joule Thomson (MR-JT) refrigerators are widely used in various kinds of cryogenic systems these days. The temperature glide effect is one of the major features of using mixed refrigerants since a recuperative heat exchanger in a MR-JT refrigerator is utilized for mostly two-phase flow. Although a pressure drop estimation for a multi-phase and multi-component fluid in the cryogenic temperature range is necessarily required in MR-JT refrigerator heat exchanger designs, it has been rarely discussed so far. In this paper, macro heat exchangers and micro heat exchangers are compared in order to investigate the pressure drop characteristics in the experimental MR-JT refrigerator operation. The tube in tube heat exchanger (TTHE) is a well-known macro-channel heat exchanger in MR-JT refrigeration. Printed Circuit Heat Exchangers (PCHEs) have been developed as a compact heat exchanger with micro size channels. Several two-phase pressure drop correlations are examined to discuss the experimental pressure measurement results. The result of this paper shows that cryogenic mixed refrigerant pressure drop can be estimated with conventional two-phase pressure drop correlations if an appropriate flow pattern is identified.

  9. Investigation of Contact Angle Behavior and Stability of Drops to Airflow Forcing on Rough Surfaces

    NASA Astrophysics Data System (ADS)

    Schmucker, Jason; White, Edward

    2011-11-01

    A method for measuring full-field, instantaneous drop interface profiles on rough surfaces has been implemented to study contact angles and stability to wind forcing on metallic surfaces with micron-scale roughness. Wind tunnel experiments are conducted to produce criteria for runback of drops and set these thresholds for measured water drops spanning a range of Bond numbers from Bo = 0 . 5 to 5 on roughness in the range of RA = 0 . 8 to 4 . 9 with drop based Reynolds numbers spanning an order of magnitude. More importantly, these stability limits are tested with particular care taken to observe their relation to the behavior of both the contact line and contact angle distribution as the drop adjusts its configuration to find a stable condition until it is no longer able to do so and is blown downstream. Results such as critical shear rates and contact angles are discussed and compared with previous numerical studies in the literature such as Dimitrakopoulos [J.Fluid.Mech. 580, 2007] and Ding and Spelt [J.Coll.Sci. 599, 2008] along with experimental results such as Milne [Langmuir 25:24, 2009].

  10. Monte Carlo Method for Predicting a Physically Based Drop Size Distribution Evolution of a Spray

    NASA Astrophysics Data System (ADS)

    Tembely, Moussa; Lécot, Christian; Soucemarianadin, Arthur

    2010-03-01

    We report in this paper a method for predicting the evolution of a physically based drop size distribution of a spray, by coupling the Maximum Entropy Formalism and the Monte Carlo scheme. Using the discrete or continuous population balance equation, a Mass Flow Algorithm is formulated taking into account interactions between droplets via coalescence. After deriving a kernel for coalescence, we solve the time dependent drop size distribution equation using a Monte Carlo method. We apply the method to the spray of a new print-head known as a Spray On Demand (SOD) device; the process exploits ultrasonic spray generation via a Faraday instability where the fluid/structure interaction causing the instability is described by a modified Hamilton's principle. This has led to a physically-based approach for predicting the initial drop size distribution within the framework of the Maximum Entropy Formalism (MEF): a three-parameter generalized Gamma distribution is chosen by using conservation of mass and energy. The calculation of the drop size distribution evolution by Monte Carlo method shows the effect of spray droplets coalescence both on the number-based or volume-based drop size distributions.

  11. Fast and accurate pressure-drop prediction in straightened atherosclerotic coronary arteries.

    PubMed

    Schrauwen, Jelle T C; Koeze, Dion J; Wentzel, Jolanda J; van de Vosse, Frans N; van der Steen, Anton F W; Gijsen, Frank J H

    2015-01-01

    Atherosclerotic disease progression in coronary arteries is influenced by wall shear stress. To compute patient-specific wall shear stress, computational fluid dynamics (CFD) is required. In this study we propose a method for computing the pressure-drop in regions proximal and distal to a plaque, which can serve as a boundary condition in CFD. As a first step towards exploring the proposed method we investigated ten straightened coronary arteries. First, the flow fields were calculated with CFD and velocity profiles were fitted on the results. Second, the Navier-Stokes equation was simplified and solved with the found velocity profiles to obtain a pressure-drop estimate (Δp (1)). Next, Δp (1) was compared to the pressure-drop from CFD (Δp CFD) as a validation step. Finally, the velocity profiles, and thus the pressure-drop were predicted based on geometry and flow, resulting in Δp geom. We found that Δp (1) adequately estimated Δp CFD with velocity profiles that have one free parameter β. This β was successfully related to geometry and flow, resulting in an excellent agreement between Δp CFD and Δp geom: 3.9 ± 4.9% difference at Re = 150. We showed that this method can quickly and accurately predict pressure-drop on the basis of geometry and flow in straightened coronary arteries that are mildly diseased.

  12. Axisymmetric shapes and stability of charged drops in an external electric field

    NASA Astrophysics Data System (ADS)

    Basaran, O. A.; Scriven, L. E.

    1989-05-01

    A highly conducting charged drop that is surrounded by a fluid insulator of another density can be levitated by suitably applying a uniform electric field. Axisymmetric equilibrium shapes and stability of the levitated drop are found by solving simultaneously the augmented Young-Laplace equation for surface shape and the Laplace equation for the elecric field, together with constraints of fixed drop volume, charge, and center of mass. The means are a method of subdomains, finite element basis functions, and Galerkin's method of weighted residuals, all facilitated by a large-scale computer. Shape families of fixed charge are treated systematically by first-order continuation. Previous analyses by Abbas et al. in 1967 and Abbas and Latham in 1969, in which the shapes of levitated drops are approximated as spheroids, are corrected. The new analysis shows that drops charged to less than the Rayleigh limit lose shape stability at turning points, with respect to external field strength, and that the instability seen in experiments of Doyle et al. in 1964 and others is not a bifurcation to a family of two-lobed shapes, but rather is a related imperfect bifurcation.

  13. Axisymmetric shapes and stability of charged drops in an external electric field

    NASA Astrophysics Data System (ADS)

    Basaran, O. A.; Scriven, L. E.

    1989-05-01

    A highly conducting charged drop that is surrounded by a fluid insulator of another density can be levitated by suitably applying a uniform electric field. Axisymmetric equilibrium shapes and stability of the levitated drop are found by solving simultaneously the augmented Young-Laplace equation for surface shape and the Laplace equation for the electric field, together with constraints of fixed drop volume, charge, and center of mass. The means are a method of subdomains, finite element basis functions, and Galerkin's method of weighted residuals, all facilitated by a large-scale computer. Shape families of fixed charge are treated systematically by first-order continuation. Previous analyses by Abbas et al. in 1967 and Abbas and Latham in 1969, in which the shapes of levitated drops are approximated as spheroids, are corrected. The new analysis shows that drops charged to less than the Rayleigh limit lose shape stability at turning points, with respect to external field strength, and that the instability seen in experiments of Doyle et al. in 1964 and others is not a bifurcation to a family of two-lobed shapes, but rather is a related imperfect bifurcation.

  14. Equilibrium electro-deformation of a surfactant-laden viscous drop

    NASA Astrophysics Data System (ADS)

    Nganguia, Herve; Young, Y.-N.; Vlahovska, Petia M.; Bławzdziewcz, Jerzy; Zhang, J.; Lin, H.

    2013-09-01

    We theoretically investigate the deformation of a viscous drop covered with non-diffusing insoluble surfactant under a uniform DC electric field. At equilibrium, surfactant immobilizes the spheroidal drop surface and completely suppresses the fluid flow. In this work we focus on the equilibrium electro-deformation of a surfactant-laden drop in the leaky dielectric framework by developing (1) a second-order small-deformation analysis and (2) a spheroidal model for a highly deformed (prolate or oblate) drop. Both models are compared against experimental data and numerical simulation results in the literature. Our analysis shows how the existence of equilibrium spheroidal drop depends on the permittivity ratio, conductivity ratio, surfactant coverage, and the elasticity number. Furthermore, the spheroidal model highlights that differences between surfactant effects, such as tip stretching and surface dilution effects, are greatly amplified at large surfactant coverage and high electric capillary number. These surfactant effects are well captured in the spheroidal model, but cannot be described in the second-order small-deformation theory.

  15. Rapid analysis of neonicotinoid insecticides in guttation drops of corn seedlings obtained from coated seeds.

    PubMed

    Tapparo, Andrea; Giorio, Chiara; Marzaro, Matteo; Marton, Daniele; Soldà, Lidia; Girolami, Vincenzo

    2011-06-01

    Regarding the hypothesis that neonicotinoid insecticides used for seed coating of agricultural crops - mainly corn, sunflower and seed rape - are related to the extensive death of honey bees, the phenomenon of corn seedling guttation has been recently considered as a possible route of exposure of bees to these systemic insecticides. In the present study, guttation drops of corn plants obtained from commercial seeds coated with thiamethoxam, clothianidin, imidacloprid and fipronil have been analyzed by an optimized fast UHPLC-DAD procedure showing excellent detection limits and accuracy, both adequate for the purpose. The young plants grown both in pots - in greenhouse - and in open field from coated seeds, produced guttation solutions containing high levels of the neonicotinoid insecticides (up to 346 mg L(-1) for imidacloprid, 102 mg L(-1) for clothianidin and 146 mg L(-1) for thiamethoxam). These concentration levels may represent lethal doses for bees that use guttation drops as a source of water. The neonicotinoid concentrations in guttation drops progressively decrease during the first 10-15 days after the emergence of the plant from the soil. Otherwise fipronil, which is a non-systemic phenylpyrazole insecticide, was never detected into guttation drops. Current results confirm that the physiological fluids of the corn plant can effectively transfer neonicotinoid insecticides from the seed onto the surface of the leaves, where guttation drops may expose bees and other insects to elevated doses of neurotoxic insecticides.

  16. Drops: The collapse of capillary jets

    PubMed Central

    Cordoba, Antonio; Cordoba, Diego; Fefferman, Charles; Fontelos, Marco A.

    2002-01-01

    The appearance of fluid filaments during the evolution of a viscous fluid jet is a commonly observed phenomenon. It is shown here that the break-up of such a jet subject to capillary forces is impossible through the collapse of a uniform filament. PMID:12172005

  17. Drop floating on a granular raft

    NASA Astrophysics Data System (ADS)

    Jambon-Puillet, Etienne; Protière, Suzie

    2016-09-01

    This paper is associated with a poster winner of a 2015 APS/DFD Milton van Dyke Award for work presented at the DFD Gallery of Fluid Motion. The original poster is available from the Gallery of Fluid Motion, http://dx.doi.org/10.1103/APS.DFD.2015.GFM.P0008

  18. Instabilities of volatile films and drops

    NASA Astrophysics Data System (ADS)

    Murisic, Nebojsa

    2008-12-01

    We report on instabilities during spreading of volatile liquids, with emphasis on the novel instability observed when isopropyl alcohol (IPA) is deposited on a monocrystalline silicon (Si) wafer. This instability is characterized by emission of drops ahead of the expanding front, with each drop followed by smaller, satellite droplets, forming the structures which we nickname "octopi" due to their appearance. A less volatile liquid, or a substrate of larger heat conductivity, suppress this instability. In addition, we examine the spreading of drops of water (DIW)-IPA mixtures on both Si wafers and plain glass slides, and describe the variety of contact line instabilities which appear. We find that the decrease of IPA concentration in mixtures leads to transition from "octopi" to mushroom-like instabilities. Through manipulation of our experimental set up, we also find that the mechanism responsible for these instabilities appears to be mostly insensitive to both the external application of convection to the gas phase, and the doping of the gas phase with vapor in order to create the saturated environment. In order to better understand the "octopi" instability, we develop a theoretical model for evaporation of a pure liquid drop on a thermally conductive solid substrate. This model includes all relevant physical effects, including evaporation, thermal conductivity in both liquid and solid, (thermocapillary) Marangoni effect, vapor recoil, disjoining pressure, and gravity. The crucial ingredient in this problem is the evaporation model, since it influences both the motion of the drop contact line, and the temperature profiles along the liquid-solid and liquid-gas interfaces. We consider two evaporation models: the equilibrium "lens" model and the non-equilibrium one-sided (NEOS) model. Along with the assumption of equilibrium at the liquid-gas interface, the "lens" model also assumes that evaporation proceeds in a (vapor) diffusion-limited regime, therefore bringing

  19. Simulations of Evaporating Multicomponent Fuel Drops

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Le Clercq, Patrick

    2005-01-01

    A paper presents additional information on the subject matter of Model of Mixing Layer With Multicomponent Evaporating Drops (NPO-30505), NASA Tech Briefs, Vol. 28, No. 3 (March 2004), page 55. To recapitulate: A mathematical model of a three-dimensional mixing layer laden with evaporating fuel drops composed of many chemical species has been derived. The model is used to perform direct numerical simulations in continuing studies directed toward understanding the behaviors of sprays of liquid petroleum fuels in furnaces, industrial combustors, and engines. The model includes governing equations formulated in an Eulerian and a Lagrangian reference frame for the gas and drops, respectively, and incorporates a concept of continuous thermodynamics, according to which the chemical composition of a fuel is described by use of a distribution function. In this investigation, the distribution function depends solely on the species molar weight. The present paper reiterates the description of the model and discusses further in-depth analysis of the previous results as well as results of additional numerical simulations assessing the effect of the mass loading. The paper reiterates the conclusions reported in the cited previous article, and states some new conclusions. Some new conclusions are: 1. The slower evaporation and the evaporation/ condensation process for multicomponent-fuel drops resulted in a reduced drop-size polydispersity compared to their single-component counterpart. 2. The inhomogeneity in the spatial distribution of the species in the layer increases with the initial mass loading. 3. As evaporation becomes faster, the assumed invariant form of the molecular- weight distribution during evaporation becomes inaccurate.

  20. Annual Occurrence of Meteorite-Dropping Fireballs

    NASA Astrophysics Data System (ADS)

    Konovalova, Natalia; Jopek, Tadeusz J.

    2016-07-01

    The event of Chelyabinsk meteorite has brought about change the earlier opinion about limits of the sizes of potentially dangerous asteroidal fragments that crossed the Earth's orbit and irrupted in the Earth's atmosphere making the brightest fireball. The observations of the fireballs by fireball networks allows to get the more precise data on atmospheric trajectories and coordinates of predicted landing place of the meteorite. For the reason to search the periods of fireball activity is built the annual distribution of the numbers of meteorites with the known fall dates and of the meteorite-dropping fireballs versus the solar longitude. The resulting profile of the annual activity of meteorites and meteorite-dropping fireballs shows several periods of increased activity in the course of the year. The analysis of the atmospheric trajectories and physical properties of sporadic meteorite-dropping fireballs observed in Tajikistan by instrumental methods in the summer‒autumn periods of increased fireballs activity has been made. As a result the structural strength, the bulk density and terminal mass of the studied fireballs that can survive in the Earth atmosphere and became meteorites was obtained. From the photographic IAU MDC_2003 meteor database and published sources based on the orbit proximity as determined by D-criterion of Southworth and Hawkins the fireballs that could be the members of group of meteorite-dropping fireballs, was found. Among the near Earth's objects (NEOs) the searching for parent bodies for meteorite-dropping fireballs was made and the evolution of orbits of these objects in the past on a long interval of time was investigated.

  1. Lifetime of oil drops pressed by buoyancy against a planar interface: Large drops

    NASA Astrophysics Data System (ADS)

    Rojas, Clara; García-Sucre, Máximo; Urbina-Villalba, Germán

    2010-11-01

    In a previous report [C. Rojas, G. Urbina-Villalba, and M. García-Sucre, Phys. Rev. E 81, 016302 (2010)10.1103/PhysRevE.81.016302] it was shown that emulsion stability simulations are able to reproduce the lifetime of micrometer-size drops of hexadecane pressed by buoyancy against a planar water-hexadecane interface. It was confirmed that small drops (ri<10μm) stabilized with β -casein behave as nondeformable particles, moving with a combination of Stokes and Taylor tensors as they approach the interface. Here, a similar methodology is used to parametrize the potential of interaction of drops of soybean oil stabilized with bovine serum albumin. The potential obtained is then employed to study the lifetime of deformable drops in the range 10≤ri≤1000μm . It is established that the average lifetime of these drops can be adequately replicated using the model of truncated spheres. However, the results depend sensibly on the expressions of the initial distance of deformation and the maximum film radius used in the calculations. The set of equations adequate for large drops is not satisfactory for medium-size drops (10≤ri≤100μm) , and vice versa. In the case of large particles, the increase in the interfacial area as a consequence of the deformation of the drops generates a very large repulsive barrier which opposes coalescence. Nevertheless, the buoyancy force prevails. As a consequence, it is the hydrodynamic tensor of the drops which determine the characteristic behavior of the lifetime as a function of the particle size. While the average values of the coalescence time of the drops can be justified by the mechanism of film thinning, the scattering of the experimental data of large drops cannot be rationalized using the methodology previously described. A possible explanation of this phenomenon required elaborate simulations which combine deformable drops, capillary waves, repulsive interaction forces, and a time-dependent surfactant adsorption.

  2. The impact of mass flow and masking on the pressure drop of air filter in heavy-duty diesel engine

    NASA Astrophysics Data System (ADS)

    Hoseeinzadeh, Sepideh; Gorji-Bandpy, Mofid

    2012-04-01

    This paper presents a computational fluid dynamics (CFD) calculation approach to predict and evaluate the impact of the mass-flow inlet on the pressure drop of turbocharger`s air filtfer in heavy-duty diesel engine. The numerical computations were carried out using a commercial CFD program whereas the inlet area of the air filter consisted of several holes connected to a channel. After entering through the channel, the air passes among the holes and enters the air filter. The effect of masking holes and hydraulic diameter is studied and investigated on pressure drop. The results indicate that pressure drop increase with decreasing of hydraulic diameter and masking of the holes has considerable affect on the pressure drop.

  3. Fluid Mechanics

    NASA Astrophysics Data System (ADS)

    Pnueli, David; Gutfinger, Chaim

    1997-01-01

    This text is intended for the study of fluid mechanics at an intermediate level. The presentation starts with basic concepts, in order to form a sound conceptual structure that can support engineering applications and encourage further learning. The presentation is exact, incorporating both the mathematics involved and the physics needed to understand the various phenomena in fluid mechanics. Where a didactical choice must be made between the two, the physics prevails. Throughout the book the authors have tried to reach a balance between exact presentation, intuitive grasp of new ideas, and creative applications of concepts. This approach is reflected in the examples presented in the text and in the exercises given at the end of each chapter. Subjects treated are hydrostatics, viscous flow, similitude and order of magnitude, creeping flow, potential flow, boundary layer flow, turbulent flow, compressible flow, and non-Newtonian flows. This book is ideal for advanced undergraduate students in mechanical, chemical, aerospace, and civil engineering. Solutions manual available.

  4. Fluid extraction

    DOEpatents

    Wai, Chien M.; Laintz, Kenneth E.

    1999-01-01

    A method of extracting metalloid and metal species from a solid or liquid material by exposing the material to a supercritical fluid solvent containing a chelating agent is described. The chelating agent forms chelates that are soluble in the supercritical fluid to allow removal of the species from the material. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is a fluorinated .beta.-diketone. In especially preferred embodiments the extraction solvent is supercritical carbon dioxide, and the chelating agent comprises a fluorinated .beta.-diketone and a trialkyl phosphate, or a fluorinated .beta.-diketone and a trialkylphosphine oxide. Although a trialkyl phosphate can extract lanthanides and actinides from acidic solutions, a binary mixture comprising a fluorinated .beta.-diketone and a trialkyl phosphate or a trialkylphosphine oxide tends to enhance the extraction efficiencies for actinides and lanthanides. The method provides an environmentally benign process for removing contaminants from industrial waste without using acids or biologically harmful solvents. The method is particularly useful for extracting actinides and lanthanides from acidic solutions. The chelate and supercritical fluid can be regenerated, and the contaminant species recovered, to provide an economic, efficient process.

  5. Approach run increases preactivation and eccentric phases muscle activity during drop jumps from different drop heights.

    PubMed

    Ruan, Mianfang; Li, Li

    2010-10-01

    The purpose of this study was to investigate the effects of a horizontal approach run and drop height on the activation of lower extremity muscles during drop jumps. Ten participants performed drop jumps from drop heights of 15, 30, 45 and 60cm with zero (standing), one, two, and three approach run steps. The EMG activities of the Gluteus Maximus (GM), Rectus Femoris (RF), Biceps Femoris (BF), Vastus Lateralis (VL), Tibialis Anterior (TA), Gastrocnemius (GA) and Soleus (SO) were recorded, full-wave rectified, and averaged (aEMG) during the preactivation (50ms before touchdown), downward, and push-off phases. Increasing drop height did not enhance the muscle activation level of any examined muscles except GA. During the preactivation phase, the aEMG of all muscles except TA increased with the number of approach run steps. The aEMG of RF, BF, VL, and SO also increased with the number of approach run steps during the downward phase, while no aEMG changes were observed during the push-off phase. These results suggest that a horizontal approach run preceding the drop jump is an effective strategy for increasing the muscle preactivation level, which contributes to a higher level of muscle activity during the eccentric contraction phase and could potentially contribute to the reported higher power output during the concentric contraction phase.

  6. Liquid drops on vertical and inclined surfaces; I. An experimental study of drop geometry.

    PubMed

    ElSherbini, A I; Jacobi, A M

    2004-05-15

    Experiments have been conducted to investigate the geometric parameters necessary to describe the shapes of liquid drops on vertical and inclined plane surfaces. Two liquids and eight surfaces have been used to study contact angles, contact lines, profiles, and volumes of drops of different sizes for a range of surface conditions. The results show the contact-angle variation along the circumference of a drop to be best fit by a third-degree polynomial in the azimuthal angle. This contact-angle function is expressed in terms of the maximum and minimum contact angles of the drop, which are determined for various conditions. The maximum contact angle, thetamax, is approximately equal to the advancing contact angle, thetaA, of the liquid on the surface. As the Bond number, Bo, increases from 0 to a maximum, the minimum contact angle, thetamin, decreases almost linearly from the advancing to the receding angle. A general relation is found between thetamin/thetaA and Bo for different liquid-surface combinations. The drop contour can be described by an ellipse, with the aspect ratio increasing with Bo. These experimental results are valuable in modeling drop shape, as presented in Part II of this work.

  7. Dropping In a Microgravity Environment (DIME) contest

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The first NASA Dropping In a Microgravity Environment (DIME) student competition pilot project came to a conclusion at the Glenn Research Center in April 2001. The competition involved high-school student teams who developed the concept for a microgravity experiment and prepared an experiment proposal. The two student teams - COSI Academy, sponsored by the Columbus Center of Science and Industry, and another team from Cincinnati, Ohio's Sycamore High School, designed a microgravity experiment, fabricated the experimental apparatus, and visited NASA Glenn to operate their experiment in the 2.2 Second Drop Tower. This is the interior of the Sycamore High School (Cincinnati, Ohio) students' experiment to observe the flame spreading on a 100 percent cotton T-shirt under low-g. This image is from a digital still camera; higher resolution is not available.

  8. Control of Drop Motion by Mechanical Vibrations

    NASA Astrophysics Data System (ADS)

    Bestehorn, Michael

    2014-11-01

    Since the first experimental observations of Michael Faraday in 1831 it is known that a vibrating liquid may show an instability of its flat free surface with respect to oscillating regular surface patterns. We study thin liquid films on a horizontal substrate in the long wave approximation. The films are parametrically excited by mechanical horizontal or inclined oscillations. Inertia effects are taken into account and the standard thin film formulation is extended by a second equation for the vertically averaged mass flux. The films can be additionally unstable by Van der Waals forces on a partially wetting substrate, leading to the formation of drops. These drops can be manipulated by the vibrations to move in a desired direction. Linear results based on a damped complex valued Mathieu equation as well as fully nonlinear results using a reduced model will be presented, for more details see.

  9. Dropping In a Microgravity Environment (DIME) contest

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The first NASA Dropping In a Microgravity Environment (DIME) student competition pilot project came to a conclusion at the Glenn Research Center in April 2001. The competition involved high-school student teams who developed the concept for a microgravity experiment and prepared an experiment proposal. The two student teams - COSI Academy, sponsored by the Columbus Center of Science and Industry, and another team from Cincinnati, Ohio's Sycamore High School, designed a microgravity experiment, fabricated the experimental apparatus, and visited NASA Glenn to operate their experiment in the 2.2 Second Drop Tower. Here Carol Hodanbosi of the National Center for Microgravity Research and Jose Carrion, a lab mechanic with AKAC, prepare a student experiment package (inside the silver-colored frame) inside the orange-colored drag shield that encloses all experiment hardware. This image is from a digital still camera; higher resolution is not available.

  10. Faraday instability of a spherical drop

    NASA Astrophysics Data System (ADS)

    Ebo Adou, A.; Tuckerman, Laurette; Shin, Seungwon; Chergui, Jalel; Juric, Damir

    2014-11-01

    A liquid drop subjected to an oscillatory radial force comprises a spherical version of the Faraday instability, with a subharmonic response which is half of the forcing frequency. The time-dependent shape of the drop and the velocity field in and around it are calculated using BLUE, a code based on a hybrid Front Tracking/Level-set algorithm for Lagrangian tracking of arbitrarily deformable phase interfaces. We compare this shape with the spherical harmonic selected at onset, calculated by adapting the Floquet stability analysis of Kumar and Tuckerman to a spherical geometry. We interpret the shape in light of theoretical results by Busse, Matthews and others concerning pattern formation in the presence of O(3) symmetry.

  11. Interface solidification of impinging metal drops

    NASA Astrophysics Data System (ADS)

    de Ruiter, Jolet; Soto, Dan; Varanasi, Kripa

    2016-11-01

    Molten metal droplet deposition is important in manufacturing techniques such as spray deposition and metal inkjet printing. Key parameters are the final splat morphology and its adhesion to the base substrate. How to control these parameters is still poorly understood, since droplet deformation, cooling and solidification happen simultaneously. Here, we studied the contact patch formed between the metal drop and the base substrate, varying the thermal properties and the initial temperature of the substrate, and the initial temperature of the drop. We identify various scenarios for interface solidification, including smooth liquid-spread contact patches, entrapment of air pockets, and transient re-melting of the interface. The transitions between various scenarios can be rationalized from the interfacial temperature estimated by heat conduction, and taking into account the flow of liquid metal.

  12. DROP: Durable Reconnaissance and Observation Platform

    NASA Technical Reports Server (NTRS)

    Parness, Aaron; McKenzie, Clifford F.

    2012-01-01

    Robots have been a valuable tool for providing a remote presence in areas that are either inaccessible or too dangerous for humans. Having a robot with a high degree of adaptability becomes crucial during such events. The adaptability that comes from high mobility and high durability greatly increases the potential uses of a robot in these situations, and therefore greatly increases its usefulness to humans. DROP is a lightweight robot that addresses these challenges with the capability to survive large impacts, carry a usable payload, and traverse a variety of surfaces, including climbing vertical surfaces like wood, stone, and concrete. The platform is crash-proof, allowing it to be deployed in ways including being dropped from an unmanned aerial vehicle or thrown from a large MSL-class (Mars Science Laboratory) rover.

  13. Dropping In a Microgravity Environment (DIME) Contest

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The first NASA Dropping In a Microgravity Environment (DIME) student competition pilot project came to a conclusion at the Glenn Research Center in April 2001. The competition involved high-school student teams who developed the concept for a microgravity experiment and prepared an experiment proposal. The two student teams - COSI Academy, sponsored by the Columbus Center of Science and Industry, and another team from Cincinnati, Ohio's Sycamore High School, designed a microgravity experiment, fabricated the experimental apparatus, and visited NASA Glenn to operate their experiment in the 2.2 Second Drop Tower. Students from Sycamore High School in Cincinnati, Ohio (girls), and the COSI Academy, Columbus, Ohio (boys), participated. This image is from a digital still camera; higher resolution is not available.

  14. Diffraction and interference of walking drops

    NASA Astrophysics Data System (ADS)

    Pucci, Giuseppe; Harris, Daniel M.; Bush, John W. M.

    2016-11-01

    A decade ago, Yves Couder and Emmanuel Fort discovered a wave-particle association on the macroscopic scale: a drop can bounce indefinitely on a vibrating bath of the same liquid and can be piloted by the waves that it generates. These walking droplets have been shown to exhibit several quantum-like features, including single-particle diffraction and interference. Recently, the original diffraction and interference experiments of Couder and Fort have been revisited and contested. We have revisited this system using an improved experimental set-up, and observed a strong dependence of the behavior on system parameters, including drop size and vibrational forcing. In both the single- and the double-slit geometries, the diffraction pattern is dominated by the interaction of the walking droplet with a planar boundary. Critically, in the double-slit geometry, the walking droplet is influenced by both slits by virtue of its spatially extended wave field. NSF support via CMMI-1333242.

  15. Bag breakup of low viscosity drops in the presence of a continuous air jet

    SciTech Connect

    Kulkarni, V. Sojka, P. E.

    2014-07-15

    This work examines the breakup of a single drop of various low viscosity fluids as it deforms in the presence of continuous horizontal air jet. Such a fragmentation typically occurs after the bulk liquid has disintegrated upon exiting the atomizer and is in the form of an ensemble of drops which undergo further breakup. The drop deformation and its eventual disintegration is important in evaluating the efficacy of a particular industrial process, be it combustion in automobile engines or pesticide spraying in agricultural applications. The interplay between competing influences of surface tension and aerodynamic disruptive forces is represented by the Weber number, We, and Ohnesorge number, Oh, and used to describe the breakup morphology. The breakup pattern considered in our study corresponds to that of a bag attached to a toroidal ring which occurs from ∼12 < We < ∼16. We aim to address several issues connected with this breakup process and their dependence on We and Oh which have been hitherto unexplored. The We boundary at which breakup begins is theoretically determined and the expression obtained, We=12(1+2/3Oh{sup 2}), is found to match well with experimental data ([L.-P. Hsiang and G. M. Faeth, Int. J. Multiphase Flow 21(4), 545–560 (1995)] and [R. S. Brodkey, “Formation of drops and bubbles,” in The Phenomena of Fluid Motions (Addison-Wesley, Reading, 1967)]). An exponential growth in the radial extent of the deformed drop and the streamline dimension of the bag is predicted by a theoretical model and confirmed by experimental findings. These quantities are observed to strongly depend on We. However, their dependence on Oh is weak.

  16. Bag breakup of low viscosity drops in the presence of a continuous air jet

    NASA Astrophysics Data System (ADS)

    Kulkarni, V.; Sojka, P. E.

    2014-07-01

    This work examines the breakup of a single drop of various low viscosity fluids as it deforms in the presence of continuous horizontal air jet. Such a fragmentation typically occurs after the bulk liquid has disintegrated upon exiting the atomizer and is in the form of an ensemble of drops which undergo further breakup. The drop deformation and its eventual disintegration is important in evaluating the efficacy of a particular industrial process, be it combustion in automobile engines or pesticide spraying in agricultural applications. The interplay between competing influences of surface tension and aerodynamic disruptive forces is represented by the Weber number, We, and Ohnesorge number, Oh, and used to describe the breakup morphology. The breakup pattern considered in our study corresponds to that of a bag attached to a toroidal ring which occurs from ˜12 < We < ˜16. We aim to address several issues connected with this breakup process and their dependence on We and Oh which have been hitherto unexplored. The We boundary at which breakup begins is theoretically determined and the expression obtained, We = 12( {1 + 2/3 Oh^2 } ), is found to match well with experimental data {[L.-P. Hsiang and G. M. Faeth, Int. J. Multiphase Flow 21(4), 545-560 (1995)] and [R. S. Brodkey, "Formation of drops and bubbles," in The Phenomena of Fluid Motions (Addison-Wesley, Reading, 1967)]}. An exponential growth in the radial extent of the deformed drop and the streamline dimension of the bag is predicted by a theoretical model and confirmed by experimental findings. These quantities are observed to strongly depend on We. However, their dependence on Oh is weak.

  17. Pressure drop reduction and heat transfer deterioration of slush nitrogen in triangular and circular pipe flows

    NASA Astrophysics Data System (ADS)

    Ohira, Katsuhide; Kurose, Kizuku; Okuyama, Jun; Saito, Yutaro; Takahashi, Koichi

    2017-01-01

    Slush fluids such as slush hydrogen and slush nitrogen are characterized by superior properties as functional thermal fluids due to their density and heat of fusion. In addition to allowing efficient hydrogen transport and storage, slush hydrogen can serve as a refrigerant for high-temperature superconducting (HTS) equipment using MgB2, with the potential for synergistic effects. In this study, pressure drop reduction and heat transfer deterioration experiments were performed on slush nitrogen flowing in a horizontal triangular pipe with sides of 20 mm under the conditions of three different cross-sectional orientations. Experimental conditions consisted of flow velocity (0.3-4.2 m/s), solid fraction (0-25 wt.%), and heat flux (0, 10, and 20 kW/m2). Pressure drop reduction became apparent at flow velocities exceeding about 1.3-1.8 m/s, representing a maximum amount of reduction of 16-19% in comparison with liquid nitrogen, regardless of heating. Heat transfer deterioration was seen at flow velocities of over 1.2-1.8 m/s, for a maximum amount of deterioration of 13-16%. The authors of the current study compared the results for pressure drop reduction and heat transfer deterioration in triangular pipe with those obtained previously for circular and square pipes, clarifying differences in flow and heat transfer properties. Also, a correlation equation was obtained between the slush Reynolds number and the pipe friction factor, which is important in the estimation of pressure drop in unheated triangular pipe. Furthermore, a second correlation equation was derived between the modified slush Reynolds number and the pipe friction factor, enabling the integrated prediction of pressure drop in both unheated triangular and circular pipes.

  18. Sinking, wedging, spreading - viscous spreading on a layer of fluid

    NASA Astrophysics Data System (ADS)

    Bergemann, Nico; Juel, Anne; Heil, Matthias

    2016-11-01

    We study the axisymmetric spreading of a sessile drop on a pre-existing layer of the same fluid in a regime where the drop is sufficiently large so that the spreading is driven by gravity while capillary and inertial effects are negligible. Experiments performed with 5 ml drops and layer thicknesses in the range 0.1 mm <= h <= 1 mm show that at long times the radius of the drop evolves as R tn , where the spreading exponent n increases with the layer thickness h. Numerical simulations, based on the axisymmetric free-surface Navier-Stokes equations, reveal three distinct spreading regimes depending on the layer thickness. For thick layers the drop sinks into the layer, accompanied by significant flow in the layer. By contrast, for thin layers the layer ahead of the propagating front is at rest and the spreading behaviour resembles that of a gravity-driven drop spreading on a dry substrate. In the intermediate regime the spreading is characterised by an advancing wedge, which is sustained by fluid flow from the drop into the layer.

  19. Effects of small concentration surfactants on the coalescence of viscous drops

    NASA Astrophysics Data System (ADS)

    Vannozzi, Carolina

    2010-11-01

    Boundary integral simulations, employing Dai and Leal's code [Phys. Fluids 20, 040802 (2008)], are used to study the effects of small concentrations of insoluble surfactants Cs on head-on collisions of two equal-sized viscous drops in a matrix of equal viscosity in a hyperbolic extensional flow, for low Reynolds numbers. The parameters were chosen to mimic the experiments of Yoon et al. [Phys. Fluids 19, 023102 (2007)], which were performed with polymeric drops stabilized by block-copolymer insoluble surfactants in a polymer matrix, where both fluids acted as Newtonian viscous fluids. In these experiments a discontinuous transition in the coalescence process was found for low Cs as the Capillary number Ca was increased. Thus, for Ca>Cac a minimum surfactant concentration exists below which the system behaves like a clean interface system. Here, by varying Cs, i.e. the Marangoni number Ma, and the surface diffusivity, i.e. the interfacial Peclet number Pes, we explain the origin of the transition and its dependence on the parameters. The transition occurs if Pes>Pesc, Ca>Cac and Ma

  20. Modeling Evaporation of Drops of Different Kerosenes

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Harstad, Kenneth

    2007-01-01

    A mathematical model describes the evaporation of drops of a hydrocarbon liquid composed of as many as hundreds of chemical species. The model is intended especially for application to any of several types of kerosenes commonly used as fuels. The concept of continuous thermodynamics, according to which the chemical composition of the evaporating multicomponent liquid is described by use of a probability distribution function (PDF). However, the present model is more generally applicable than is its immediate predecessor.

  1. Diffusion Of Mass In Evaporating Multicomponent Drops

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Harstad, Kenneth G.

    1992-01-01

    Report summarizes study of diffusion of mass and related phenomena occurring in evaporation of dense and dilute clusters of drops of multicomponent liquids intended to represent fuels as oil, kerosene, and gasoline. Cluster represented by simplified mathematical model, including global conservation equations for entire cluster and conditions on boundary between cluster and ambient gas. Differential equations of model integrated numerically. One of series of reports by same authors discussing evaporation and combustion of sprayed liquid fuels.

  2. Impact of water drops on small targets

    NASA Astrophysics Data System (ADS)

    Rozhkov, A.; Prunet-Foch, B.; Vignes-Adler, M.

    2002-10-01

    The collision of water drops against small targets was studied experimentally by means of a high-speed photography technique. The drop impact velocity was about 3.5 m/s. Drop diameters were in the range of 2.8-4.0 mm. The target was a stainless steel disk of 3.9 mm diameter. The drop spread beyond the target like a central cap surrounded by a thin, slightly conical lamella bounded by a thicker rim. By mounting a small obstacle near the target, surface-tension driven Mach waves in the flowing lamella were generated, which are formally equivalent to the familiar compressibility driven Mach waves in gas dynamics. From the measurement of the Mach angle, the values of some flow parameters could be obtained as functions of time, which provided insight into the flow structure. The liquid flowed from the central cap to the liquid rim through the thin lamella at constant momentum flux. At a certain stage of the process, most of the liquid accumulated in the rim and the internal part of the lamella became metastable. In this situation, a rupture wave propagating through the metastable internal part of the lamella caused the rim to retract while forming outwardly directed secondary jets. The jets disintegrated into secondary droplets due to the Savart-Plateau-Rayleigh instability. Prior to the end of the retraction, an internal circular wave of rupture was formed. It originated at the target and then it propagated to meet the retracting rim. Their meeting resulted in a crown of tiny droplets. A theoretical analysis of the ejection process is proposed.

  3. Microfluidic analysis of pressure drop and flow behavior in hypertensive micro vessels.

    PubMed

    Hu, Ruiqing; Li, Fen; Lv, Jiaqi; He, Ying; Lu, Detang; Yamada, Takashi; Ono, Naoki

    2015-01-01

    The retinal arterial network is the only source of the highly nutrient-consumptive retina, thus any insult on the arteries can impair the retinal oxygen and nutrient supply and affect its normal function. The aim of this work is to study the influences of vascular structure variation on the flow and pressure characteristics via microfluidic devices. Two sets of micro-channel were designed to mimic the stenosed microvessels and dichotomous branching structure in the retinal arteries. Three working fluids including red blood cell (RBC) suspension were employed to investigate the pressure drop in the stenosed channel. The flow behaviors of RBC suspensions inside the micro channels were observed using high speed camera system. Pressure drop of different working fluids and RBC velocity profiles in the stenosed channel were obtained. Moreover, hematocrit levels of RBC suspensions inside the bifurcated channels were analyzed from the sequential images of RBC flow. The results of the flow in the stenosed channel show that RBCs drift from the center of the channels, and RBC velocity is influenced not only by the inlet flow rate but also the interaction between RBCs. The measured pressure drops in the stenosed channel increase notably with the increase of fluid viscosity. Furthermore, the dimensionless pressure drop due to the stenosis decreases with Reynolds number. On the other hand, the results of flow through the bifurcated channels show that as the ratio of the daughter-branch width to the mother-channel width increases, the ratio of hematocrit in two connected branches (Ht/Hd) decreases, which is in favorable agreement with the available analysis results.

  4. Dropping In a Microgravity Environment (DIME) Contest

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The first NASA Dropping In a Microgravity Environment (DIME) student competition pilot project came to a conclusion at the Glenn Research Center in April 2001. The competition involved high-school student teams who developed the concept for a microgravity experiment and prepared an experiment proposal. The two student teams - COSI Academy, sponsored by the Columbus Center of Science and Industry, and another team from Cincinnati, Ohio's Sycamore High School, designed a microgravity experiment, fabricated the experimental apparatus, and visited NASA Glenn to operate their experiment in the 2.2 Second Drop Tower. NASA and contractor personnel who conducted the DIME activity with the students. Shown (L-R) are: Daniel Dietrich (NASA) mentor for Sycamore High School team), Carol Hodanbosi (National Center for Microgravity Research; DIME staff), Jose Carrion (GRC Akima, drop tower technician), Dennis Stocker (NASA; DIME staff), Richard DeLombard (NASA; DIME staff), Sandi Thompson (NSMR sabbatical teacher; DIME staff), Peter Sunderland (NCMR, mentor for COSI Academy student team), Adam Malcolm (NASA co-op student; DIME staff). This image is from a digital still camera; higher resolution is not available.

  5. Viscosity Measurement using Drop Coalescence in Microgravity

    NASA Technical Reports Server (NTRS)

    Antar, Basil N.; Ethridge, Edwin; Maxwell, Daniel

    1999-01-01

    We present in here details of a new method, using drop coalescence, for application in microgravity environment for determining the viscosity of highly viscous undercooled liquids. The method has the advantage of eliminating heterogeneous nucleation at container walls caused by crystallization of undercooled liquids during processing. Also, due to the rapidity of the measurement, homogeneous nucleation would be avoided. The technique relies on both a highly accurate solution to the Navier-Stokes equations as well as on data gathered from experiments conducted in near zero gravity environment. The liquid viscosity is determined by allowing the computed free surface shape relaxation time to be adjusted in response to the measured free surface velocity of two coalescing drops. Results are presented from two validation experiments of the method which were conducted recently on board the NASA KC-135 aircraft. In these tests the viscosity of a highly viscous liquid, such as glycerine at different temperatures, was determined to reasonable accuracy using the liquid coalescence method. The experiments measured the free surface velocity of two glycerine drops coalescing under the action of surface tension alone in low gravity environment using high speed photography. The free surface velocity was then compared with the computed values obtained from different viscosity values. The results of these experiments were found to agree reasonably well with the calculated values.

  6. Drop floating on a granular raft

    NASA Astrophysics Data System (ADS)

    Jambon-Puillet, Etienne; Josserand, Christophe; Protiere, Suzie

    2015-11-01

    When a droplet comes in contact with a bath of the same liquid, it coalesces to minimize the surface energy. This phenomenon reduces emulsion stability and is usually fought with surfactant molecules. Another way to slow down coalescence is to use colloidal solid particles. In this case the particles spontaneously migrate to the interface to form ``Pickering'' emulsions and act as a barrier between droplets. Here we use dense, large particles (~ 500 μm) which form a monolayer at an oil/water interface that we call a granular raft. When a droplet is placed on top of such a raft, for a given set of particle properties (contact angle/size), the raft prevents coalescence indefinitely. However, in contrast to what happens when a droplet is placed on a hydrophobic surface and never wets the surface, here the droplet is strongly anchored to the raft and deforms it. We will use this specific configuration to probe the mechanical response of the granular raft: by controlling the droplet volume we can impose tensile or compressive stresses. Finally we will show that the drop, spherical at first, slowly takes a more complex shape as it's volume increases. This shape is not reversible as the drop volume is decreased. The drop can become oblate or prolate with wrinkling of the raft.

  7. Leaf drop affects herbivory in oaks.

    PubMed

    Pearse, Ian S; Karban, Richard

    2013-11-01

    Leaf phenology is important to herbivores, but the timing and extent of leaf drop has not played an important role in our understanding of herbivore interactions with deciduous plants. Using phylogenetic general least squares regression, we compared the phenology of leaves of 55 oak species in a common garden with the abundance of leaf miners on those trees. Mine abundance was highest on trees with an intermediate leaf retention index, i.e. trees that lost most, but not all, of their leaves for 2-3 months. The leaves of more evergreen species were more heavily sclerotized, and sclerotized leaves accumulated fewer mines in the summer. Leaves of more deciduous species also accumulated fewer mines in the summer, and this was consistent with the idea that trees reduce overwintering herbivores by shedding leaves. Trees with a later leaf set and slower leaf maturation accumulated fewer herbivores. We propose that both leaf drop and early leaf phenology strongly affect herbivore abundance and select for differences in plant defense. Leaf drop may allow trees to dispose of their herbivores so that the herbivores must recolonize in spring, but trees with the longest leaf retention also have the greatest direct defenses against herbivores.

  8. Mechanics of couple-stress fluid coatings

    NASA Technical Reports Server (NTRS)

    Waxman, A. M.

    1982-01-01

    The formal development of a theory of viscoelastic surface fluids with bending resistance - their kinematics, dynamics, and rheology are discussed. It is relevant to the mechanics of fluid drops and jets coated by a thin layer of immiscible fluid with rather general rheology. This approach unifies the hydrodynamics of two-dimensional fluids with the mechanics of an elastic shell in the spirit of a Cosserat continuum. There are three distinct facets to the formulation of surface continuum mechanics. Outlined are the important ideas and results associated with each: the kinematics of evolving surface geometries, the conservation laws governing the mechanics of surface continua, and the rheological equations of state governing the surface stress and moment tensors.

  9. Surfactant and nonlinear drop dynamics in microgravity

    NASA Astrophysics Data System (ADS)

    Jankovsky, Joseph Charles

    2000-11-01

    Large amplitude drop dynamics in microgravity were conducted during the second United States Microgravity Laboratory mission carried onboard the Space Shuttle Columbia (20 October-5 November 1995). Centimeter- sized drops were statically deformed by acoustic radiation pressure and released to oscillate freely about a spherical equilibrium. Initial aspect ratios of up to 2.0 were achieved. Experiments using pure water and varying aqueous concentrations of Triton-X 100 and bovine serum albumin (BSA) were performed. The axisymmetric drop shape oscillations were fit using the degenerate spherical shape modes. The frequency and decay values of the fundamental quadrupole and fourth order shape mode were analyzed. Several large amplitude nonlinear oscillation dynamics were observed. Shape entrainment of the higher modes by the fundamental quadrupole mode occurred. Amplitude- dependent effects were observed. The nonlinear frequency shift, where the oscillation frequency is found to decrease with larger amplitudes, was largely unaffected by the presence of surfactants. The percentage of time spent in the prolate shape over one oscillation cycle was found to increase with oscillation amplitude. This prolate shape bias was also unaffected by the addition of surfactants. These amplitude-dependent effects indicate that the nonlinearities are a function of the bulk properties and not the surface properties. BSA was found to greatly enhance the surface viscoelastic properties by increasing the total damping of the oscillation, while Triton had only a small influence on damping. The surface concentration of BSA was found to be diffusion-controlled over the time of the experiments, while the Triton diffusion rate was very rapid. Using the experimental frequency and decay values, the suface viscoelastic properties of surface dilatational viscosity ( ks ) and surface shear viscosity ( ms ) were found for varying surfactant concentrations using the transcendental equation of Lu

  10. Behavior of fluids in a weightless environment

    NASA Technical Reports Server (NTRS)

    Fester, D. A.; Eberhardt, R. N.; Tegart, J. R.

    1977-01-01

    Fluid behavior in a low-g environment is controlled primarily by surface tension forces. Certain fluid and system characteristics determine the magnitude of these forces for both a free liquid surface and liquid in contact with a solid. These characteristics, including surface tension, wettability or contact angle, system geometry, and the relationships governing their interaction, are discussed. Various aspects of fluid behavior in a low-g environment are then presented. This includes the formation of static interface shapes, oscillation and rotation of drops, coalescence, the formation of foams, tendency for cavitation, and diffusion in liquids which were observed during the Skylab fluid mechanics science demonstrations. Liquid reorientation and capillary pumping to establish equilibrium configurations for various system geometries, observed during various free-fall (drop-tower) low-g tests, are also presented. Several passive low-g fluid storage and transfer systems are discussed. These systems use surface tension forces to control the liquid/vapor interface and provide gas-free liquid transfer and liquid-free vapor venting.

  11. Drilling fluid

    SciTech Connect

    Russell, J.A.; Patel, B.B.

    1987-11-03

    A drilling fluid additive mixture is described consisting essentially of a sulfoalkylated tannin in admixture with a non-sulfoalkylated alkali-solubilized lignite wherein the weight ratio of the sulfoalkylated tannin to the non-sulfoalkylated lignite is in the range from about 2:1 to about 1:1. The sulfoalkylated tannin has been sulfoalkylated with at least one -(C(R-)/sub 2/-SO/sub 3/M side chain, wherein each R is selected from the group consisting of hydrogen and alkyl radicals containing from 1 to about 5 carbon atoms, and M is selected from the group consisting of ammonium and the alkali metals.

  12. The Effect of a Yield Stress on the Drainage of the Thin Film Between Two Colliding Newtonian Drops

    NASA Astrophysics Data System (ADS)

    Goel, Sachin; Ramachandran, Arun

    2016-11-01

    Coalescence of drops immersed in fluids possessing a yield stress has been of interest to many industries such as the oil extraction, cosmetics and food industries. Unfortunately, a theoretical understanding of the drainage of the thin film of Bingham fluid (a model yield stress fluid) that develops between two drops undergoing a collision is still lacking, with the exception of two prior studies that make ad-hoc assumptions about the film shape. In this work, we examine this problem via a combination of scaling analysis and numerical simulations based on the lubrication analysis. There are four key features of the film drainage process of Bingham fluids. First, the introduction of a yield stress in the suspending fluid retards the drainage process relative to Newtonian fluid of the same viscosity. Second, the drainage time shows a minimum with respect to the capillary number. Third, the effect of yield stress on the drainage process becomes more pronounced at higher capillary numbers and lower Hamaker constant. Lastly, below a critical height, drainage can be arrested completely due to the yield stress. This critical height scales as τ02R3 τ02R3 γ2 γ2 , where τ0 is the yield stress, R is the drop radius and γ is the interfacial tension, and is, surprisingly, independent of the force colliding the drops. This and other distinguishing characteristics of the drainage process will be elucidated in the presentation.

  13. Ultralow interfacial tensions of aqueous two-phase systems measured using drop shape.

    PubMed

    Atefi, Ehsan; Mann, J Adin; Tavana, Hossein

    2014-08-19

    Aqueous solutions of different polymers can separate and form aqueous two-phase systems (ATPS). ATPS provide an aqueous, biocompatible, and mild environment for separation and fractionation of biomolecules. The interfacial tension between the two aqueous phases plays a major role in ATPS-mediated partition of biomolecules. Because of the structure of the two aqueous phases, the interfacial tensions between the phases can be 3-4 orders of magnitude smaller than conventional fluid-liquid systems: ∼1-100 μJ/m(2) for ATPS compared to ∼72 mJ/m(2) for the water-vapor interface. This poses a major challenge for the experimental measurements of reproducible interfacial tension data for these systems. We address the need for precise determination of ultralow interfacial tensions by systematically studying a series of polymeric ATPS comprising of polyethylene glycol (PEG) and dextran (DEX) as the phase-forming polymers. Sessile and pendant drops of the denser DEX phase are formed within the immersion PEG phase. An axisymmetric drop shape analysis (ADSA) is used to determine interfacial tensions of eight different ATPS. Specific criteria are used to reproducibly determine ultralow interfacial tensions of the ATPS from pendant and sessile drops. Importantly, for a given ATPS, pendant drop and sessile drop experiments return values within 0.001 mJ/m(2) indicating reliability of our measurements. Then, the pendant drop technique is used to measure interfacial tensions of all eight ATPS. Our measured values range from 0.012 ± 0.001 mJ/m(2) to 0.381 ± 0.006 mJ/m(2) and vary with the concentration of polymers in equilibrated phases of ATPS. Measurements of ultralow interfacial tensions with such reproducibility will broadly benefit studies involving partition of different biomolecules in ATPS and elucidate the critical effect of interfacial tension.

  14. Non-linear shape oscillations of rising drops and bubbles: Experiments and simulations

    NASA Astrophysics Data System (ADS)

    Lalanne, Benjamin; Abi Chebel, Nicolas; Vejražka, Jiří; Tanguy, Sébastien; Masbernat, Olivier; Risso, Frédéric

    2015-12-01

    This paper focuses on shape-oscillations of a gas bubble or a liquid drop rising in another liquid. The bubble/drop is initially attached to a capillary and is released by a sudden motion of that capillary, resulting in the rise of the bubble/drop along with the oscillations of its shape. Such experimental conditions make difficult the interpretation of the oscillation dynamics with regard to the standard linear theory of oscillation because (i) amplitude of deformation is large enough to induce nonlinearities, (ii) the rising motion may be coupled with the oscillation dynamics, and (iii) clean conditions without residual surfactants may not be achieved. These differences with the theory are addressed by comparing experimental observation with numerical simulation. Simulations are carried out using Level-Set and Ghost-Fluid methods with clean interfaces. The effect of the rising motion is investigated by performing simulations under different gravity conditions. Using a decomposition of the bubble/drop shape into a series of spherical harmonics, experimental and numerical time evolutions of their amplitudes are compared. Due to large oscillation amplitude, non-linear couplings between the modes are evidenced from both experimental and numerical signals; modes of lower frequency influence modes of higher frequency, whereas the reverse is not observed. Nevertheless, the dominant frequency and overall damping rate of the first five modes are in good agreement with the linear theory. Effect of the rising motion on the oscillations is globally negligible, provided the mean shape of the oscillation remains close to a sphere. In the drop case, despite the residual interface contamination evidenced by a reduction in the terminal velocity, the oscillation dynamics is shown to be unaltered compared to that of a clean drop.

  15. Dynamics of Growth and Breakup of Viscous Pendant Drops into Air.

    PubMed

    Zhang

    1999-04-01

    This paper presents a numerical study of the dynamics of a viscous liquid drop that is being formed directly at the tip of a vertical tube into ambient air. A model is developed to predict the evolution of the drop shape and its breakup based on RIPPLE, which is a solution algorithm for computing transient, two-dimensional, incompressible fluid flow with surface tension on free surfaces of general topology (D. B. Kothe and R. C. Mjolsness, AIAA J. 30, 2694 (1992)). The full Navier-Stokes system is solved by using finite-difference formulation on a Eulerian mesh. The mesh is fixed in space, with the flow and surface moving through it to ensure accurate calculations of complex free surface flows and topology, including surface breakup and coalescence. The novel feature of the numerical algorithm is the use of a Eulerian volume-tracking approach which allows the calculations to pass the breaking point during formation of a drop continuously without interruption or numerical modification and, therefore, to explore the features of generation of satellite droplets. The effects of physical and geometric parameters on the nonlinear dynamics of drop growth and breakup are investigated. The focus here is on drop breakup and subsequent formation of satellite droplets. The effects of finite inertial, capillary, viscous, and gravitational forces are all accounted for to classify different formation dynamics and to elucidate features of satellite droplet generation. The numerical predictions are compared with experimental measurements for water drops, and the results show good agreement. Copyright 1999 Academic Press.

  16. Controlled differential pressure system for an enhanced fluid blending apparatus

    DOEpatents

    Hallman, Jr., Russell Louis

    2009-02-24

    A system and method for producing a controlled blend of two or more fluids. Thermally-induced permeation through a permeable tube is used to mix a first fluid from outside the tube with a second fluid flowing through the tube. Mixture ratios may be controlled by adjusting the temperature of the first fluid or by adjusting the pressure drop through the permeable tube. The combination of a back pressure control valve and a differential regulator is used to control the output pressure of the blended fluid. The combination of the back pressure control valve and differential regulator provides superior flow control of the second dry gas. A valve manifold system may be used to mix multiple fluids, and to adjust the volume of blended fluid produced, and to further modify the mixture ratio.

  17. Modeling pressure drop using generalized scaffold characteristics in an axial-flow bioreactor for soft tissue regeneration.

    PubMed

    Podichetty, Jagdeep T; Bhaskar, Prasana R; Khalf, Abdurizzagh; Madihally, Sundararajan V

    2014-06-01

    The goal of this study was to better understand how analytical permeability models based on scaffold architecture can facilitate a non-invasive technique to real time monitoring of pressure drop in bioreactors. In particular, we evaluated the permeability equations for electrospun and freeze dried scaffolds via pressure drop comparison in an axial-flow bioreactor using computational fluid dynamic (CFD) and experimentation. The polycaprolactone-cellulose acetate fibers obtained by co-axial electrospinning technique and Chitosan-Gelatin scaffolds prepared using freeze-drying techniques were utilized. Initially, the structural properties (fiber size, pore size and porosity) and mechanical properties (elastic modulus and Poisson's ratio) of scaffolds in phosphate buffered saline at 37 °C were evaluated. The CFD simulations were performed by coupling fluid flow, described by Brinkman equation, with structural mechanics using a moving mesh. The experimentally obtained pressure drop values for both 1 mm thick and 2 mm thick scaffolds agreed with simulation results. To evaluate the effect of permeability and elastic modulus on pressure drop, CFD predictions were extended to a broad range of permeabilities spanning synthetic scaffolds and tissues, elastic moduli, and Poisson's ratio. Results indicated an increase in pressure drop with increase in permeability. Scaffolds with higher elastic modulus performed better and the effect of Poisson's ratio was insignificant. Flow induced deformation was negligible in axial-flow bioreactor. In summary, scaffold permeabilities can be calculated using scaffold microarchitecture and can be used in non-invasive monitoring of tissue regeneration.

  18. Tandem wheel drop-legs for standard truck trailer

    NASA Technical Reports Server (NTRS)

    Cantwell, W.; Selstad, R.

    1970-01-01

    Tandem wheel drop-leg device provides a semitrailer with fore and aft mobility that allows it to be moved without a prime mover. The modified drop-legs have trunnion dual wheels and an adjustable brace.

  19. Flow visualization and characterization of evaporating liquid drops

    NASA Technical Reports Server (NTRS)

    Chao, David F. (Inventor); Zhang, Nengli (Inventor)

    2004-01-01

    An optical system, consisting of drop-reflection image, reflection-refracted shadowgraphy and top-view photography, is used to measure the spreading and instant dynamic contact angle of a volatile-liquid drop on a non-transparent substrate. The drop-reflection image and the shadowgraphy is shown by projecting the images of a collimated laser beam partially reflected by the drop and partially passing through the drop onto a screen while the top view photograph is separately viewed by use of a camera video recorder and monitor. For a transparent liquid on a reflective solid surface, thermocapillary convection in the drop, induced by evaporation, can be viewed nonintrusively, and the drop real-time profile data are synchronously recorded by video recording systems. Experimental results obtained from this technique clearly reveal that evaporation and thermocapillary convection greatly affect the spreading process and the characteristics of dynamic contact angle of the drop.

  20. Experimental Investigation of Pendant and Sessile Drops in Microgravity

    NASA Astrophysics Data System (ADS)

    Zhu, Zhi-Qiang; Brutin, David; Liu, Qiu-Sheng; Wang, Yang; Mourembles, Alexandre; Xie, Jing-Chang; Tadrist, Lounes

    2010-09-01

    The experiments regarding the contact angle behavior of pendant and sessile evaporating drops were carried out in microgravity environment. All the experiments were performed in the Drop Tower of Beijing, which could supply about 3.6 s of microgravity (free-fall) time. In the experiments, firstly, drops were injected to create before microgravity. The wettability at different surfaces, contact angles dependance on the surface temperature, contact angle variety in sessile and pendant drops were measured. Different influence of the surface temperature on the contact angle of the drops were found for different substrates. To verify the feasibility of drops creation in microgravity and obtain effective techniques for the forthcoming satellite experiments, we tried to inject liquid to create bigger drop as soon as the drop entering microgravity condition. The contact angle behaviors during injection in microgravity were also obtained.