Bulletin of the American Physical Society
68th Annual Meeting of the APS Division of Fluid Dynamics
Volume 60, Number 21
Sunday–Tuesday, November 22–24, 2015; Boston, Massachusetts
Session R27: Experiments: Particles, Drops, and Bubbles |
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Chair: Jordi Estevadeordad, North Dakota State University Room: 308 |
Tuesday, November 24, 2015 12:50PM - 1:03PM |
R27.00001: Multiple light scattering methods for multiphase flow diagnostics Jordi Estevadeordal Multiphase flows of gases and liquids containing droplets, bubbles, or particulates present light scattering imaging challenges due to the interference from each phase, such as secondary reflections, extinctions, absorptions, and refractions. These factors often prevent the unambiguous detection of each phase and also produce undesired beam steering. The effects can be especially complex in presence of dense phases, multispecies flows, and high pressure environments. This investigation reports new methods for overcoming these effects for quantitative measurements of velocity, density, and temperature fields. The methods are based on light scattering techniques combining Mie and filtered Rayleigh scattering and light extinction analyses and measurements. The optical layout is designed to perform multiple property measurements with improved signal from each phase via laser spectral and polarization characterization, etalon decontamination, and use of multiple wavelengths and imaging detectors. [Preview Abstract] |
Tuesday, November 24, 2015 1:03PM - 1:16PM |
R27.00002: Turbulent crude oil jets in crossflow: holographic measurements of droplet size distributions Xinzhi Xue, David Murphy, Joseph Katz Buoyant, immiscible jets and plumes are created by subsurface oil well blowouts. In this experimental study, high speed visualizations and digital holography follow vertical crude oil turbulent jets of varying Reynolds and Ohnesorge numbers, all falling in the atomization range, while being towed in a towing tank generating `crossflows' at varying crossflow-to-exit speed velocity ratios. The droplet size distributions are measured using a submerged miniature holographic microscopy system, enabling comparison between the plume behavior and the droplet size distributions. Due to variations in rise-velocity with droplet size, the shape and dispersion rate of the plume depends on the interfacial tension. Hence, the crude oil plume rises faster than a `control' miscible oil analog with the same density and viscosity. Premixing the oil with dispersant (Corexit 9500A) at dispersant to oil (DOR) ratios of 1:100 and 1:25 reduces the oil-seawater interfacial tension by up to two orders of magnitude, promoting formation of micro-droplets. Hence, the plume rises at a slower rate, with the large droplets rapidly escaping, leaving smaller ones behind. Furthermore, for the DOR 1:25 case, some of the microdroplets are entrained into the vortices prominent in the wake region under the plume. [Preview Abstract] |
Tuesday, November 24, 2015 1:16PM - 1:29PM |
R27.00003: Confined nanoparticle measurement using Bessel Beam Microscopy Chumki Chakraborty, Craig Snoeyink With the advent of Lab-on-chip technologies, study of near surface phenomenon has gained a lot of importance due to their huge impact on bulk fluid properties. Such studies demand imaging techniques with utmost precision to capture the intricate details of the interface. But, resolution for most of the optical imaging systems is limited due to the light spreading effects of diffraction. This diffraction limited resolution, can be improved by the use of Bessel Beam microscopy. Bessel beam imaging technique when combined with a TIRF (Total Internal Reflection Fluorescence) system can be used for high resolution particle tracking experiments, to reveal detailed information about near surface particle positions and motions with their velocity profile and distribution. With the experimental set up combining these two powerful tools, we plan to present our particle tracking velocimetry results in the interface regime of confined nanoparticles in a binary fluid mixture. Such a study can contribute towards a better understanding of near surface fluid-particle interfaces. [Preview Abstract] |
Tuesday, November 24, 2015 1:29PM - 1:42PM |
R27.00004: Multi-camera PIV imaging in two-phase flow for improved dispersed-phase concentration and velocity calculation Chang Liu, Ken Kiger PIV/PTV has been widely used in making simultaneous measurements of velocity and concentration within multi-phase flows. A major problem confronted by researchers during data processing is to separate the image signals of the dispersed phase from carrier phase reliably and within the same measurement volume. For dilute concentrations, size and brightness criteria have been shown to provide satisfying results in identifying the dispersed phase. However this method is limited to fairly small concentrations due to effects of multiple-scattering and obscuration. To extend this technique, we introduce multi-camera imaging as a means to provide a more precise and reliable identification of the dispersed phase in the face of increased concentration. Specifically, the size-brightness criteria is used to nominally match corresponding dispersed-phase images of the same particle within the other views, and the subsequent out-of-plane position is used to get a more precise 3D location of the particle. In order to demonstrate this method, experiments using static test cell of solid glass sphere suspended in an aqueous gel have been conducted under various concentration and compared to corresponding single camera results. [Preview Abstract] |
Tuesday, November 24, 2015 1:42PM - 1:55PM |
R27.00005: A Method to Improve the Accuracy of Particle Diameter Measurements from Shadowgraph Images Martin A. Erinin, Dan Wang, Xinan Liu, James H. Duncan A method to improve the accuracy of the measurement of the diameter of particles using shadowgraph images is discussed. To obtain data for analysis, a transparent glass calibration reticle, marked with black circular dots of known diameters, is imaged with a high-resolution digital camera using backlighting separately from both a collimated laser beam and diffuse white light. The diameter and intensity of each dot is measured by fitting an inverse hyperbolic tangent function to the particle image intensity map. Using these calibration measurements, a relationship between the apparent diameter and intensity of the dot and its actual diameter and position relative to the focal plane of the lens is determined. It is found that the intensity decreases and apparent diameter increases/decreases (for collimated/diffuse light) with increasing distance from the focal plane. Using the relationships between the measured properties of each dot and its actual size and position, an experimental calibration method has been developed to increase the particle-diameter-dependent range of distances from the focal plane for which accurate particle diameter measurements can be made. [Preview Abstract] |
Tuesday, November 24, 2015 1:55PM - 2:08PM |
R27.00006: Aqueous ammonium thiocyanate solutions as refractive index-matching fluids with low density and viscosity Benjamin C. Morrison, Daniel Borrero-Echeverry Index-matching fluids play an important role in many fluid dynamics experiments, particularly those involving particle tracking, as they can be used to minimize errors due to distortion from the refraction of light across interfaces of the apparatus. Common index-matching fluids, such as sodium iodide solutions or mineral oils, often have densities or viscosities very different from those of water. This can make them undesirable for use as a working fluid when using commercially available tracer particles or at high Reynolds numbers. A solution of ammonium thiocyanate (NH$_4$SCN) can be used for index-matching common materials such as borosilicate glass and acrylic, and has material properties similar to those of water ($\nu \sim 1.6$ cSt and $\rho \sim 1.1$ g/cc). We present an empirical model for predicting the refractive index of aqueous NH$_4$SCN solutions as a function of temperature and NH$_4$SCN concentration that allows experimenters to develop refractive index matching solutions for various common materials. [Preview Abstract] |
Tuesday, November 24, 2015 2:08PM - 2:21PM |
R27.00007: Effect of Polymer Confinement on the Film Drainage Behavior-- An RICM Study Suraj Borkar, Arun Ramchandran We consider the dynamic effects of confinement of macromolecular liquids on the film drainage process between a drop and a flat surface. Under confinement of the order of few molecular length scales, layering and adsorption of long chains of polymers can cause entropic repulsion due to a reduced configurational freedom. This repulsive force can prevent film rupture and lead to the formation of an equilibrium film. In the current work, experiments were conducted with deformable droplets settling under gravity in a suspending liquid for Bond numbers of $O $(10$^{-4})$. The film drainage was studied using a microinterferometric technique namely, Reflection Interference Contrast Microscopy (RICM) for two different systems: a) silicone oil drops in paraffin oil, b) glycerol drops in silicone oil. The RICM analysis for obtaining the film drainage profiles, was done using a combination of simple cosine theory and ray tracing algorithm. For the silicone oil-paraffin oil system, the film drainage behavior observed was as expected from simulations based on thin film drainage equations. On the other hand, glycerol drops of radii smaller than 130 $\mu $m, resulted in the formation of an equilibrium film of silicone oil with an approximate thickness of 10 nm. The origin of this repulsive force is attributed to the presence of an immobilized layer of adsorbed polymer chains. Film drainage observed in glycerol drops of radii larger than 130 $\mu $m, was found to destabilize in a non-axisymmetric mode. The rapid growth of this asymmetric instability can lead to stresses ($O $(100 Pa)) higher than the yield stress of the adsorbed polymer layer. [Preview Abstract] |
Tuesday, November 24, 2015 2:21PM - 2:34PM |
R27.00008: Manipulation of Nano-/Micro Particles Using Light-Actuated Marangoni Tweezers Cunjing Lu, Subramanyan Varanakkottu, Steffen Hardt The ability to manipulate and produce patterns of nano-/micro objects has been of great interest from both a fundamental and an application point of view. Here we demonstrate particle patterning using an optical landscape and optical nanoparticle manipulation based on light-actuated Marangoni tweezers. A liquid film with a photosurfactant which exists in two isomeric states (\textit{cis} and \textit{trans}) is employed for that purpose. Under multiple laser spots created by diffractive optical elements from a He-Cd laser, \textit{cis}-rich regions with higher surface tension than unexposed \textit{trans}-rich regions are created, resulting in converging Marangoni flows directing particles attached to the liquid surface toward the irradiated area. 10 $\mu m$ polystyrene particles and 600 nm $\lambda $-DNA molecules distributed over the liquid surface move to the nearest laser spot and can be arranged in specific patterns. Furthermore, 100 nm polystyrene particles and 20 nm quantum dots can also be trapped, and the 100 nm particles can be driven along quite complex trajectories. Compared to conventional optical tweezers, the corresponding power requirements are much lower. [Preview Abstract] |
Tuesday, November 24, 2015 2:34PM - 2:47PM |
R27.00009: Experimental study on bi-phase flow Air-Oil in Water Emulsion Davide Arnone, Pietro Poesio Bi-phase slug flow oil-in-water emulsion [5\%-20\%] and air through a horizontal pipe (inner diameter 22mm) is experimentally studied. A test with water and air has been performed as comparison. First we create and analyze the flow pattern map to identify slug flow liquid and air inlet conditions. Flow maps are similar for all the used liquid. A video analysis procedure using an high speed camera has been created to obtain all the characteristics of unit slugs: slug velocity, slug length, bubble velocity, bubbles length and slug frequency. We compare translational velocity and frequency with models finding a good agreement. We calculate the pdfs of the lengths to find the correlations between mean values and STD on different air and liquid superficial velocities. We also perform pressure measurements along the pipe. We conclude that the percentage of oil-in- water has no influence on results in terms of velocity, lengths, frequency and pressure drop. [Preview Abstract] |
Tuesday, November 24, 2015 2:47PM - 3:00PM |
R27.00010: A novel technique to control the bubble formation process in a co-flow configuration with planar geometry Javier Ruiz-Rus, Roc\'Io Bola\~{n}os-Jim\'enez, C\'andido Guti\'errez-Montes, Carlos Mart\'Inez-Baz\'an, Alejandro Sevilla We present a novel technique to properly control the bubble formation frequency and size by forcing the water stream in a co-flow configuration with planar geometry through the modulation of the water velocity at the nozzle exit. The main goal of this work is to experimentally explore whether the bubbling regime, which is naturally established for certain values of the water-to-air velocity ratio, $\Lambda = u_w/u_a$, and the Weber number, $We = \rho_{w} u^2_w H_o/\sigma$, can be controlled by the imposed disturbances. A detailed experimental characterization of the forcing effect has been performed by measuring the pressure fluctuations in both the water and the air streams. In addition, the velocity amplitude, which characterizes the process, is obtained. The results show that a minimum disturbance amplitude is needed for an effective control of the bubbling process. Moreover, the process is governed by kinematic non-linear effects, and the position of the maximum deformation is shown to be described through a one-dimensional flow model for the water sheet, based on the exact solution of the Euler equation. [Preview Abstract] |
Tuesday, November 24, 2015 3:00PM - 3:13PM |
R27.00011: Light Attenuation Method for 3D data acquisition (LAM3D) of bottom particle deposits Jenn Wei Er, Adrian W. K. Law, E. Eric Adams, Yang Yang We have developed a novel experimental technique, Light Attenuation Method for 3D data acquisition (LAM3D), to acquire three-dimensional spatial characteristics and temporal development of bottom particle deposits. The new technique performs data acquisition with higher spatial and temporal resolution than existing approaches with laser and ultrasonic 3D profilers, and is therefore ideal for laboratory investigations with fast varying changes in the sediment bed, such as the developing deposition profile from sediment clouds commonly formed during dredging or land reclamation projects and the dynamic evolution in movable bed processes in rivers. The principle of the technique is based on the analysis of the light attenuation due to multiple light scattering through the particle deposits layer compared to the clear water column. With appropriate calibration, the particles size and distribution thickness can be quantified by the transmitted light spectrum. In the presentation, we will first show our measurement setup with a light panel for calibrated illumination and a system of DSLR cameras for the light capturing. Subsequently, we shall present the experimental results of fast evolving deposition profile of a barge-disposed sediment cloud upon its bottom impact on the sea bed. [Preview Abstract] |
Tuesday, November 24, 2015 3:13PM - 3:26PM |
R27.00012: Velocity and size distribution measurement of suspension droplets using PDPA technique Shahin Amiri, Ali Akbarnozari, Christian Moreau, Ali Dolatabadi The creation of fine and uniform droplets from a bulk of liquid is a vital process in a variety of engineering applications, such as atomization in suspension plasma spray (SPS) in which the submicron coating materials are injected to the plasma gas through the suspension droplets. The size and velocity of these droplets has a great impact on the interaction of the suspension with the gas flow emanating from a plasma torch and can consequently affect the mechanical and chemical properties of the resultant coatings. In the current study, an aqueous suspension of small glass particles (2-8 $\mu $m) was atomized by utilizing an effervescent atomizer of 1 mm orifice diameter which involves bubbling gas (air) directly into the liquid stream. The gas to liquid ratio (GLR) was kept constant at 6{\%} throughout this study. The mass concentration of glass particles varied in the range between 0.5 to 5{\%} in order to investigate the effect of suspension viscosity and surface tension on the droplet characteristics, such as velocity and size distributions. These characteristics were simultaneously measured by using a non-intrusive optical technique, Phase Doppler Particle Anemometry (PDPA), which is based on the light signal scattered from the droplets moving in a measurement volume. The velocity and size distribution of suspension droplets were finally compared to those of distilled water under identical conditions. The results showed a different atomization behaviors due to the reduction in surface tension of the suspension spray. [Preview Abstract] |
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