Lee, Shern-Long; Yuan, Zhongyi; Chen, Long; Mali, Kunal S; Müllen, Klaus; De Feyter, Steven
2014-05-28
Controlling crystal polymorphism constitutes a formidable challenge in contemporary chemistry. Two-dimensional (2D) crystals often provide model systems to decipher the complications in 3D crystals. In this contribution, we explore a unique way of governing 2D polymorphism at the organic liquid-solid interface. We demonstrate that a directional solvent flow could be used to stabilize crystalline monolayers of a metastable polymorph. Furthermore, flow fields active within the applied flow generate millimeter-sized domains of either polymorph in a controlled and reproducible fashion. PMID:24867142
Non-equilibrium dynamics of 2D liquid crystals driven by transmembrane gas flow.
Seki, Kazuyoshi; Ueda, Ken; Okumura, Yu-ichi; Tabe, Yuka
2011-07-20
Free-standing films composed of several layers of chiral smectic liquid crystals (SmC*) exhibited unidirectional director precession under various vapor transfers across the films. When the transferred vapors were general organic solvents, the precession speed linearly depended on the momentum of the transmembrane vapors, where the proportional constant was independent of the kind of vapor. In contrast, the same SmC* films under water transfer exhibited precession in the opposite direction. As a possible reason for the rotational inversion, we suggest the competition of two origins for the torques, one of which is microscopic and the other macroscopic. Next, we tried to move an external object by making use of the liquid crystal (LC) motion. When a solid or a liquid particle was set on a film under vapor transfer, the particle was rotated in the same direction as the LC molecules. Using home-made laser tweezers, we measured the force transmitted from the film to the particle, which we found to be several pN. PMID:21709328
Non-equilibrium dynamics of 2D liquid crystals driven by transmembrane gas flow
NASA Astrophysics Data System (ADS)
Seki, Kazuyoshi; Ueda, Ken; Okumura, Yu-ichi; Tabe, Yuka
2011-07-01
Free-standing films composed of several layers of chiral smectic liquid crystals (SmC*) exhibited unidirectional director precession under various vapor transfers across the films. When the transferred vapors were general organic solvents, the precession speed linearly depended on the momentum of the transmembrane vapors, where the proportional constant was independent of the kind of vapor. In contrast, the same SmC* films under water transfer exhibited precession in the opposite direction. As a possible reason for the rotational inversion, we suggest the competition of two origins for the torques, one of which is microscopic and the other macroscopic. Next, we tried to move an external object by making use of the liquid crystal (LC) motion. When a solid or a liquid particle was set on a film under vapor transfer, the particle was rotated in the same direction as the LC molecules. Using home-made laser tweezers, we measured the force transmitted from the film to the particle, which we found to be several pN.
NASA Astrophysics Data System (ADS)
Wang, Teng
2016-02-01
This paper is concerned with the strong solutions to the Cauchy problem of a simplified Ericksen-Leslie system of compressible nematic liquid crystals in two or three dimensions with vacuum as far field density. For strong solutions, some a priori decay rate (in large time) for the pressure, the spatial gradient of velocity field and the second spatial gradient of liquid crystal director field are obtained provided that the initial total energy is suitably small. Furthermore, with the help of the key decay rates, we establish the global existence and uniqueness of strong solutions (which may be of possibly large oscillations) in two spatial dimensions.
Flow past 2-D Hemispherical Rigid Canopies
NASA Astrophysics Data System (ADS)
Carnasciali, Maria-Isabel
2013-11-01
The flow past a 2-dimensional rigid hemispherical shape is investigated using PIV. Flow field measurements and images were generated with the use of a Thermoflow® apparatus. Results of this study are compared to prior work (APS DFD 2012 Session E9.00003) which employed CFD to investigate the flow in the near wake of hemispherical parachutes. The various sized gaps/open areas were positioned at distinct locations. The work presented here is part of a larger research project to investigate flow fields in deceleration devices and parachutes. Understanding the pitch-stability of parachutes is essential for accurate design and implementation of these deceleration devices but they present a difficult system to analyze. The flexibility of the parachute fabric results in large variations in the parachute geometry leading to complex fluid-structure interactions. Such flow, combined with flow through gaps and open areas, has been postulated to shed alternating vortices causing pitching/oscillations of the canopy. The results presented provide some insight into which geometric features affect vortex shedding and may enable the redesign of the baseline parachute to minimize instabilities.
Mean flow and anisotropic cascades in decaying 2D turbulence
NASA Astrophysics Data System (ADS)
Liu, Chien-Chia; Cerbus, Rory; Gioia, Gustavo; Chakraborty, Pinaki
2015-11-01
Many large-scale atmospheric and oceanic flows are decaying 2D turbulent flows embedded in a non-uniform mean flow. Despite its importance for large-scale weather systems, the affect of non-uniform mean flows on decaying 2D turbulence remains unknown. In the absence of mean flow it is well known that decaying 2D turbulent flows exhibit the enstrophy cascade. More generally, for any 2D turbulent flow, all computational, experimental and field data amassed to date indicate that the spectrum of longitudinal and transverse velocity fluctuations correspond to the same cascade, signifying isotropy of cascades. Here we report experiments on decaying 2D turbulence in soap films with a non-uniform mean flow. We find that the flow transitions from the usual isotropic enstrophy cascade to a series of unusual and, to our knowledge, never before observed or predicted, anisotropic cascades where the longitudinal and transverse spectra are mutually independent. We discuss implications of our results for decaying geophysical turbulence.
The 2d MIT: The Pseudogap and Fermi Liquid Theory
NASA Astrophysics Data System (ADS)
Castner, T. G.
2005-06-01
Fermi liquid theory for the 2d metal-insulator transition is extended to include the correlation gap in the density-of-states. The results are consistent with the scaling form g=gce[on(To/T)] at T larger than a characteristic T* ∝ xTc (Tc=Ec= mobility edge). The two-component model n1+nloc=n=nc(1+x) for n>nc is required and the theory explains the T-dependence of the data of Hanein et al. for p-type GaAs.
A discrete simulation of 2-D fluid flow on TERASYS
Mullins, P.G.; Krolak, P.D.
1995-12-01
A discrete simulation of two-dimensional (2-D) fluid flow, on a recently designed novel architecture called TERASYS is presented. The simulation uses a cellular automaton approach, implemented in a new language called data-parallel bit C (dbC). A performance comparison between our implementation on TERASYS and an implementation on the Connection Machine is discussed. We comment briefly on the suitability of the TERASYS system for modeling fluid flow using cellular automata.
Hierarchical streamline bundles for visualizing 2D flow fields.
Shene, Ching-Kuang; Wang, Chaoli; Yu, Hongfeng; Chen, Jacqueline H.
2010-08-01
We present hierarchical streamline bundles, a new approach to simplifying and visualizing 2D flow fields. Our method first densely seeds a flow field and produces a large number of streamlines that capture important flow features such as critical points. Then, we group spatially neighboring and geometrically similar streamlines to construct a hierarchy from which we extract streamline bundles at different levels of detail. Streamline bundles highlight multiscale flow features and patterns through a clustered yet non-cluttered display. This selective visualization strategy effectively accentuates visual foci and therefore is able to convey the desired insight into the flow fields. The hierarchical streamline bundles we have introduced offer a new way to characterize and visualize the flow structure and patterns in multiscale fashion. Streamline bundles highlight critical points clearly and concisely. Exploring the hierarchy allows a complete visualization of important flow features. Thanks to selective streamline display and flexible LOD refinement, our multiresolution technique is scalable and is promising for viewing large and complex flow fields. In the future, we would like to seek a cost-effective way to generate streamlines without enforcing the dense seeding condition. We will also extend this approach to handle real-world 3D complex flow fields.
Advecting Procedural Textures for 2D Flow Animation
NASA Technical Reports Server (NTRS)
Kao, David; Pang, Alex; Moran, Pat (Technical Monitor)
2001-01-01
This paper proposes the use of specially generated 3D procedural textures for visualizing steady state 2D flow fields. We use the flow field to advect and animate the texture over time. However, using standard texture advection techniques and arbitrary textures will introduce some undesirable effects such as: (a) expanding texture from a critical source point, (b) streaking pattern from the boundary of the flowfield, (c) crowding of advected textures near an attracting spiral or sink, and (d) absent or lack of textures in some regions of the flow. This paper proposes a number of strategies to solve these problems. We demonstrate how the technique works using both synthetic data and computational fluid dynamics data.
Mesophases in nearly 2D room-temperature ionic liquids.
Manini, N; Cesaratto, M; Del Pópolo, M G; Ballone, P
2009-11-26
Computer simulations of (i) a [C(12)mim][Tf(2)N] film of nanometric thickness squeezed at kbar pressure by a piecewise parabolic confining potential reveal a mesoscopic in-plane density and composition modulation reminiscent of mesophases seen in 3D samples of the same room-temperature ionic liquid (RTIL). Near 2D confinement, enforced by a high normal load, as well as relatively long aliphatic chains are strictly required for the mesophase formation, as confirmed by computations for two related systems made of (ii) the same [C(12)mim][Tf(2)N] adsorbed at a neutral solid surface and (iii) a shorter-chain RTIL ([C(4)mim][Tf(2)N]) trapped in the potential well of part i. No in-plane modulation is seen for ii and iii. In case ii, the optimal arrangement of charge and neutral tails is achieved by layering parallel to the surface, while, in case iii, weaker dispersion and packing interactions are unable to bring aliphatic tails together into mesoscopic islands, against overwhelming entropy and Coulomb forces. The onset of in-plane mesophases could greatly affect the properties of long-chain RTILs used as lubricants. PMID:19886615
Topological phase transition in 2D porous media flows
NASA Astrophysics Data System (ADS)
Waisbord, Nicolas; Stoop, Norbert; Kantsler, Vasily; Guasto, Jeffrey S.; Dunkel, Jorn; Guasto Team; Dunkel Team; Kantsler Team
2015-11-01
Since the establishment of Darcy's law, analysis of porous-media flows has focused primarily on linking macroscopic transport properties, such as mean flow rate and dispersion, to the pore statistics of the material matrix. Despite intense efforts to understand the fluid velocity statistics from the porous-media structure, a qualitative and quantitative connection remains elusive. Here, we combine precisely controlled experiments with theory to quantify how geometric disorder in the matrix affects the flow statistics and transport in a quasi-2D microfluidic channel. Experimentally measured velocity fields for a range of different microstructure configurations are found to be in excellent agreement with large-scale numerical simulations. By successively increasing the matrix disorder, we study the transition from periodic flow structures to transport networks consisting of extended high-velocity channels. Morse-Smale complex analysis of the flow patterns reveals a topological phase transition that is linked to a qualitative change in the physical transport properties. This work demonstrates that topological flow analysis provides a mathematically well-defined, broadly applicable framework for understanding and quantifying fluid transport in complex geometries.
Experimental and Computational Study of Multiphase Flow Hydrodynamics in 2D Trickle Bed Reactors
NASA Astrophysics Data System (ADS)
Nadeem, H.; Ben Salem, I.; Kurnia, J. C.; Rabbani, S.; Shamim, T.; Sassi, M.
2014-12-01
Trickle bed reactors are largely used in the refining processes. Co-current heavy oil and hydrogen gas flow downward on catalytic particle bed. Fine particles in the heavy oil and/or soot formed by the exothermic catalytic reactions deposit on the bed and clog the flow channels. This work is funded by the refining company of Abu Dhabi and aims at mitigating pressure buildup due to fine deposition in the TBR. In this work, we focus on meso-scale experimental and computational investigations of the interplay between flow regimes and the various parameters that affect them. A 2D experimental apparatus has been built to investigate the flow regimes with an average pore diameter close to the values encountered in trickle beds. A parametric study is done for the development of flow regimes and the transition between them when the geometry and arrangement of the particles within the porous medium are varied. Liquid and gas flow velocities have also been varied to capture the different flow regimes. Real time images of the multiphase flow are captured using a high speed camera, which were then used to characterize the transition between the different flow regimes. A diffused light source was used behind the 2D Trickle Bed Reactor to enhance visualizations. Experimental data shows very good agreement with the published literature. The computational study focuses on the hydrodynamics of multiphase flow and to identify the flow regime developed inside TBRs using the ANSYS Fluent Software package. Multiphase flow inside TBRs is investigated using the "discrete particle" approach together with Volume of Fluid (VoF) multiphase flow modeling. The effect of the bed particle diameter, spacing, and arrangement are presented that may be used to provide guidelines for designing trickle bed reactors.
Corbino Disk Viscometer for 2D Quantum Electron Liquids
NASA Astrophysics Data System (ADS)
Tomadin, Andrea; Vignale, Giovanni; Polini, Marco
2014-12-01
The shear viscosity of a variety of strongly interacting quantum fluids, ranging from ultracold atomic Fermi gases to quark-gluon plasmas, can be accurately measured. On the contrary, no experimental data exist, to the best of our knowledge, on the shear viscosity of two-dimensional quantum electron liquids hosted in a solid-state matrix. In this work we propose a Corbino disk device, which allows a determination of the viscosity of a quantum electron liquid from the dc potential difference that arises between the inner and the outer edge of the disk in response to an oscillating magnetic flux.
Corbino disk viscometer for 2D quantum electron liquids.
Tomadin, Andrea; Vignale, Giovanni; Polini, Marco
2014-12-01
The shear viscosity of a variety of strongly interacting quantum fluids, ranging from ultracold atomic Fermi gases to quark-gluon plasmas, can be accurately measured. On the contrary, no experimental data exist, to the best of our knowledge, on the shear viscosity of two-dimensional quantum electron liquids hosted in a solid-state matrix. In this work we propose a Corbino disk device, which allows a determination of the viscosity of a quantum electron liquid from the dc potential difference that arises between the inner and the outer edge of the disk in response to an oscillating magnetic flux. PMID:25526137
Field Evaluation of a Novel 2D Preferential Flow Snowpack Hydrology Model
NASA Astrophysics Data System (ADS)
Leroux, N.; Pomeroy, J. W.; Kinar, N. J.
2015-12-01
Accurate estimation of snowmelt flux is of primary importance for runoff hydrograph prediction, which is used for water management and flood forecasting. Lateral flows and preferential flow pathways in porous media flow have proven critical for improving soil and groundwater flow models, but though many physically-based layered snowmelt models have been developed, only 1D matrix flow is accounted for in these models. Therefore, there is a need for snowmelt models that include these processes so as to examine the potential to improve snowmelt hydrological modelling. A 2D model is proposed that enables an improved understanding of energy and water flows within deep heterogeneous snowpacks, including those on slopes. A dual pathway theory is presented that simulates the formation of preferential flow paths, vertical and lateral water flows through the snow matrix and flow fingers, internal energy fluxes, melt, wet snow metamorphism, and internal refreezing. The dual pathway model utilizes an explicit finite volume method to solve for the energy and water flux equations over a non-orthogonal grid. It was run and evaluated using in-situ data collected from snowpit - accessed gravimetric, thermometric, photographic, and dielectric observations and novel non-invasive acoustic observations of layering, temperature, flowpath geometry, density and wetness at the Fortress Mountain Snow Laboratory, Alberta, Canada. The melt of a natural snowpack was artificially generated after detailed observation of snowpack initial conditions such as snow layer properties, temperature, and liquid water content. Snowpack ablation and liquid water content distribution over time were then measured and used for model parameterization and validation. Energy available at the snow surface and soil slope angle were set as mondel inputs. Model verification was based on snowpack property evolution. The heterogeneous flow model can be an important tool to help understand snowmelt flow processes, how
Rapid Plateau border size variations expected in three simple experiments on 2D liquid foams.
Gay, C; Rognon, P; Reinelt, D; Molino, F
2011-01-01
Up to a global scaling, the geometry of foams squeezed between two solid plates (2D GG foams) essentially depends on two independent parameters: the liquid volume fraction and the degree of squeezing (bubble thickness to diameter ratio). We describe it in two main asymptotic regimes: fully dry floor tiles, where the Plateau border radius is smaller than the distance between the solid plates, and dry pancakes, where it is larger. We predict a rapid variation of the Plateau border radius in one part of the pancake regime, namely when the Plateau border radius is larger than the inter-plate distance but smaller than the geometric mean of that distance and the bubble perimeter. This rapid variation is not related to any topological change in the foam: in all the regimes we consider, the bubbles remain in mutual lateral contact through films located at mid-height between both plates. We provide asymptotic predictions in different types of experiments on such 2D GG foams: when foam is being progressively dried or wetted, when it is being squeezed further or stretched, when it coarsens through film breakage or through inter-bubble gas diffusion. Our analysis is restricted to configurations close to equilibrium, as we do not include stresses resulting from bulk viscous flow or from non-homogeneous surfactant concentrations. We also assume that the inter-plate distance is sufficiently small for gravity to be negligible. The present work does not provide a method for measuring small Plateau border radii experimentally, but it indicates that large (and easily observable) Plateau borders should appear or disappear rather suddenly in some types of experiments with small inter-plate gaps. It also gives expected orders of magnitude that should be helpful for designing experiments on 2D GG foams. PMID:21253804
2D vortex interaction in a non-uniform flow
NASA Astrophysics Data System (ADS)
Perrot, Xavier; Carton, X.
2010-03-01
In a two-dimensional incompressible fluid, we study the interaction of two like-signed Rankine vortices embedded in a steady shear/strain flow. The numerical results of vortex evolutions are compared with the analytical results for point vortices. We show the existence of vortex equilibria, and of merger for initial distances larger than those without external flow. The evolutions depend on the initial orientation of the vortices in the external flow.
Active interrogation of plasma-liquid boundary using 2D plasma-in-liquid apparatus
NASA Astrophysics Data System (ADS)
Lai, Janis; Foster, John
2015-09-01
Plasma medicine and plasma-based water purification technologies rely on the production and transport of plasma-derived (direct or indirect) reactive species into the bulk medium. This interaction takes place at the interface between the gas phase plasma and the liquid medium. The nature of radical production and subsequent radical transport from this region or boundary layer is not well understood due to the difficulty of implementing diagnostics to interrogate this region. We present a 2-D plasma-in-liquid water apparatus that makes the interface region assessable to optical diagnostics. Using colorimetric chemical probes, acidification and oxidation fronts are tracked using high-speed imaging and spectroscopy. Additionally, observed, plasma-induced fluid dynamical effects are also discussed. Forces at the interface can play a key role in the transport of radicals into the bulk solution. The role of plasma-driven interfacial forces as well as that of the applied, local electric field on chemical front propagation velocity and induced circulation are also discussed. Supported by grants NSF CBET 1336375 and DOE DE-SC0001939.
Improvement of a 2D numerical model of lava flows
NASA Astrophysics Data System (ADS)
Ishimine, Y.
2013-12-01
I propose an improved procedure that reduces an improper dependence of lava flow directions on the orientation of Digital Elevation Model (DEM) in two-dimensional simulations based on Ishihara et al. (in Lava Flows and Domes, Fink, JH eds., 1990). The numerical model for lava flow simulations proposed by Ishihara et al. (1990) is based on two-dimensional shallow water model combined with a constitutive equation for a Bingham fluid. It is simple but useful because it properly reproduces distributions of actual lava flows. Thus, it has been regarded as one of pioneer work of numerical simulations of lava flows and it is still now widely used in practical hazard prediction map for civil defense officials in Japan. However, the model include an improper dependence of lava flow directions on the orientation of DEM because the model separately assigns the condition for the lava flow to stop due to yield stress for each of two orthogonal axes of rectangular calculating grid based on DEM. This procedure brings a diamond-shaped distribution as shown in Fig. 1 when calculating a lava flow supplied from a point source on a virtual flat plane although the distribution should be circle-shaped. To improve the drawback, I proposed a modified procedure that uses the absolute value of yield stress derived from both components of two orthogonal directions of the slope steepness to assign the condition for lava flows to stop. This brings a better result as shown in Fig. 2. Fig. 1. (a) Contour plots calculated with the original model of Ishihara et al. (1990). (b) Contour plots calculated with a proposed model.
COYOTE: A computer program for 2-D reactive flow simulations
Cloutman, L.D.
1990-04-01
We describe the numerical algorithm used in the COYOTE two- dimensional, transient, Eulerian hydrodynamics program for reactive flows. The program has a variety of options that provide capabilities for a wide range of applications, and it is designed to be robust and relatively easy to use while maintaining adequate accuracy and efficiency to solve realistic problems. It is based on the ICE method, and it includes a general species and chemical reaction network for simulating reactive flows. It also includes swirl, turbulence transport models, and a nonuniform mesh capability. We describe several applications of the program. 33 refs., 4 figs.
2D VARIABLY SATURATED FLOWS: PHYSICAL SCALING AND BAYESIAN ESTIMATION
A novel dimensionless formulation for water flow in two-dimensional variably saturated media is presented. It shows that scaling physical systems requires conservation of the ratio between capillary forces and gravity forces. A direct result of this finding is that for two phys...
2D Mixed Convection Thermal Incompressible Viscous Flows
NASA Astrophysics Data System (ADS)
Bermudez, Blanca; Nicolas, Alfredo
2005-11-01
Mixed convection thermal incomprressible viscous fluid flows in rectangular cavities are presented. These kind of flows may be governed by the time-dependent Boussinesq approximation in terms of the stream function-vorticity variables formulation. The results are obtained with a simple numerical scheme based mainly on a fixed point iterative process applied to the non-linear system of elliptic equations that is obtained after a second order time discretization. Numerical experiments are reported for the problem of a cavity with fluid boundary motion on the top. Some results correspond to validation examples and others, to the best of our knowledge, correspond to new results. To show that the new results are correct, a mesh size and time independence studies are carried out, and the acceptable errors are measured point-wise. For the optimal mesh size and time step the final times when the steady state is reached, as solution from the unsteady problem, are reported; it should be seen that they are larger than the ones for natural convection which, physically speaking, show the agreement that mixed convection flows are more active than those of natural convection due to the fluid boundary motion on the top of the cavity. The flow parameters are: the Reynolds number, the Grashof number and the aspect ratio.
NASA Technical Reports Server (NTRS)
Fabris, Gracio
1994-01-01
Improved devices mix gases and liquids into bubbly or foamy flows. Generates flowing, homogeneous foams or homogeneous dispersions of small, noncoalescing bubbles entrained in flowing liquids. Mixers useful in liquid-metal magnetohydrodynamic electric-power generator, froth flotation in mining industry, wastewater treatment, aerobic digestion, and stripping hydrocarbon contaminants from ground water.
Lagrangian statistics and flow topology in forced 2-D turbulence
Kadoch, B.; Del-Castillo-Negrete, Diego B; Bos, W.J.T.; Schneider, Kai
2011-01-01
A study of the relationship between Lagrangian statistics and flow topology in fluid turbulence is presented. The topology is characterized using the Weiss criterion, which provides a conceptually simple tool to partition the flow into topologically different regions: elliptic (vortex dominated), hyperbolic (deformation dominated), and intermediate (turbulent background). The flow corresponds to forced two-dimensional Navier-Stokes turbulence in doubly periodic and circular bounded domains, the latter with no-slip boundary conditions. In the double periodic domain, the probability density function (pdf) of the Weiss field exhibits a negative skewness consistent with the fact that in periodic domains the flow is dominated by coherent vortex structures. On the other hand, in the circular domain, the elliptic and hyperbolic regions seem to be statistically similar. We follow a Lagrangian approach and obtain the statistics by tracking large ensembles of passively advected tracers. The pdfs of residence time in the topologically different regions are computed introducing the Lagrangian Weiss field, i.e., the Weiss field computed along the particles' trajectories. In elliptic and hyperbolic regions, the pdfs of the residence time have self-similar algebraic decaying tails. In contrast, in the intermediate regions the pdf has exponential decaying tails. The conditional pdfs (with respect to the flow topology) of the Lagrangian velocity exhibit Gaussian-like behavior in the periodic and in the bounded domains. In contrast to the freely decaying turbulence case, the conditional pdfs of the Lagrangian acceleration in forced turbulence show a comparable level of intermittency in both the periodic and the bounded domains. The conditional pdfs of the Lagrangian curvature are characterized, in all cases, by self-similar power-law behavior with a decay exponent of order - 2.
Shen, Jianfeng; Wu, Jingjie; Wang, Man; Dong, Pei; Xu, Jingxuan; Li, Xiaoguang; Zhang, Xiang; Yuan, Junhua; Wang, Xifan; Ye, Mingxin; Vajtai, Robert; Lou, Jun; Ajayan, Pulickel M
2016-05-01
A proper design of direct liquid phase exfoliation (LPE) for 2D materials as graphene, MoS2 , WS2 , h-BN, Bi2 Se3 , MoSe2 , SnS2 , and TaS2 with common cosolvents is carried out based on considering the polar and dispersive components of surface tensions of various cosolvents and 2D materials. It has been found that the exfoliation efficiency is enhanced by matching the ratio of surface tension components of cosolvents to that of the targeted 2D materials, based on which common cosolvents composed of IPA/water, THF/water, and acetone/water can be designed for sufficient LPE process. In this context, the library of low-toxic and low-cost solvents with low boiling points for LPE is infinitely enlarged when extending to common cosolvents. Polymer-based composites reinforced with a series of different 2D materials are compared with each other. It is demonstrated that the incorporation of cosolvents-exfoliated 2D materials can substantially improve the mechanical and thermal properties of polymer matrices. Typically, with the addition of 0.5 wt% of such 2D material as MoS2 nanosheets, the tensile strength and Young's modulus increased up to 74.85% and 136.97%, respectively. The different enhancement effect of 2D materials is corresponded to the intrinsic properties and LPE capacity of 2D materials. PMID:27059403
NASA Technical Reports Server (NTRS)
Kapoor, Kamlesh; Anderson, Bernhard H.; Shaw, Robert J.
1994-01-01
A two-dimensional computational code, PRLUS2D, which was developed for the reactive propulsive flows of ramjets and scramjets, was validated for two-dimensional shock-wave/turbulent-boundary-layer interactions. The problem of compression corners at supersonic speeds was solved using the RPLUS2D code. To validate the RPLUS2D code for hypersonic speeds, it was applied to a realistic hypersonic inlet geometry. Both the Baldwin-Lomax and the Chien two-equation turbulence models were used. Computational results showed that the RPLUS2D code compared very well with experimentally obtained data for supersonic compression corner flows, except in the case of large separated flows resulting from the interactions between the shock wave and turbulent boundary layer. The computational results compared well with the experiment results in a hypersonic NASA P8 inlet case, with the Chien two-equation turbulence model performing better than the Baldwin-Lomax model.
Schefer, Alexandre B; Braumann, Ulrich; Tseng, Li-Hong; Spraul, Manfred; Soares, Marisi G; Fernandes, João B; da Silva, Maria F G F; Vieira, Paulo C; Ferreira, Antonio G
2006-09-22
Separation and characterization of limonoids from Switenia macrophylla (Meliaceae) by HPLC-NMR technique has been described. Analyses were carried out using reversed-phase gradient HPLC elution coupled to NMR (600 MHz) spectrometer in stopped-flow mode. Separated peaks were collected into an interface unit prior to NMR measurements, which were performed with suppression of solvent signals by shaped pulses sequences. Structure elucidation of the limonoids was attained by data obtained from 1H NMR, TOCSY, gHSQC and gHMBC spectra without conventional isolation that is usually applied in natural products studies. PMID:16904679
A multispeed Discrete Boltzmann Model for transcritical 2D shallow water flows
NASA Astrophysics Data System (ADS)
La Rocca, Michele; Montessori, Andrea; Prestininzi, Pietro; Succi, Sauro
2015-03-01
In this work a Discrete Boltzmann Model for the solution of transcritical 2D shallow water flows is presented and validated. In order to provide the model with transcritical capabilities, a particular multispeed velocity set has been employed for the discretization of the Boltzmann equation. It is shown that this particular set naturally yields a simple and closed procedure to determine higher order equilibrium distribution functions needed to simulate transcritical flow. The model is validated through several classical benchmarks and is proven to correctly and accurately simulate both 1D and 2D transitions between the two flow regimes.
2D-simulation of wet steam flow in a steam turbine with spontaneous condensation
NASA Astrophysics Data System (ADS)
Sun, Lan-Xin; Zheng, Qun; Liu, Shun-Long
2007-06-01
Removal of condensates from wet steam flow in the last stages of steam turbines significantly promotes stage efficiency and prevents erosion of rotors. In this paper, homogeneous spontaneous condensation in transonic steam flow in the 2-D rotor-tip section of a stage turbine is investigated. Calculated results agree with experimental data reasonably well. On the basis of the above work, a 2-D numerical simulation of wet steam flow in adjacent root sections of a complex steam turbine stage was carried out. Computational results were analyzed and provide insights into effective removal of humidity.
Fluctuating Pressure Data from 2-D Nozzle Cold Flow Tests (Dual Bell)
NASA Technical Reports Server (NTRS)
Nesman, Tomas E.
2001-01-01
Rocket engines nozzle performance changes as a vehicle climbs through the atmosphere. An altitude compensating nozzle, ACN, is intended to improve on a fixed geometry bell nozzle that performs at optimum at only one trajectory point. In addition to nozzle performance, nozzle transient loads are an important consideration. Any nozzle experiences large transient toads when shocks pass through the nozzle at start and shutdown. Additional transient toads will occur at transitional flow conditions. The objectives of cold flow nozzle testing at MSFC are CFD benchmark / calibration and Unsteady flow / sideloads. Initial testing performed with 2-D inserts to 14" transonic wind tunnel. Recent review of 2-D data in preparation for nozzle test facility 3-D testing. This presentation shows fluctuating pressure data and some observations from 2-D dual-bell nozzle cold flow tests.
Two dimensional spectroscopy of Liquids in THz-domain: THz analogue of 2D Raman spectroscopy
NASA Astrophysics Data System (ADS)
Okumura, K.; Tanimura, Y.
1998-03-01
After the initial proposal(Y. Tanimura and S. Mukamel, J. Chem. Phys. 99, 9496 (1993)), the two dimensional Raman spectroscopy in the liquid phase has been received a considerable attention. Both experimental and theoretical activity of this field has been quite high. Since we have two controllable delay times, we can obtain more information than the lower-order experiments such as OKE. The new information includes that on heterogeneous distribution in liquids. Recently, it is found that the coupling between the modes in liquids can be investigated by the technique, both experimentally and theoretically(A. Tokmakoff, M.J. Lang, D.S. Larsen, G.R. Fleming, V. Chernyak, and S. Mukamel, Phys. Rev. Lett. (in press))^,(K. Okumura and Y. Tanimura, Chem. Phys. Lett. 278, 175 (1997)) In this talk, we will emphasize that we can perform the THz analogue of the 2D Raman spectroscopy if the THz short-pulse laser becomes available, which may not be in the far future. Theoretically, we can formulate this novel THz spectroscopy on the same footing as the 2D Raman spectroscopy. We will clarify new aspects of this technique comparing with the 2D Raman spectroscopy--- the reason it worth trying the tough experiment. See
NASA Astrophysics Data System (ADS)
Zou, B.; Li, D. F.; Hu, H. J.; Zhang, H. W.; Lou, L. H.; Chen, M.; Lv, Z. Y.
Based on the verified two dimensional(2D) finite element model for river flow simulation, the effect of estuary training levees on the water flow and sediment movement in the Yellow River estuary is analyzed. For disclosing the effect of setting the two training levees on the flow and sediment motion, the calculation and analysis for the two projects, (one is no levees, the other is setting up two no levees) are given. The results show that when setting up two training levees, water flow is bound by levees and the water flows become more concentrated. As a result, velocity increases in the main channel, sediment carrying capacity of water flow increases correspondingly.
Liquid scintillator for 2D dosimetry for high-energy photon beams
Poenisch, Falk; Archambault, Louis; Briere, Tina Marie; Sahoo, Narayan; Mohan, Radhe; Beddar, Sam; Gillin, Michael T.
2009-05-15
Complex radiation therapy techniques require dosimetric verification of treatment planning and delivery. The authors investigated a liquid scintillator (LS) system for application for real-time high-energy photon beam dosimetry. The system was comprised of a transparent acrylic tank filled with liquid scintillating material, an opaque outer tank, and a CCD camera. A series of images was acquired when the tank with liquid scintillator was irradiated with a 6 MV photon beam, and the light data measured with the CCD camera were filtered to correct for scattering of the optical light inside the liquid scintillator. Depth-dose and lateral profiles as well as two-dimensional (2D) dose distributions were found to agree with results from the treatment planning system. Further, the corrected light output was found to be linear with dose, dose rate independent, and is robust for single or multiple acquisitions. The short time needed for image acquisition and processing could make this system ideal for fast verification of the beam characteristics of the treatment machine. This new detector system shows a potential usefulness of the LS for 2D QA.
NASA Astrophysics Data System (ADS)
Li, Y.; Kazemifar, F.; Blois, G.; Christensen, K. T.
2015-12-01
Multiphase flow of water and supercritical carbon dioxide (CO2) in porous media is central to geological sequestration of CO2 into saline aquifers. However, our fundamental understanding of the coupled flow dynamics of CO2 and water in complex geologic media still remains limited, especially at the pore scale. Recently, studies have been carried out in 2D homogeneous models with the micro-PIV technique, yielding very interesting observations of pore-scale flow transport. The primary aim of this work is to leverage this experimental protocol to quantify the pore-scale flow of water and liquid/supercritical CO2 in 2D heterogeneous porous micromodels under reservoir-relevant conditions. The goal is to capture the dynamics of this multi-phase flow in a porous matrix that mimics the heterogeneity of natural rock. Fluorescent microscopy and the micro-PIV technique are employed to simultaneously measure the spatially-resolved instantaneous velocity field in the water and quantify the instantaneous spatial configuration of both phases. The results for heterogeneous micromodels will be presented and compared with those for homogeneous micromodels, yielding valuable insight into flow processes at the pore scale in natural rock.
An F2D analysis of the Flow Instability Test (FIT) experiment
Suo-Anttila, A.
1993-10-01
The F2D code was used to analyze the Flow-Instability-Test (FIT) experiments at Brookhaven National Laboratories. A one-dimensional analysis of the experiment indicated that at the higher temperature levels the element should be unstable. The experimental data corroborated this theory. The two-dimensional simulation behaved in a manner that was very similar to the experimentally measured behavior. In conclusion, the FIT experimental analysis yields partial code validation of F2D, and it also validates the methodology that is used in analyzing thermal flow stability.
High-resistance liquid-crystal lens array for rotatable 2D/3D autostereoscopic display.
Chang, Yu-Cheng; Jen, Tai-Hsiang; Ting, Chih-Hung; Huang, Yi-Pai
2014-02-10
A 2D/3D switchable and rotatable autostereoscopic display using a high-resistance liquid-crystal (Hi-R LC) lens array is investigated in this paper. Using high-resistance layers in an LC cell, a gradient electric-field distribution can be formed, which can provide a better lens-like shape of the refractive-index distribution. The advantages of the Hi-R LC lens array are its 2D/3D switchability, rotatability (in the horizontal and vertical directions), low driving voltage (~2 volts) and fast response (~0.6 second). In addition, the Hi-R LC lens array requires only a very simple fabrication process. PMID:24663563
CAS2D- NONROTATING BLADE-TO-BLADE, STEADY, POTENTIAL TRANSONIC CASCADE FLOW ANALYSIS CODE
NASA Technical Reports Server (NTRS)
Dulikravich, D. S.
1994-01-01
An exact, full-potential-equation model for the steady, irrotational, homoentropic, and homoenergetic flow of a compressible, inviscid fluid through a two-dimensional planar cascade together with its appropriate boundary conditions has been derived. The CAS2D computer program numerically solves an artificially time-dependent form of the actual full-potential-equation, providing a nonrotating blade-to-blade, steady, potential transonic cascade flow analysis code. Comparisons of results with test data and theoretical solutions indicate very good agreement. In CAS2D, the governing equation is discretized by using type-dependent, rotated finite differencing and the finite area technique. The flow field is discretized by providing a boundary-fitted, nonuniform computational mesh. This mesh is generated by using a sequence of conformal mapping, nonorthogonal coordinate stretching, and local, isoparametric, bilinear mapping functions. The discretized form of the full-potential equation is solved iteratively by using successive line over relaxation. Possible isentropic shocks are captured by the explicit addition of an artificial viscosity in a conservative form. In addition, a four-level, consecutive, mesh refinement feature makes CAS2D a reliable and fast algorithm for the analysis of transonic, two-dimensional cascade flows. The results from CAS2D are not directly applicable to three-dimensional, potential, rotating flows through a cascade of blades because CAS2D does not consider the effects of the Coriolis force that would be present in the three-dimensional case. This program is written in FORTRAN IV for batch execution and has been implemented on an IBM 370 series computer with a central memory requirement of approximately 200K of 8 bit bytes. The CAS2D program was developed in 1980.
Extension and application of the Preissmann slot model to 2D transient mixed flows
NASA Astrophysics Data System (ADS)
Maranzoni, Andrea; Dazzi, Susanna; Aureli, Francesca; Mignosa, Paolo
2015-08-01
This paper presents an extension of the Preissmann slot concept for the modeling of highly transient two-dimensional (2D) mixed flows. The classic conservative formulation of the 2D shallow water equations for free surface flows is adapted by assuming that two fictitious vertical slots, aligned along the two Cartesian plane directions and normally intersecting, are added on the ceiling of each integration element. Accordingly, transitions between free surface and pressurized flow can be handled in a natural and straightforward way by using the same set of governing equations. The opportunity of coupling free surface and pressurized flows is actually useful not only in one-dimensional (1D) problems concerning sewer systems but also for modeling 2D flooding phenomena in which the pressurization of bridges, culverts, or other crossing hydraulic structures can be expected. Numerical simulations are performed by using a shock-capturing MUSCL-Hancock finite volume scheme combined with the FORCE (First-Order Centred) solver for the evaluation of the numerical fluxes. The validation of the mathematical model is accomplished on the basis of both exact solutions of 1D discontinuous initial value problems and reference radial solutions of idealized test cases with cylindrical symmetry. Furthermore, the capability of the model to deal with practical field-scale applications is assessed by simulating the transit of a bore under an arch bridge. Numerical results show that the proposed model is suitable for the prediction of highly transient 2D mixed flows.
Combination 3D TOP with 2D PC MRA Techique for cerebral blood flow volume measurement.
Guo, G; Wu, R H; Zhang, Y P; Guan, J T; Guo, Y L; Cheng, Y; terBrugge, K; Mikulis, D J
2006-01-01
To demonstrate the discrepancy of cerebral blood flow volume (BFV) estimation with 2D phase-contrast (2D PC) MRA guided with 3D time-of-flight (3D TOF) MR localization by using an "internal" standard. 20 groups of the common (CCA), internal (ICA), and external (ECA) carotid arteries in 10 healthy subjects were examined with 2D PC MRA guided by 3D TOF MR angiograms. The sum BFV of the internal and external carotid arteries was then compared with the ipsilateral common carotid artery flow. An accurate technique would demonstrate no difference. The difference was therefore a measure of accuracy of the method. 3D TOF MRA localization is presented to allow the determination of a slice orientation to improve the accuracy of 2D PC MRA in estimate the BFV. By using the combined protocols, there was better correlation in BFV estimate between the sum of ICA+ECA with the ipsilateral CCA (R2=0.729, P=0.000). The inconsistency (mean +/- SD) was found to be 6.95 +/- 5.95% for estimate the BFV in ICA+ECA and ipsilateral CCA. The main inconsistency was contributed to the ECA and its branches. Guided with 3D TOF MRA localization, 2D PC MRA is more accurate in the determination of blood flow volume in the carotid arteries. PMID:17946401
The oscillatory motion of a surfactant-laden liquid plug in a 2D-channel
NASA Astrophysics Data System (ADS)
Fujioka, Hideki; Grotberg, James B.
2004-11-01
Liquid plugs can form in the lung's small airways near the end of expiration. This happens more frequently when the amount of pulmonary surfactant is reduced. In medical treatments such as surfactant replacement therapy, partial liquid ventilation, and drug delivery, the formation of plugs in an airway is important to deliver the instilled liquid uniformly throughout the lung. In this study, we investigate numerically the oscillatory motion of a surfactant-laden liquid plug within a two-dimensional channel lined by a thin liquid film. The viscosity of both the left and right air phases is assumed to be negligible, so that the only fluid dynamics of the liquid phase is considered. The plug motion is regulated by the flow rate in the left air phase, which is prescribed as a sinusoidal function of time. The pressure drop between the left and right air phases varies for time with a different phase of the flow rate. The plug length and the film thickness oscillate with an average value during a cycle. These behaviors changes by system parameters, Reynolds number, Womersley number, Capillary number, and surfactant properties. The significance of this study on mechanical stresses acting on airway epithelial cells caused by the motion of a liquid plug during normal breath, conventional or high-frequency ventilation is discussed. Supported by NIH grant HL41126, NASA grant NAG3-2740.
Use of finite volume radiation for predicting the Knudsen minimum in 2D channel flow
Malhotra, Chetan P.; Mahajan, Roop L.
2014-12-09
In an earlier paper we employed an analogy between surface-to-surface radiation and free-molecular flow to model Knudsen flow through tubes and onto planes. In the current paper we extend the analogy between thermal radiation and molecular flow to model the flow of a gas in a 2D channel across all regimes of rarefaction. To accomplish this, we break down the problem of gaseous flow into three sub-problems (self-diffusion, mass-motion and generation of pressure gradient) and use the finite volume method for modeling radiation through participating media to model the transport in each sub-problem as a radiation problem. We first model molecular self-diffusion in the stationary gas by modeling the transport of the molecular number density through the gas starting from the analytical asymptote for free-molecular flow to the kinetic theory limit of gaseous self-diffusion. We then model the transport of momentum through the gas at unit pressure gradient to predict Poiseuille flow and slip flow in the 2D gas. Lastly, we predict the generation of pressure gradient within the gas due to molecular collisions by modeling the transport of the forces generated due to collisions per unit volume of gas. We then proceed to combine the three radiation problems to predict flow of the gas over the entire Knudsen number regime from free-molecular to transition to continuum flow and successfully capture the Knudsen minimum at Kn ∼ 1.
Evaluation of 2D shallow-water model for spillway flow with a complex geometry
Technology Transfer Automated Retrieval System (TEKTRAN)
Although the two-dimensional (2D) shallow water model is formulated based on several assumptions such as hydrostatic pressure distribution and vertical velocity is negligible, as a simple alternative to the complex 3D model, it has been used to compute water flows in which these assumptions may be ...
Parallelized CCHE2D flow model with CUDA Fortran on Graphics Process Units
Technology Transfer Automated Retrieval System (TEKTRAN)
This paper presents the CCHE2D implicit flow model parallelized using CUDA Fortran programming technique on Graphics Processing Units (GPUs). A parallelized implicit Alternating Direction Implicit (ADI) solver using Parallel Cyclic Reduction (PCR) algorithm on GPU is developed and tested. This solve...
Application of a generalized minimal residual method to 2D unsteady flows
NASA Technical Reports Server (NTRS)
Hixon, Ray; Sankar, L. N.
1992-01-01
A generalized minimum residual scheme (GMRES), previously developed for solving nonlinear and linear systems of equations, has been applied to the numerical solution of 2D unsteady compressible flows. It is found that the use of GMRES significantly increases the time step that may be used, compared to noniterative implicit schemes. The feasibility of reducing the memory requirements of the GMRES scheme using a multigrid strategy has also been explored. Several sample steady and unsteady viscous flow applications are presented.
2D and 3D Histioid Disclination Networks in Liquid Crystals
NASA Astrophysics Data System (ADS)
Jiang, Miao; Guo, Yubing; Lavrentovich, Oleg; Wei, Qi-Huo
Topological defects and disclination lines are of both fundamental interest and practical importance. In this paper, we will show that periodic/non-periodic 2D/3D networks of disclination lines can be created in nematic liquid crystal cells by setting well-designed alignment patterns at the top and bottom substrate surfaces. The desired complex patterns of liquid crystal molecular alignments at the substrates are obtained using a projection photoalignment technique based on plasmonic metamasks. The designs of alignment patterns and their resulting disclination line networks will be presented. These designable topological networks represent a new kind of artificial materials which could be of useful for directing colloidal and molecular assembly. National Science Foundation CMMI-1436565.
Fukuto, M.; Kewalramani, S.; Wang, S.; Lin, Y.; Nguyen, G.; Wang, Q.; Yang, L.
2011-02-07
We report an experimental demonstration of a strategy for inducing two-dimensional (2D) crystallization of charged nanoparticles on oppositely charged fluid interfaces. This strategy aims to maximize the interfacial adsorption of nanoparticles, and hence their lateral packing density, by utilizing a combination of weakly charged particles and a high surface charge density on the planar interface. In order to test this approach, we investigated the assembly of cowpea mosaic virus (CPMV) on positively charged lipid monolayers at the aqueous solution surface, by means of in situ X-ray scattering measurements at the liquid-vapor interface. The assembly was studied as a function of the solution pH, which was used to vary the charge on CPMV, and of the mole fraction of the cationic lipid in the binary lipid monolayer, which set the interface charge density. The 2D crystallization of CPMV occurred in a narrow pH range just above the particle's isoelectric point, where the particle charge was weakly negative, and only when the cationic-lipid fraction in the monolayer exceeded a threshold. The observed 2D crystals exhibited nearly the same packing density as the densest lattice plane within the known 3D crystals of CPMV. The above electrostatic approach of maximizing interfacial adsorption may provide an efficient route to the crystallization of nanoparticles at aqueous interfaces.
Observation of 2D Ising criticality of liquid-gas transition by the flowgram method
NASA Astrophysics Data System (ADS)
Yarmolinsky, Max; Kuklov, Anatoly
We study the critical properties of the transition in 2D liquid-gas system with the square-well potential interaction by Monte Carlo simulations in the grand canonical ensemble. Due to lack of the underlying Ising symmetry, the analysis cannot be done reliably by the standard methods applicable to lattice systems. In contrast, the analysis based on the flowgram method allowed us to find the critical point to significantly higher (and controllable) accuracy than in previous studies by other authors. Simulations were performed in a progression of sizes L up to size L = 84 , with the particle numbers varying over 3 orders of magnitude and the subcritical behavior not extending beyond L = 10 - 15 . The finite size scaling analysis of the critical exponents and their ratio, μ and γ / ν , gives values consistent with the 2D Ising universality class within 1-2% of errors. Our result essentially closes proposals that the nature of the liquid-gas transition might be different from the Ising model in systems with short-range interactions. This work was supported by the NSF Grant PHY1314469.
Simulation of the flow and mass transfer for KDP crystals undergoing 2D translation during growth
NASA Astrophysics Data System (ADS)
Zhou, Chuan; Li, Mingwei; Hu, Zhitao; Yin, Huawei; Wang, Bangguo; Cui, Qidong
2016-09-01
In this study, a novel motion mode for crystals during growth, i.e., 2D translation, is proposed. Numerical simulations of flow and mass transfer are conducted for the growth of large-scale potassium dihydrogen phosphate (KDP) crystals subjected to the new motion mode. Surface supersaturation and shear stress are obtained as functions of the translational velocity, distance, size, orientation of crystals. The dependence of these two parameters on the flow fields around the crystals is also discussed. The thicknesses of the solute boundary layer varied with translational velocity are described. The characteristics of solution flow and surface supersaturation distribution are summarized, where it suggests that the morphological stability of a crystal surface can be enhanced if the proposed 2D translation is applied to crystal growth.
Approximate analytic solutions to 3D unconfined groundwater flow within regional 2D models
NASA Astrophysics Data System (ADS)
Luther, K.; Haitjema, H. M.
2000-04-01
We present methods for finding approximate analytic solutions to three-dimensional (3D) unconfined steady state groundwater flow near partially penetrating and horizontal wells, and for combining those solutions with regional two-dimensional (2D) models. The 3D solutions use distributed singularities (analytic elements) to enforce boundary conditions on the phreatic surface and seepage faces at vertical wells, and to maintain fixed-head boundary conditions, obtained from the 2D model, at the perimeter of the 3D model. The approximate 3D solutions are analytic (continuous and differentiable) everywhere, including on the phreatic surface itself. While continuity of flow is satisfied exactly in the infinite 3D flow domain, water balance errors can occur across the phreatic surface.
Investigation of flow rate in a quasi-2D hopper with two symmetric outlets
NASA Astrophysics Data System (ADS)
Zhang, Xuezhi; Zhang, Sheng; Yang, Guanghui; Lin, Ping; Tian, Yuan; Wan, Jiang-Feng; Yang, Lei
2016-03-01
In this study the flow rate in a quasi-2D hopper with two symmetric outlets was investigated numerically. When two outlets merge into one, the flow rate is obviously bigger than that with a large enough distance between them. To explain the influence of the interaction between these two outlets, it was found that the velocity field above one outlet will be affected by the neighboring outlet by reducing the stagnant zone. With increasing distance, this interaction becomes weaker. Finally the formula of flow rate considering various outlet sizes and distances is fitted to the simulation data.
Turbulent flow over a surface-mounted 2-D block in thermally-stratified boundary layers
NASA Astrophysics Data System (ADS)
Zhang, W.; Markfort, C. D.; Porte-Agel, F.
2013-12-01
Turbulent boundary-layer flows over complex topography have been of great interest in the atmospheric sciences and wind engineering communities. The geometry of the topography, surface characteristics and atmospheric thermal stability play important roles in determining momentum and scalar flux distribution. Studies of turbulent flow over simplified topography, such as 2-D or 3-D blocks and 2-D or 3-D sinusoidal hills, conducted under neutrally stratified boundary-layer conditions have provided insightful information of fluid dynamics. However, atmospheric thermal stability has rarely been incorporated into laboratory simulations, in particular, wind-tunnel experiments. Extension of such studies in thermally-stratified wind tunnels will fill this gap and advance our understanding of the underlying physics of flow over complex topography. Additionally, experimental data are useful for the development of new parameterizations for surface fluxes and validation of numerical models such as Large-Eddy Simulation (LES). A series of experiments involving neutral and thermally-stratified boundary-layer flows over a surface-mounted 2-D block, conducted at the Saint Anthony Falls Laboratory boundary-layer wind tunnel, will be presented. The 2-D block, with a width to height ratio of 2:1, occupied the lowest 25% of the turbulent boundary layer. Thermal stratification of the boundary layer was achieved by independently controlling the temperature of both the airflow, the test section floor and block surfaces. Measurements using high-resolution PIV, x-wire/cold-wire anemometry, thermal-couples and surface heat flux sensors were made to identify and quantify the turbulent flow properties, including the size of the recirculation zone, coherent vortex structures and the subsequent boundary layer recovery. Emphasis will be put on addressing thermal stability effects on momentum and scalar flux distribution.
Investigation of the effect of wall friction on the flow rate in 2D and 3D Granular Flow
NASA Astrophysics Data System (ADS)
Carballo-Ramirez, Brenda; Pleau, Mollie; Easwar, Nalini; Birwa, Sumit; Shah, Neil; Tewari, Shubha
We have measured the mass flow rate of spherical steel spheres under gravity in vertical, straight-walled 2 and 3-dimensional hoppers, where the flow velocity is controlled by the opening size. Our measurements focus on the role of friction and its placement along the walls of the hopper. In the 2D case, an increase in the coefficient of static friction from μ = 0.2 to 0.6 is seen to decrease the flow rate significantly. We have changed the placement of frictional boundaries/regions from the front and back walls of the 2D hopper to the side walls and floor to investigate the relative importance of the different regions in determining the flow rate. Fits to the Beverloo equation show significant departure from the expected exponent of 1.5 in the case of 2D flow. In contrast, 3D flow rates do not show much dependence on wall friction and its placement. We compare the experimental data to numerical simulations of gravity driven hopper granular flow with varying frictional walls constructed using LAMMPS*. *http://lammps.sandia.gov Supported by NSF MRSEC DMR 0820506.
Moment Invariants for 2D Flow Fields via Normalization in Detail.
Bujack, Roxana; Hotz, Ingrid; Scheuermann, Gerik; Hitzer, Eckhard
2015-08-01
The analysis of 2D flow data is often guided by the search for characteristic structures with semantic meaning. One way to approach this question is to identify structures of interest by a human observer, with the goal of finding similar structures in the same or other datasets. The major challenges related to this task are to specify the notion of similarity and define respective pattern descriptors. While the descriptors should be invariant to certain transformations, such as rotation and scaling, they should provide a similarity measure with respect to other transformations, such as deformations. In this paper, we propose to use moment invariants as pattern descriptors for flow fields. Moment invariants are one of the most popular techniques for the description of objects in the field of image recognition. They have recently also been applied to identify 2D vector patterns limited to the directional properties of flow fields. Moreover, we discuss which transformations should be considered for the application to flow analysis. In contrast to previous work, we follow the intuitive approach of moment normalization, which results in a complete and independent set of translation, rotation, and scaling invariant flow field descriptors. They also allow to distinguish flow features with different velocity profiles. We apply the moment invariants in a pattern recognition algorithm to a real world dataset and show that the theoretical results can be extended to discrete functions in a robust way. PMID:26357255
Integrated Coupling of Surface and Subsurface Flow with HYDRUS-2D
NASA Astrophysics Data System (ADS)
Hartmann, Anne; Šimůnek, Jirka; Wöhling, Thomas; Schütze, Niels
2016-04-01
Describing interactions between surface and subsurface flow processes is important to adequately define water flow in natural systems. Since overland flow generation is highly influenced by rainfall and infiltration, both highly spatially heterogeneous processes, overland flow is unsteady and varies spatially. The prediction of overland flow needs to include an appropriate description of the interactions between the surface and subsurface flow. Coupling surface and subsurface water flow is a challenging task. Different approaches have been developed during the last few years, each having its own advantages and disadvantages. A new approach by Weill et al. (2009) to couple overland flow and subsurface flow based on a generalized Richards equation was implemented into the well-known subsurface flow model HYDRUS-2D (Šimůnek et al., 2011). This approach utilizes the one-dimensional diffusion wave equation to model overland flow. The diffusion wave model is integrated in HYDRUS-2D by replacing the terms of the Richards equation in a pre-defined runoff layer by terms defining the diffusion wave equation. Using this approach, pressure and flux continuity along the interface between both flow domains is provided. This direct coupling approach provides a strong coupling of both systems based on the definition of a single global system matrix to numerically solve the coupled flow problem. The advantage of the direct coupling approach, compared to the loosely coupled approach, is supposed to be a higher robustness, when many convergence problems can be avoided (Takizawa et al., 2014). The HYDRUS-2D implementation was verified using a) different test cases, including a direct comparison with the results of Weill et al. (2009), b) an analytical solution of the kinematic wave equation, and c) the results of a benchmark test of Maxwell et al. (2014), that included several known coupled surface subsurface flow models. Additionally, a sensitivity analysis evaluating the effects
Optimization and Design of 2d Honeycomb Lattice Photonic Crystal Modulated by Liquid Crystals
NASA Astrophysics Data System (ADS)
Guo, Caihong; Zheng, Jihong; Gui, Kun; Zhang, Menghua; Zhuang, Songlin
2013-12-01
Photonic crystals (PCs) with infiltrating liquid crystals (LCs) have many potential applications because of their ability to continuously modulate the band-gaps. Using the plane-wave expansion method (PWM), we simulate the band-gap distribution of 2D honeycomb lattice PC with different pillar structures (circle, hexagonal and square pillar) and with different filling ratios, considering both when the LC is used as filling pillar material and semiconductors (Si, Ge) are used in the substrate, and when the semiconductors (Si, Ge) are pillar material and the LC is the substrate. Results show that unlike LC-based triangle lattice PC, optimized honeycomb lattice PC has the ability to generate absolute photonic band-gaps for fabricating optical switches. We provide optimization parameters for LC infiltrating honeycomb lattice PC structure based on simulation results and analysis.
Determining Transition State Geometries in Liquids Using 2D-IR
Harris, Charles; Cahoon, James F.; Sawyer, Karma R.; Schlegel, Jacob P.; Harris, Charles B.
2007-12-11
Many properties of chemical reactions are determined by the transition state connecting reactant and product, yet it is difficult to directly obtain any information about these short-lived structures in liquids. We show that two-dimensional infrared (2D-IR) spectroscopy can provide direct information about transition states by tracking the transformation of vibrational modes as a molecule crossed a transition state. We successfully monitored a simple chemical reaction, the fluxional rearrangement of Fe(CO)5, in which the exchange of axial and equatorial CO ligands causes an exchange of vibrational energy between the normal modes of the molecule. This energy transfer provides direct evidence regarding the time scale, transition state, and mechanism of the reaction.
Effective Temperature of 2D Dusty Plasma Liquids at the Discrete Level
Io, C.-W.; Chan, C.-L.; I Lin
2007-07-13
Fluctuation-dissipation theory has been used to measure the effective temperature of non-equilibrium system. In this work, using a 2D dusty plasma liquid formed by the negatively charged fine particles suspending in weakly ionized discharges and sheared by two CW counter parallel laser beams, we measure the micro-transport at the kinetic level. The effective temperatures Teff at different time scales are obtained through the Stokes-Einstein relation which relates the diffusion coefficient (D) and the viscosity ({eta}). The external energy is cascaded from the slow hopping modes to the fast caging modes through mutual coupling, which leads to the higher effective temperature of the slow hopping modes.
Flow Quantification from 2D Phase Contrast MRI in Renal Arteries Using Clustering
NASA Astrophysics Data System (ADS)
Zöllner, Frank G.; Monnsen, Jan Ankar; Lundervold, Arvid; Rørvik, Jarle
We present an approach based on clustering to segment renal arteries from 2D PC Cine MR images to measure blood velocity and flow. Such information are important in grading renal artery stenosis and support the decision on surgical interventions like percutan transluminal angioplasty. Results show that the renal arteries could be extracted automatically and the corresponding velocity profiles could be calculated. Furthermore, the clustering could detect possible phase wrap effects automatically as well as differences in the blood flow patterns within the vessel.
Eulerian and Lagrangian methods for vortex tracking in 2D and 3D flows
NASA Astrophysics Data System (ADS)
Huang, Yangzi; Green, Melissa
2014-11-01
Coherent structures are a key component of unsteady flows in shear layers. Improvement of experimental techniques has led to larger amounts of data and requires of automated procedures for vortex tracking. Many vortex criteria are Eulerian, and identify the structures by an instantaneous local swirling motion in the field, which are indicated by closed or spiral streamlines or pathlines in a reference frame. Alternatively, a Lagrangian Coherent Structures (LCS) analysis is a Lagrangian method based on the quantities calculated along fluid particle trajectories. In the current work, vortex detection is demonstrated on data from the simulation of two cases: a 2D flow with a flat plate undergoing a 45 ° pitch-up maneuver and a 3D wall-bounded turbulence channel flow. Vortices are visualized and tracked by their centers and boundaries using Γ1, the Q criterion, and LCS saddle points. In the cases of 2D flow, saddle points trace showed a rapid acceleration of the structure which indicates the shedding from the plate. For channel flow, saddle points trace shows that average structure convection speed exhibits a similar trend as a function of wall-normal distance as the mean velocity profile, and leads to statistical quantities of vortex dynamics. Dr. Jeff Eldredge and his research group at UCLA are gratefully acknowledged for sharing the database of simulation for the current research. This work was supported by the Air Force Office of Scientific Research under AFOSR Award No. FA9550-14-1-0210.
Thermal stability effects on the separated flow over a steep 2-D hill
NASA Astrophysics Data System (ADS)
Zhang, W.; Porte-Agel, F.
2012-12-01
Transport of momentum and scalars in turbulent boundary-layer flows over complex topography has been of great interest in the atmospheric sciences and wind engineering communities. Applications include but are not limited to weather forecasting, air pollution dispersion, aviation safety control, and wind energy project planning. Linear models have been well accepted to predict boundary-layer flows over topography with gentle slope. However, once the slope of the topography is sufficientlyo steep that flow separation occurs, linear models are not applicable. Modeling the turbulent transport of momentum and scalars in such flows has to be achieved through non-linear models, such as Reynolds-averaged Navier-Stokes solvers and large-eddy simulations (LES). Dynamics of the separated boundary-layer flows over steep topography is affected by the shape and size of the topography, surface characteristics (e.g., roughness and temperature) and atmospheric thermal stability. Most wind-tunnel experiments of boundary-layer flows over idealized topography (e.g. 2-D or 3-D hills, axisymmetric bumps) do not take thermal stability effects into account due to difficulty of physical simulation. We conducted comprehensive experimental investigation of stably- and unstably- stratified boundary layers over a steep 2-D hill in the thermally-controlled boundary-layer wind tunnel at the Saint Anthony Falls Laboratory. The 2-D model hill has a steepest slope of 0.73 and its shape follows a cosine square function: h=Hcos^2 (πx/L) for -L/2 ≤ x ≤ L/2 , where the maximum height H is 7 cm and the total width L is 15 cm. High-resolution Particle Image Velocimetry (PIV) provides dynamic information of the separated shear layer, the recirculation zone and flow reattachment. Turbulent momentum and scalar (heat) fluxes were characterized up to the top of the thermal boundary layer using a triple-wire (cross-wire and cold-wire) anemometer. Results indicate that promoted and suppressed turbulence
Free surface and flow problem for a viscous liquid
Zaytsev, M. L. Akkerman, V. B.
2011-10-15
An exact closed system of equations is proposed for describing the shape of the free surface of a viscous steady-state liquid in the 2D case in terms of the surface itself. A method that lowers the dimensionality in the Navier-Stokes equation is demonstrated, and its application in problems of steady-state flow past solids is considered.
Instability of plasma waves during relaxation of 2D turbulent flows
NASA Astrophysics Data System (ADS)
Kabantsev, A. A.; Drsicoll, C. F.
2015-11-01
We observe strong excitation of novel low-frequency z-dependent plasma waves (mθ = 0 ,kz = 1) , occurring during the nominally 2D relaxation of turbulent initial conditions (10 -100 interacting vortices) in strongly magnetized electron columns. This initial relaxation often results in ``2D vortex crystal'' states. Here we describe experiments showing the concomitant growth of ill-understood low-frequency plasma waves, probably due to ``leakage'' of 2D turbulent potential energy into z-dependent fluctuations. With plasma injection, the lowest regular Trivelpiece- Gould mode (mθ = 0 ,kz = 1) is observed at fTG (t) ~ 2 . 8 MHz and exponential decay time τTG ~ 1 msec. Also, we observe rapid exponential growth of a novel low-frequency mode with fLF (t) ~ 0 . 3 MHz, nominally also with mθ = 0 ,kz = 1 . In a few milliseconds (several tens of rotation times at B = 10kG), the LF-mode becomes highly nonlinear, developing up to a dozen temporal harmonics. When a LF-harmonic resonates with the decaying TG-mode, LF-mode energy is transferred into the TG-mode, and both modes remain at moderate amplitudes until the 2D turbulent relaxation abates (hundreds of rotation times). The ill-understood fLF is independent of B, even though the growth and duration times follow scale as B1 from the 2D flows. Supported by National Science Foundation Grant PHY-1414570, Department of Energy Grants DE-SC0008693.
TRENT2D WG: a smart web infrastructure for debris-flow modelling and hazard assessment
NASA Astrophysics Data System (ADS)
Zorzi, Nadia; Rosatti, Giorgio; Zugliani, Daniel; Rizzi, Alessandro; Piffer, Stefano
2016-04-01
Mountain regions are naturally exposed to geomorphic flows, which involve large amounts of sediments and induce significant morphological modifications. The physical complexity of this class of phenomena represents a challenging issue for modelling, leading to elaborate theoretical frameworks and sophisticated numerical techniques. In general, geomorphic-flows models proved to be valid tools in hazard assessment and management. However, model complexity seems to represent one of the main obstacles to the diffusion of advanced modelling tools between practitioners and stakeholders, although the UE Flood Directive (2007/60/EC) requires risk management and assessment to be based on "best practices and best available technologies". Furthermore, several cutting-edge models are not particularly user-friendly and multiple stand-alone software are needed to pre- and post-process modelling data. For all these reasons, users often resort to quicker and rougher approaches, leading possibly to unreliable results. Therefore, some effort seems to be necessary to overcome these drawbacks, with the purpose of supporting and encouraging a widespread diffusion of the most reliable, although sophisticated, modelling tools. With this aim, this work presents TRENT2D WG, a new smart modelling solution for the state-of-the-art model TRENT2D (Armanini et al., 2009, Rosatti and Begnudelli, 2013), which simulates debris flows and hyperconcentrated flows adopting a two-phase description over a mobile bed. TRENT2D WG is a web infrastructure joining advantages offered by the software-delivering model SaaS (Software as a Service) and by WebGIS technology and hosting a complete and user-friendly working environment for modelling. In order to develop TRENT2D WG, the model TRENT2D was converted into a service and exposed on a cloud server, transferring computational burdens from the user hardware to a high-performing server and reducing computational time. Then, the system was equipped with an
A fast and accurate method to predict 2D and 3D aerodynamic boundary layer flows
NASA Astrophysics Data System (ADS)
Bijleveld, H. A.; Veldman, A. E. P.
2014-12-01
A quasi-simultaneous interaction method is applied to predict 2D and 3D aerodynamic flows. This method is suitable for offshore wind turbine design software as it is a very accurate and computationally reasonably cheap method. This study shows the results for a NACA 0012 airfoil. The two applied solvers converge to the experimental values when the grid is refined. We also show that in separation the eigenvalues remain positive thus avoiding the Goldstein singularity at separation. In 3D we show a flow over a dent in which separation occurs. A rotating flat plat is used to show the applicability of the method for rotating flows. The shown capabilities of the method indicate that the quasi-simultaneous interaction method is suitable for design methods for offshore wind turbine blades.
CAS2D: FORTRAN program for nonrotating blade-to-blade, steady, potential transonic cascade flows
NASA Technical Reports Server (NTRS)
Dulikravich, D. S.
1980-01-01
An exact, full-potential-equation (FPE) model for the steady, irrotational, homentropic and homoenergetic flow of a compressible, homocompositional, inviscid fluid through two dimensional planar cascades of airfoils was derived, together with its appropriate boundary conditions. A computer program, CAS2D, was developed that numerically solves an artificially time-dependent form of the actual FPE. The governing equation was discretized by using type-dependent, rotated finite differencing and the finite area technique. The flow field was discretized by providing a boundary-fitted, nonuniform computational mesh. The mesh was generated by using a sequence of conforming mapping, nonorthogonal coordinate stretching, and local, isoparametric, bilinear mapping functions. The discretized form of the FPE was solved iteratively by using successive line overrelaxation. The possible isentropic shocks were correctly captured by adding explicitly an artificial viscosity in a conservative form. In addition, a three-level consecutive, mesh refinement feature makes CAS2D a reliable and fast algorithm for the analysis of transonic, two dimensional cascade flows.
Lattice Boltzmann simulations of 2D laminar flows past two tandem cylinders
NASA Astrophysics Data System (ADS)
Mussa, Alberto; Asinari, Pietro; Luo, Li-Shi
2009-03-01
We apply the lattice Boltzmann equation (LBE) with multiple-relaxation-time (MRT) collision model to simulate laminar flows in two-dimensions (2D). In order to simulate flows in an unbounded domain with the LBE method, we need to address two issues: stretched non-uniform mesh and inflow and outflow boundary conditions. We use the interpolated grid stretching method to address the need of non-uniform mesh. We demonstrate that various inflow and outflow boundary conditions can be easily and consistently realized with the MRT-LBE. The MRT-LBE with non-uniform stretched grids is first validated with a number of test cases: the Poiseuille flow, the flow past a cylinder asymmetrically placed in a channel, and the flow past a cylinder in an unbounded domain. We use the LBE method to simulate the flow past two tandem cylinders in an unbounded domain with Re = 100. Our results agree well with existing ones. Through this work we demonstrate the effectiveness of the MRT-LBE method with grid stretching.
Assessment of the Impacts of Compensation Flow Changes Upon Instream Habitat Using 2D Modelling
NASA Astrophysics Data System (ADS)
Mould, D. C.; Lane, S. N.; Christmas, M.
2004-05-01
Many millstone-grit rivers in northern England are impounded. In such cases the water company in the area has to release compensation flows from the reservoirs, traditionally to meet industrial needs: these flows are rarely set with ecology in mind; and have commonly involved constant flow. Dam overtopping may create spates, but spawning in many fish species is prompted by a spate flow in the early autumn when dams are rarely full enough to overtop. Such flows are important for fine sediment flushing and controlling the wetted useable area for spawning. Classical physical habitat modelling for instream habitat has been largely reliant upon 1D approaches, such as the Instream Flow Incremental Methodology (IFIM). Here we use a 2D finite element model (FESWMS), to simulate changes in instream habitat with variations in the compensation flow regimes. The spatial resolution of 2D models can be adapted to the scale of fish habitats so providing better representation of the reach-scale flow processes (such as slack water in the margins, wetting and drying) than the 1D case. The model is applied to the Rivers Rivelin and Loxley in Sheffield, Northern England. At the confluence of the two rivers, the compensation flow level is set at 30.6 Thousand Cubic Metres per Day (TCMD). Due to historical reasons, the compensation is not divided equally, as the Loxley receives 28 TCMD whilst the Rivelin receives only 2.6 TCMD. The model is used to simulate a transfer of 6 TCMD from the Loxley to the Rivelin. After validation, model predictions are combined with available habitat requirement data (e.g. velocity and depth needs) to develop an index of change in habitat suitability in terms of first order variables (e.g. velocity, depth and wetted useable area). This suggests that the change in compensation may significantly improve instream ecology in relation to macroinvertebrates, brown trout (Salmo trutta) and bullhead (Cottus gobio) in the Rivelin without causing detrimental impacts
Foam flows in 2D porous media: intermittency and bubble fragmentation
NASA Astrophysics Data System (ADS)
Meheust, Y.; Géraud, B.; Jones, S. A.; Dollet, B.; Cantat, I.
2014-12-01
Flowing foams are used in many engineering and technical applications. A well-known application is oil recovery. Another one is the remediation of polluted soils: the foam is injected into the ground in order to mobilize chemical species present in the medium. Apart from potential interesting physico-chemical and biochemical properties, foams have peculiar flow properties that applications might benefit of. In particular, viscous dissipation arises mostly from the contact zones between the soap films and the walls, which results in peculiar friction laws allowing the foam to invade narrow pores more efficiently than Newtonian fluids would. In most experimental studies no local information of the foam structure is possible, and only global quantities such as the effective viscosity can be measured. Using two-dimensional transparent flow cells, we have previously shown that foam structural [1] and elastic [2] effects significantly impact the flow of foams in porous media. We now present an investigation of foam flow through a two-dimensional (2D) porous medium consisting of circular obstacles positioned randomly in a Hele-Shaw cell (see figure). The foam structure is recorded in time by a video camera and subsequently analyzed by image processing, which provides us with the velocity field and spatial distribution of bubble sizes. The flow exhibits a rich phenomenology, including flow irreversibility, preferential flow paths, local flow intermittency/non-stationarity (despite the imposed permanent global flow rate). Moreover, the medium impacts the nature of the flowing fluid by selecting the bubble size through bubble fragmentation. We investigate how preferential flow paths and intermittency depend on the imposed global flow rate and foam quality (the water content), and show that the spatial distribution of bubble sizes is to some extent correlated with the velocity field. We furthermore measure the evolution, along the flow direction, of the probability density
Liquid Flow in Biofilm Systems
Stoodley, Paul; deBeer, Dirk; Lewandowski, Zbigniew
1994-01-01
A model biofilm consisting of Pseudomonas aeruginosa, Pseudomonas fluorescens, and Klebsiella pneumoniae was developed to study the relationships between structural heterogeneity and hydrodynamics. Local fluid velocity in the biofilm system was measured by a noninvasive method of particle image velocimetry, using confocal scanning laser microscopy. Velocity profiles were measured in conduit and porous medium reactors in the presence and absence of biofilm. Liquid flow was observed within biofilm channels; simultaneous imaging of the biofilm allowed the liquid velocity to be related to the physical structure of the biofilm. Images PMID:16349345
An Integrative Model of Excitation Driven Fluid Flow in a 2D Uterine Channel
NASA Astrophysics Data System (ADS)
Maggio, Charles; Fauci, Lisa; Chrispell, John
2009-11-01
We present a model of intra-uterine fluid flow in a sagittal cross-section of the uterus by inducing peristalsis in a 2D channel. This is an integrative multiscale computational model that takes as input fluid viscosity, passive tissue properties of the uterine channel and a prescribed wave of membrane depolarization. This voltage pulse is coupled to a model of calcium dynamics inside a uterine smooth muscle cell, which in turn drives a kinetic model of myosin phosphorylation governing contractile muscle forces. Using the immersed boundary method, these muscle forces are communicated to a fluid domain to simulate the contractions which occur in a human uterus. An analysis of the effects of model parameters on the flow properties and emergent geometry of the peristaltic channel will be presented.
Wavelet diagnostics of the flow control of unsteady separation on a 2D Wind Turbine Airfoil
NASA Astrophysics Data System (ADS)
Bai, Zhe; Lewalle, Jacques; Wang, Guannan; Glauser, Mark
2013-11-01
We investigated the aerodynamic characteristics of a 2D wind turbine airfoil. Unsteadiness was associated with the wake of a cylinder upstream of the airfoil. The experiments were conducted in both the baseline case, and with active closed-loop control on the suction surface of the airfoil. The data consisted of surface pressure time series. Continuous wavelet analysis gave the phase, band-pass filtered signals and envelope of harmonics of the fundamental shedding frequency. Coherence of pairs of signals was also used to map the flow characteristics. For the baseline and controlled case, we will report on the relation between phase of the leading edge fluctuations, unsteady flow separation and lift and drag coefficients. Our goal is to develop a more effective controller. The experiment was funded by DoE through University of Minnesota Wind Energy Consortium. Thanks for the support from the MAE department of Syracuse University.
Quasi-simultaneous interaction method for solving 2D boundary layer flows over plates and airfoils
NASA Astrophysics Data System (ADS)
Bijleveld, H. A.; Veldman, A. E. P.
2012-11-01
This paper studies unsteady 2D boundary layer flows over dented plates and a NACA 0012 airfoil. An inviscid flow is assumed to exist outside the boundary layer and is solved iteratively with the boundary layer flow together with the interaction method until a matching solution is achieved. Hereto a quasi-simultaneous interaction method is applied, in which the integral boundary layer equations are solved together with an interaction-law equation. The interaction-law equation is an approximation of the external flow and based on thin-airfoil theory. It is an algebraic relation between the velocity and displacement thickness. The interaction-law equation ensures that the eigenvalues of the system of equations do not have a sign change and that no singularities occur. Three numerical schemes are used to solve the boundary layer flow with the interaction method. These are: a standard scheme, a splitting method and a characteristics solver. All schemes use a finite difference discretization. The three schemes yield comparable results for the simulations carried out. The standard scheme is deviating most from the splitting and characteristics solvers. The results show that the eigenvalues remain positive, even in separation. As expected, the addition of the interaction-law equation prevents a sign change of the eigenvalues. The quasi-simultaneous interaction scheme is applicable to the three numerical schemes tested.
A 2D pendulum submitted to an incoming flow: drag acting like gravity and new instabilities
NASA Astrophysics Data System (ADS)
Fani, Andrea; Gallaire, Francois
2013-11-01
Flow induced oscillations of slender bodies facing an incoming flow are relevant in a large number of engineering applications, such as the design of tubular structures of offshore platforms, heat exchangers and energy harvesting. Numerical simulations and experiments available in literature often consider a circular cylinder in an uniform flow which can move only transversally with respect to the flow direction. In a recent work Semin et al. (JFM, 2011) studied a tethered 2D cylinder strongly confined between two parallel plane walls. It is shown that confinement alters significantly the flow dynamics, with a new instability, denoted confinement induced vibration (CIV), which occur at a Reynolds number much lower than the vortex induced vibration (VIV) critical one. In the present work we characterize the instability scenario of a confined tethered cylinder by means of a global stability analysis of the fluid-structure problem. In strongly confined channels, a periodic unstable mode, related to CIV vibrations, is observed, while for moderated confinement a new steady diverging instability is founded.
Burylov, S V; Zakhlevnykh, A N
2016-06-01
We study the Freedericksz transition induced by a magnetic field in a rectangular cell filled with a nematic liquid crystal. In the initial state the director of the nematic liquid crystal is uniformly aligned in the cross section plane of the cell with rigid anchoring of the director at cell walls: planar on the top and bottom walls, and homeotropic on the left and right ones. The magnetic field is directed perpendicular to the cell cross section plane. We consider two-dimensional (2D) orientational deformations of the nematic liquid crystal in the rectangular cell and determine the critical value of the Freedericksz transition field above which these orientational deformations occur. The 2D expression for the director alignment profile above the threshold of Freedericksz transition is analytically found and the profile shapes as functions of cell sizes, values of the Frank elastic constants of the nematic liquid crystal and the magnetic field are studied. PMID:27349554
Self-Organization in 2D Traffic Flow Model with Jam-Avoiding Drive
NASA Astrophysics Data System (ADS)
Nagatani, Takashi
1995-04-01
A stochastic cellular automaton (CA) model is presented to investigate the traffic jam by self-organization in the two-dimensional (2D) traffic flow. The CA model is the extended version of the 2D asymmetric exclusion model to take into account jam-avoiding drive. Each site contains either a car moving to the up, a car moving to the right, or is empty. A up car can shift right with probability p ja if it is blocked ahead by other cars. It is shown that the three phases (the low-density phase, the intermediate-density phase and the high-density phase) appear in the traffic flow. The intermediate-density phase is characterized by the right moving of up cars. The jamming transition to the high-density jamming phase occurs with higher density of cars than that without jam-avoiding drive. The jamming transition point p 2c increases with the shifting probability p ja. In the deterministic limit of p ja=1, it is found that a new jamming transition occurs from the low-density synchronized-shifting phase to the high-density moving phase with increasing density of cars. In the synchronized-shifting phase, all up cars do not move to the up but shift to the right by synchronizing with the move of right cars. We show that the jam-avoiding drive has an important effect on the dynamical jamming transition.
NASA Astrophysics Data System (ADS)
Qi, Zhiyuan; Nguyen, Zoom; Park, Cheol; Maclennan, Joe; Maclennan, Matt; Clark, Noel
2012-02-01
The quantization of film thickness in freely suspended fluid smectic liquid crystal film enables the study of the hydrodynamics of drops and interfaces in 2D. We report microfluidic experiments, in which we observe the hydrodynamics of 2D drops flowing in channels. Using high-speed video microscopy, we track the shape of 2D drops and interfaces, visualizing the deterministic lateral displacement-based separation and pinched flow separation phenomena previously observed only in 3D. Finally, we demonstrate techniques for 2D drop generation and sorting, which will be used for 2D microfluidic applications.
Liquid cooled counter flow turbine bucket
Dakin, James T.
1982-09-21
Means and a method are provided whereby liquid coolant flows radially outward through coolant passages in a liquid cooled turbine bucket under the influence of centrifugal force while in contact with countercurrently flowing coolant vapor such that liquid is entrained in the flow of vapor resulting in an increase in the wetted cooling area of the individual passages.
Simulation of abrasive flow machining process for 2D and 3D mixture models
NASA Astrophysics Data System (ADS)
Dash, Rupalika; Maity, Kalipada
2015-12-01
Improvement of surface finish and material removal has been quite a challenge in a finishing operation such as abrasive flow machining (AFM). Factors that affect the surface finish and material removal are media viscosity, extrusion pressure, piston velocity, and particle size in abrasive flow machining process. Performing experiments for all the parameters and accurately obtaining an optimized parameter in a short time are difficult to accomplish because the operation requires a precise finish. Computational fluid dynamics (CFD) simulation was employed to accurately determine optimum parameters. In the current work, a 2D model was designed, and the flow analysis, force calculation, and material removal prediction were performed and compared with the available experimental data. Another 3D model for a swaging die finishing using AFM was simulated at different viscosities of the media to study the effects on the controlling parameters. A CFD simulation was performed by using commercially available ANSYS FLUENT. Two phases were considered for the flow analysis, and multiphase mixture model was taken into account. The fluid was considered to be a
Debris Flow Hazard Map Simulation using FLO-2D For Selected Areas in the Philippines
NASA Astrophysics Data System (ADS)
Khallil Ferrer, Peter; Llanes, Francesca; dela Resma, Marvee; Realino, Victoriano, II; Obrique, Julius; Ortiz, Iris Jill; Aquino, Dakila; Narod Eco, Rodrigo; Mahar Francisco Lagmay, Alfredo
2014-05-01
On December 4, 2012, Super Typhoon Bopha wreaked havoc in the southern region of Mindanao, leaving 1,067 people dead and causing USD 800 million worth of damage. Classified as a Category 5 typhoon by the Joint Typhoon Warning Center (JTWC), Bopha brought intense rainfall and strong winds that triggered landslides and debris flows, particularly in Barangay (village) Andap, New Bataan municipality, in the southern Philippine province of Compostela Valley. The debris flow destroyed school buildings and covered courts and an evacuation center. Compostela Valley also suffered the most casualties of any province: 612 out of a total of 1,067. In light of the disaster in Compostela, measures were immediately devised to improve available geohazard maps to raise public awareness about landslides and debris flows. A debris flow is a very rapid to extremely rapid flow of saturated non-plastic debris in a steep channel. They are generated when heavy rainfall saturates sediments, causing them to flow down river channels within an alluvial fan situated at the base of the slope of a mountain drainage network. Many rural communities in the Philippines, such as Barangay Andap, are situated at the apex of alluvial fans and in the path of potential debris flows. In this study, we conducted simulations of debris flows to assess the risks in inhabited areas throughout the Philippines and validated the results in the field, focusing on the provinces of Pangasinan and Aurora as primary examples. Watersheds that drain in an alluvial fan using a 10-m resolution Synthetic Aperture Radar (SAR)-derived Digital Elevation Model (DEM) was first delineated, and then a 1 in 100-year rain return rainfall scenario for the watershed was used to simulate debris flows using FLO-2D, a flood-routing software. The resulting simulations were used to generate debris flow hazard maps which are consistent with danger zones in alluvial fans delineated previously from satellite imagery and available DEMs. The
NASA Astrophysics Data System (ADS)
Tripathi, Neha; Saha, Satyen
2014-06-01
Room temperature ionic liquids are one of the most exciting classes of materials in the last decade. In particular piperidinium (PIP) cation based ionic liquid (IL) (such as PIP14NTf2) have found application in electrochemistry/batteries. In this Letter, 2D NMR (NOESY and HOESY) is employed for studying the interactions present between cations and anions. HOESY spectrum shows that fluorine of NTf2 unusually interacts with all proton of the cation (PIP14). Combined HOESY and NOESY indicate that NTf2 anion is distributed heterogeneously in liquid. Existence of micro heterogeneity in this important class of IL is proposed.
Liquid Bismuth Propellant Flow Sensor
NASA Technical Reports Server (NTRS)
Polzin, Kurt A.; Stanojev, B. J.; Korman, V.
2007-01-01
Quantifying the propellant mass flow rate in liquid bismuth-fed electric propulsion systems has two challenging facets. First, the flow sensors must be capable of providing a resolvable measurement at propellant mass flow rates on the order of 10 mg/see with and uncertainty of less that 5%. The second challenge has to do with the fact that the materials from which the flow sensors are fabricated must be capable of resisting any of the corrosive effects associated with the high-temperature propellant. The measurement itself is necessary in order to properly assess the performance (thrust efficiency, Isp) of thruster systems in the laboratory environment. The hotspot sensor[I] has been designed to provide the bismuth propellant mass flow rate measurement. In the hotspot sensor, a pulse of thermal energy (derived from a current pulse and associated joule heating) is applied near the inlet of the sensor. The flow is "tagged" with a thermal feature that is convected downstream by the flowing liquid metal. Downstream, a temperature measurement is performed to detect a "ripple" in the local temperature associated with the passing "hotspot" in the propellant. By measuring the time between the upstream generation and downstream detection of the thermal feature, the flow speed can be calculated using a "time of flight" analysis. In addition, the system can be calibrated by measuring the accumulated mass exiting the system as a-function of time and correlating this with the time it takes the hotspot to convect through the sensor. The primary advantage of this technique is that it doesn't depend on an absolute measurement of temperature but, instead, relies on the observation of thermal features. This makes the technique insensitive to other externally generated thermal fluctuations. In this paper, we describe experiments performed using the hotspot flow sensor aimed at quantifying the resolution of the sensor technology. Propellant is expelled onto an electronic scale to
NASA Astrophysics Data System (ADS)
Tucciarelli, T.
2012-12-01
A new methodology for the solution of irrotational 2D flow problems in domains with strongly unstructured meshes is presented. A fractional time step procedure is applied to the original governing equations, solving consecutively a convective prediction system and a diffusive corrective system. The non linear components of the problem are concentrated in the prediction step, while the correction step leads to the solution of a linear system, of the order of the number of computational cells. A MArching in Space and Time (MAST) approach is applied for the solution of the convective prediction step. The major advantages of the model, as well as its ability to maintain the solution monotonicity even in strongly irregular meshes, are briefly described. The algorithm is applied to the solution of diffusive shallow water equations in a simple domain.
An Experimental Study of Flow Separation over 2D Transverse Grooves
NASA Astrophysics Data System (ADS)
Jones, Emily; Lang, Amy; Afroz, Farhana; Wheelus, Jennifer; Smith, Drew
2011-11-01
A shark's scales help to reduce drag over its body by controlling boundary layer separation over its skin. It is theorized that the scales bristle when encountering a reversing flow, thereby trapping vortices between the scales, creating a partial slip condition over the surface and inducing turbulence augmentation in the boundary layer. In an attempt to replicate and study these effects, a spinning cylinder was used in a water tunnel to induce separation over a flat plate with 2 millimeter square 2D transverse grooves. The results were compared to separation occurring over a flat plate without grooves using DPIV. The angular speed of the cylinder was varied. The observed delays in separation, changes in separation bubble shedding frequency and other effects upon the boundary layer are discussed.
A case study of fluid flow in fractured rock mass based on 2-D DFN modeling
NASA Astrophysics Data System (ADS)
Han, Jisu; Noh, Young-Hwan; Um, Jeong-Gi; Choi, Yosoon
2014-05-01
A two dimensional steady-state fluid flow through fractured rock mass of an abandoned copper mine in Korea is addressed based on discrete fracture network modeling. An injection well and three observation wells were installed at the field site to monitor the variations of total heads induced by injection of fresh water. A series of packer tests were performed to estimate the rock mass permeability. First, the two dimensional stochastic fracture network model was built and validated for a granitic rock mass using the geometrical and statistical data obtained from surface exposures and borehole logs. This validated fracture network model was combined with the fracture data observed on boreholes to generate a stochastic-deterministic fracture network system. Estimated apertures for each of the fracture sets using permeability data obtained from borehole packer tests were discussed next. Finally, a systematic procedure for fluid flow modeling in fractured rock mass in two dimensional domain was presented to estimate the conductance, flow quantity and nodal head in 2-D conceptual linear pipe channel network. The results obtained in this study clearly show that fracture geometry parameters (orientation, density and size) play an important role in the hydraulic behavior of fractured rock masses.
Flow-induced protein crystallization: Macroscopic effects on 2D crystals
NASA Astrophysics Data System (ADS)
Young, James; Posada, David; Hirsa, Amir; Lopez, Juan
2012-11-01
Proteins must first be crystallized before their molecular structure can be studied in detail. However, crystallizing protein is a challenging task which is often met with limited success. Although 2-D protein crystals at the air/water interface are usually obtained under quiescent conditions, it was recently shown that crystallization can be enhanced by a shearing flow. Here we examine the relationship between Reynolds number and the crystal growth process using the deep-channel surface viscometer geometry. It consists of an annular region bounded by stationary inner and outer cylinders and driven by a constant rotation of the floor. The interfacial velocity measurements are compared to Navier-Stokes computations with the Boussinesq-Scriven surface model. The interfacial film is lifted onto a solid substrate, and the protein crystals are observed via optical and atomic force microscopy. For a particular protein surface concentration, a Reynolds number threshold has been identified for flow-induced crystallization. This flow geometry also allows for the determination of the surface shear viscosity, which provides a quantitative measure of the mesoscale interactions associated with protein crystallization.
Micro PIV measurements of turbulent flow over 2D structured roughness
NASA Astrophysics Data System (ADS)
Hartenberger, Joel; Perlin, Marc
2015-11-01
We investigate the turbulent boundary layer over surfaces with 2D spanwise square and triangular protrusions having nominal heights of 100 - 300 microns for Reynolds numbers ranging from Reτ ~ 1500 through Reτ ~ 4500 using a high speed, high magnification imaging system. Micro PIV analysis gives finely resolved velocity fields of the flow (on the order of 10 microns between vectors) enabling a detailed look at the inner region as well as the flow in the immediate vicinity of the roughness elements. Additionally, planar PIV with lower resolution is performed to capture the remainder of the boundary layer to the freestream flow. Varying the streamwise distance between individual roughness elements from one to ten times the nominal heights allows investigation of k-type and d-type roughness in both the transitionally rough and fully rough regimes. Preliminary results show a shift in the mean velocity profile similar to the results of previous studies. Turbulent statistics will be presented also. The authors would like to acknowledge the support of NAVSEA which funded this project through the Naval Engineering Education Center (NEEC).
Liquid metal Flow Meter - Final Report
Andersen, C.; Hoogendoom, S.; Hudson, B.; Prince, J.; Teichert, K.; Wood, J.; Chase, K.
2007-01-30
Measuring the flow of liquid metal presents serious challenges. Current commercially-available flow meters use ultrasonic, electromagnetic, and other technologies to measure flow, but are inadequate for liquid metal flow measurement because of the high temperatures required by most liquid metals. As a result of the reactivity and high temperatures of most liquid metals, corrosion and leakage become very serious safety concerns. The purpose of this project is to develop a flow meter for Lockheed Martin that measures the flow rate of molten metal in a conduit.
Numerical solution of 2D wet steam flow with non-equilibrium condensation and real thermodynamics
Hric, V.; Halama, J.
2015-03-10
An approach to modeling of wet steam flow with non-equilibrium condensation phenomenon is presented. The first part of our flow model is homogeneous Euler system of transport equations for mass, momentum and total energy of wet steam (mixture). The additional second part describes liquid phase via non-homogeneous system of transport equations for moments of droplets number distribution function and relies on corrected classical nucleation theory. Moment equations are closed by linearization of droplet growth rate model. All necessary relations for thermodynamic properties of steam are provided by IAPWS set of equations. However, properties of condensate are simply modeled by liquid saturation data. Two real equations of state are implemented. Recently developed CFD formulation for entropy (does not require iteration process) and so-called IAPWS special gas equation for Helmholtz energy (one iteration loop is necessary). Flow model is validated on converging-diverging supersonic nozzle with Barschdorff geometry. Simulations were performed by in-house CFD code based on finite volume method and stiff character of equations was solved by symmetrical time operator splitting. Achieved results satisfactorily agreed with experimental data.
Thermochemical Nonequilibrium 2D Modeling of Nitrogen Inductively Coupled Plasma Flow
NASA Astrophysics Data System (ADS)
Yu, Minghao; Yusuke, Takahashi; Hisashi, Kihara; Ken-ichi, Abe; Kazuhiko, Yamada; Takashi, Abe; Satoshi, Miyatani
2015-09-01
Two-dimensional (2D) numerical simulations of thermochemical nonequilibrium inductively coupled plasma (ICP) flows inside a 10-kW inductively coupled plasma wind tunnel (ICPWT) were carried out with nitrogen as the working gas. Compressible axisymmetric Navier-Stokes (N-S) equations coupled with magnetic vector potential equations were solved. A four-temperature model including an improved electron-vibration relaxation time was used to model the internal energy exchange between electron and heavy particles. The third-order accuracy electron transport properties (3rd AETP) were applied to the simulations. A hybrid chemical kinetic model was adopted to model the chemical nonequilibrium process. The flow characteristics such as thermal nonequilibrium, inductive discharge, effects of Lorentz force were made clear through the present study. It was clarified that the thermal nonequilibrium model played an important role in properly predicting the temperature field. The prediction accuracy can be improved by applying the 3rd AETP to the simulation for this ICPWT. supported by Grant-in-Aid for Scientific Research (No. 23560954), sponsored by the Japan Society for the Promotion of Science
Hydrodynamics of embedded planets' first atmospheres - I. A centrifugal growth barrier for 2D flows
NASA Astrophysics Data System (ADS)
Ormel, Chris W.; Kuiper, Rolf; Shi, Ji-Ming
2015-01-01
In the core accretion paradigm of planet formation, gas giants only form a massive atmosphere after their progenitors exceeded a threshold mass: the critical core mass. Most (exo)planets, being smaller and rock/ice-dominated, never crossed this line. Nevertheless, they were massive enough to attract substantial amounts of gas from the disc, while their atmospheres remained in pressure-equilibrium with the disc. Our goal is to characterize the hydrodynamical properties of the atmospheres of such embedded planets and the implications for their (long-term) evolution. In this paper - the first in series - we start to investigate the properties of an isothermal and inviscid flow past a small, embedded planet by conducting local, 2D hydrodynamical simulations. Using the PLUTO code, we confirm that the flow is steady and bound. This steady outcome is most apparent for the log-polar grid (with the grid spacing proportional to the distance from the planet). For low-mass planets, Cartesian grids are somewhat less efficient as they have difficulty to follow the circular, large speeds in the deep atmosphere. Relating the amount of rotation to the gas fraction of the atmosphere, we find that more massive atmospheres rotate faster - a finding consistent with Kelvin's circulation theorem. Rotation therefore limits the amount of gas that planets can acquire from the nebula. Dependent on the Toomre-Q parameter of the circumstellar disc, the planet's atmosphere will reach Keplerian rotation before self-gravity starts to become important.
Accurate Angle Estimator for High-Frame-Rate 2-D Vector Flow Imaging.
Villagomez Hoyos, Carlos Armando; Stuart, Matthias Bo; Hansen, Kristoffer Lindskov; Nielsen, Michael Bachmann; Jensen, Jorgen Arendt
2016-06-01
This paper presents a novel approach for estimating 2-D flow angles using a high-frame-rate ultrasound method. The angle estimator features high accuracy and low standard deviation (SD) over the full 360° range. The method is validated on Field II simulations and phantom measurements using the experimental ultrasound scanner SARUS and a flow rig before being tested in vivo. An 8-MHz linear array transducer is used with defocused beam emissions. In the simulations of a spinning disk phantom, a 360° uniform behavior on the angle estimation is observed with a median angle bias of 1.01° and a median angle SD of 1.8°. Similar results are obtained on a straight vessel for both simulations and measurements, where the obtained angle biases are below 1.5° with SDs around 1°. Estimated velocity magnitudes are also kept under 10% bias and 5% relative SD in both simulations and measurements. An in vivo measurement is performed on a carotid bifurcation of a healthy individual. A 3-s acquisition during three heart cycles is captured. A consistent and repetitive vortex is observed in the carotid bulb during systoles. PMID:27093598
Turbulence modeling for subsonic separated flows over 2-D airfoils and 3-D wings
NASA Astrophysics Data System (ADS)
Rosen, Aaron M.
Accurate predictions of turbulent boundary layers and flow separation through computational fluid dynamics (CFD) are becoming more and more essential for the prediction of loads in the design of aerodynamic flight components. Standard eddy viscosity models used in many commercial codes today do not capture the nonequilibrium effects seen in a separated flow and thus do not generally make accurate separation predictions. Part of the reason for this is that under nonequilibrium conditions such as a strong adverse pressure gradient, the history effects of the flow play an important role in the growth and decay of turbulence. More recent turbulence models such as Olsen and Coakley's Lag model and Lillard's lagRST model seek to simulate these effects by lagging the turbulent variables when nonequilibrium effects become important. The purpose of the current research is to assess how these nonequilibrium turbulence models capture the separated regions on various 2-D airfoils and 3-D wings. Nonequilibrium models including the Lag model and the lagRST model are evaluated in comparison with three baseline models (Spalart-Allmaras, Wilcox's k-omega, and Menter's SST) using a modified version of the OVERFLOW code. Tuning the model coefficients of the Lag and lagRST models is also explored. Results show that the various lagRST formulations display an improvement in velocity profile predictions over the standard RANS models, but have trouble capturing the edge of the boundary layer. Experimental separation location measurements were not available, but several trends are noted which may be useful to tuning the model coefficients in the future.
Heat Flow Partitioning Between Continents and Oceans - from 2D to 3D
NASA Astrophysics Data System (ADS)
Moresi, L. N.; Cooper, C. M.; Lenardic, A.
2010-12-01
Scalings derived from thermal network theory explain how the presence of continents can influence the Earth’s overall heat loss. Intuitively, it may seem that increasing the proportion of a planet’s surface area covered by continents would decrease the efficiency of heat transfer given that continents do not participate in convective overturn. However, this ignores the potential feedback between the insulating effect of continents and the temperature-dependent viscosity of the mantle (Lenardic et al, 2005, Cooper et al, 2007). When this feedback is considered, a clear regime exists in which the partial stagnation and insulation of the surface by buoyant continental crust can lead to an increase in heat flow compared to the uninsulated case. The numerical results used to verify the scalings have mostly been conducted in two dimensions in order to cover a very wide range of Rayleigh number, fraction of continental coverage, and continental thickness. However as more recent results show that the configuration of the crust also plays a role in determining the heat flow partitioning and global heat flow (See Lenardic et al, “Continents, Super-Continents, Mantle Thermal Mixing, and Mantle Thermal Isolation” in this session), we have begun to repeat this exhaustive and exhausting 2D study in 3D. Cooper, C.M., A. Lenardic, and L.-N. Moresi "Effects of continental insulation and the partioning of heat producing elements on the Earth's heat loss." Geophys. Res. Lett., 33 ,10.1029, 2006. Lenardic, A., L.-N. Moresi, A.M. Jellinek, and M. Manga "Continental insulation, mantle cooling, and the surface area of oceans and continents." Earth Planet. Sci. Lett., 234 ,317-333, 2005.
NASA Astrophysics Data System (ADS)
García-Salaberri, P. A.; Vera, M.
2015-07-01
The influence of assembly compression on the performance of liquid-feed DMFCs under methanol-limiting conditions is explored by means of a 2D/1D multiphysics across-the-channel model. The numerical formulation incorporates a comprehensive 2D description of the anode GDL, including two-phase phenomena, non-uniform anisotropic transport properties, and electrical contact resistances at the GDL/BPP interface. GDL effective properties are evaluated using empirical data corresponding to Toray® carbon paper. A simplified but physically sound 1D description, locally coupled to the 2D anode GDL model, is adopted to describe transport processes in the MPLs, membrane and cathode GDL, whereas the catalyst layers are treated as infinitely thin surfaces. Good agreement is found between the numerical results and previous experimental data. The interplay between assembly compression, bipolar plate material, and channel configuration is also investigated. The results show that there is an optimum GDL compression ratio in terms of overall power density, the optimal compression level being strongly dependent on bipolar plate material. Beyond the optimum, the detrimental effect of compression is larger in non-parallel flow fields due to the additional reduction of methanol transported by under-rib convection. The results suggest that, under certain conditions, this transport mechanism could be more important than diffusion in the anode of liquid-feed DMFCs.
Gabbour, Maya; Schnell, Susanne; Jarvis, Kelly; Robinson, Joshua D.; Markl, Michael
2015-01-01
Background Doppler echocardiography (echo) is the reference standard for blood flow velocity analysis, and two-dimensional (2-D) phase-contrast magnetic resonance imaging (MRI) is considered the reference standard for quantitative blood flow assessment. However, both clinical standard-of-care techniques are limited by 2-D acquisitions and single-direction velocity encoding and may make them inadequate to assess the complex three-dimensional hemodynamics seen in congenital heart disease. Four-dimensional flow MRI (4-D flow) enables qualitative and quantitative analysis of complex blood flow in the heart and great arteries. Objectives The objectives of this study are to compare 4-D flow with 2-D phase-contrast MRI for quantification of aortic and pulmonary flow and to evaluate the advantage of 4-D flow-based volumetric flow analysis compared to 2-D phase-contrast MRI and echo for peak velocity assessment in children and young adults. Materials and methods Two-dimensional phase-contrast MRI of the aortic root, main pulmonary artery (MPA), and right and left pulmonary arteries (RPA, LPA) and 4-D flow with volumetric coverage of the aorta and pulmonary arteries were performed in 50 patients (mean age: 13.1±6.4 years). Four-dimensional flow analyses included calculation of net flow and regurgitant fraction with 4-D flow analysis planes similarly positioned to 2-D planes. In addition, 4-D flow volumetric assessment of aortic root/ascending aorta and MPA peak velocities was performed and compared to 2-D phase-contrast MRI and echo. Results Excellent correlation and agreement were found between 2-D phase-contrast MRI and 4-D flow for net flow (r=0.97, P<0.001) and excellent correlation with good agreement was found for regurgitant fraction (r= 0.88, P<0.001) in all vessels. Two-dimensional phase-contrast MRI significantly underestimated aortic (P= 0.032) and MPA (P<0.001) peak velocities compared to echo, while volumetric 4-D flow analysis resulted in higher (aortic: P=0
Full 2D observation of water surface elevation from SWOT under different flow conditions
NASA Astrophysics Data System (ADS)
Domeneghetti, Alessio; Schumann, Guy; Rui, Wei; Durand, Michael; Pavelsky, Tamlin
2016-04-01
The upcoming Surface Water and Ocean Topography (SWOT) satellite mission is a joint project of NASA, Centre National d'Etudes Spatiales (CNES, France), the Canadian Space Agency, and the Space Agency of the UK that will provide a first global, high-resolution observation of ocean and terrestrial water surface heights. Characterized by an observation swath of 120 km and an orbit repeat interval of about 21 days, SWOT will provide unprecedented bi-dimensional observations of rivers wider than 50-100 m. Despite many research activities that have investigated potential uses of remotely sensed data from SWOT, potentials and limitations of the spatial observations provided by the satellite mission for flood modeling still remain poorly understood and investigated. In this study we present a first analysis of the spatial observation of water surface elevation that is expected from SWOT for a 140 km reach of the middle-lower portion of the Po River, in Northern Italy. The river stretch is characterized by a main channel varying from 200-500 m in width and a floodplain that can be as wide as 5 km and that is delimited by a system of major embankments. The reconstruction of the hydraulic behavior of the Po River is performed by means of a quasi-2d model built with detailed topographic and bathymetric information (LiDAR, 2 m resolution), while the simulation of the spatial observation sensed by SWOT is performed with a SWOT simulator that mimics the satellite sensor characteristics. Referring to water surface elevations associated with different flow conditions (maximum, minimum and average flow reproduced by means of the quasi-2d numerical model) this work provides a first characterization of the spatial observations provided by SWOT and highlights the strengths and limitations of the expected products. By referring to a real river reach the analysis provides a credible example of the type of spatial observations that will be available after launch of SWOT and offers a first
Titan2D Based Pyroclastic Flows Hazard Maps for Santa Ana Volcano, El Salvador
NASA Astrophysics Data System (ADS)
Bajo, J. V.; Martinez-Hackert, B.; Escobar, C. D.; Gutierrez, R. E.
2009-05-01
Santa Ana Volcano is located in the Apaneca Volcanic Field located to the west of El Salvador, Central America. It is one the six active volcanoes monitor by the Servicios Nacionales de Estudios Territoriales (SNET) in El Salvador, out of twenty that are considered active in this small country by Smithsonian definition. The Santa Ana Volcano is surrounded by rural communities in its proximal areas and in its close distal areas by the second largest city of the country. On October 1st 2005, after a few months of increased fumarolic and seismic activity, it erupted generating a 10 km high steam and ash plume, reportedly seen by some aircraft and estimated using photography by SNET members. Ash was deposited to the west, north-west part of the country, following typical wind pattern for the region, as well as small pyroclastic flows and major lahars in its eastern part. Coffee plantations were lost, as was some crop of coffee in the following season. However, to the west the ash fertilized the land and resulted in an enhanced harvest of coffee beans. Only 2 people were killed from the Blast, thanks to the auto evacuation of proximal communities. Whilst the last eruption had a relatively low human life toll, a stronger eruption spells havoc almost certainly for the region. At this moment no exhaustive study and understanding exists of the pyroclastic flows generated by the Santa Ana Volcano nor a map for this particular hazard. This study proposes the use of Titan2D for those two purposes, using a DEM generated by the SNET using topographic maps as well as DEMs generated using Advanced Spaceborne Thermal Emission and Reflection Radiometer Images (ASTER).
Advances in gas-liquid flows 1990
Kim, J.M. . Nuclear Reactor Lab.); Rohatgi, U.S. ); Hashemi, A. )
1990-01-01
Gas-liquid two-phase flows commonly occur in nature and industrial applications. Rain, clouds, geysers, and waterfalls are examples of natural gas-liquid flow phenomena, whereas industrial applications can be found in nuclear reactors, steam generators, boilers, condensers, evaporators, fuel atomization, heat pipes, electronic equipment cooling, petroleum engineering, chemical process engineering, and many others. The household-variety phenomena such as garden sprinklers, shower, whirlpool bath, dripping faucet, boiling tea pot, and bubbling beer provide daily experience of gas-liquid flows. The papers presented in this volume reflect the variety and richness of gas-liquid two-phase flow and the increasing role it plays in modern technology. This volume contains papers dealing with some recent development in gas-liquid flow science and technology, covering basic gas-liquid flows, measurements and instrumentation, cavitation and flashing flows, countercurrent flow and flooding, flow in various components and geometries liquid metals and thermocapillary effects, heat transfer, nonlinear phenomena, instability, and other special and general topics related to gas-liquid flows.
NASA Astrophysics Data System (ADS)
Baroni, Pierre-Yves; Paeder, Vincent; Chang, Yu-Chi; Roussey, Matthieu; Herzig, Hans Peter; Nakagawa, Wataru
2011-01-01
Superprism-based deflection of an optical beam is observed in a photonic crystal composed of a triangular lattice of pillars infiltrated with a liquid crystal. The device is based on a Silicon-on-insulator substrate and operates in the telecommunications band. The experimental results show a wavelength shift of 0.76 μm/nm, in reasonable agreement with simulations. Temperature-based control of the liquid crystal properties is also shown to modulate the superprism characteristics.
Behaviour of a rimmed elliptical inclusion in 2D slow incompressible viscous flow
NASA Astrophysics Data System (ADS)
Mancktelow, N. S.
2012-04-01
The shape preferred orientation of natural populations of inclusions (or "porphyroclasts") is often inconsistent with predictions from established analytical theory for inclusions with coherent boundaries (e.g., Pennacchioni et al. 2001). A totally incoherent or slipping interface can explain observed stable back-rotated (or antithetic) orientations but not the observed cut-off axial ratio, below which inclusions still rotate. However, this behaviour is reproduced by a rimmed inclusion with a rim viscosity that is not infinitely weak but still weaker than the matrix (e.g., Schmid and Podladchikov 2005; Johnson et al. 2009). In this study, finite-element numerical modelling (FEM) is employed to investigate this system in 2D over a very wide parameter space, from a viscosity ratio (relative to the matrix) of the inclusion from 106 to 1, the rim from 10-6 to 1, the axial ratio from 1.00025 to 20, and the rim thickness from 5% to 20%. Theoretical consideration of a concentric elliptical inclusion and ellipse reduces the number of scalar values to be determined to fully characterize the system to two: one for the rate of stretch of the inclusion and one for the rate of rotation. From these two values, the rotation and stretching rate can be calculated for any orientation and 2D background flow field. For effectively rigid particles, the cut-off axial ratio between rotation and stabilization is determined by the remaining two parameters, namely the rim viscosity and the thickness, with low rim viscosity or thick rims promoting stabilization. The shape fabric of a population of particles in a high strain shear zone, presented as a typical Rf/φ plot, can be forward modelled using an initial value Ordinary Differential Equation (ODE) approach. Because the rim does not remain elliptical to high strain, this method cannot accurately model the behaviour of individual inclusions. However, a statistical approach, allowing variation in rim viscosity, which is also a proxy for
Approaches to Modeling Coupled Flow and Reaction in a 2-D Cementation Experiment
Steefel, Carl; Cochepin, B.; Trotignon, L.; Bildstein, O.; Steefel, C.; Lagneau, V.; van der Lee, J.
2008-04-01
Porosity evolution at reactive interfaces is a key process that governs the evolution and performances of many engineered systems that have important applications in earth and environmental sciences. This is the case, for example, at the interface between cement structures and clays in deep geological nuclear waste disposals. Although in a different transport regime, similar questions arise for permeable reactive barriers used for biogeochemical remediation in surface environments. The COMEDIE project aims at investigating the coupling between transport, hydrodynamics and chemistry when significant variations of porosity occur. The present work focuses on a numerical benchmark used as a design exercise for the future COMEDIE-2D experiment. The use of reactive transport simulation tools like Hytec and Crunch provides predictions of the physico-chemical evolutions that are expected during the future experiments in laboratory. Focus is given in this paper on the evolution during the simulated experiment of precipitate, permeability and porosity fields. A first case is considered in which the porosity is constant. Results obtained with Crunch and Hytec are in relatively good agreement. Differences are attributable to the models of reactive surface area taken into account for dissolution/precipitation processes. Crunch and Hytec simulations taking into account porosity variations are then presented and compared. Results given by the two codes are in qualitative agreement, with differences attributable in part to the models of reactive surface area for dissolution/precipitation processes. As a consequence, the localization of secondary precipitates predicted by Crunch leads to lower local porosities than for predictions obtained by Hytec and thus to a stronger coupling between flow and chemistry. This benchmark highlights the importance of the surface area model employed to describe systems in which strong porosity variations occur as a result of dissolution
Numerical Simulations of the Propagation of a Liquid Plug through a 2D Airway Bifurcation
NASA Astrophysics Data System (ADS)
Vaughan, Benjamin L., Jr.; Grotberg, James B.
2010-11-01
Numerous medical therapies require the instillation of liquids plugs and their delivery throughout the pulmonary airways. This process and the effect on the resulting liquid distribution is controlled by a number of parameters, including airway orientation with respect to gravity, initial plug volume, liquid physical properties, and the imposed airflow rate which drives the plug from behind. The airflow rate defines an operative Capillary number, Ca, and the influence of gravity appears as an effective Bond number, Bo, whose magnitude varies with orientation. In this study, we develop a numerical method for solving the propagation of a liquid plug into a two-dimensional airway bifurcation consisting of a parent channel branching into two daughter channels. We measure the splitting ratio, RS, which is defined as the ratio of the liquid plug volumes between the daughter branches. RS increases with Ca and asymptotes to 1 as Ca goes to infinity, which corresponds to an equal split, while increasing Bo requires a higher value of Ca for an equal split. We also examine the normal and shear stresses on the bifurcation walls and observe that the stresses on the upper walls increase as Bo increases while the stresses on the lower walls decrease as Bo increases.
The propagation of a surfactant laden liquid plug in a 2D-channel
NASA Astrophysics Data System (ADS)
Fujioka, Hideki; Grotberg, James B.
2003-11-01
Liquid is instilled into the pulmonary airways in medical treatments such as surfactant replacement therapy, partial liquid ventilation, and drug delivery. We study numerically the steady finite Re propagation of a surfactant laden liquid plug within a two-dimensional channel lined by a uniform, thin liquid film. For a fixed plug length, the trailing film thickness increases with plug propagation speed. When the plug length is less than the channel width, the trailing film thickness decreases with the plug length. Without surfactant a single pair of recirculation is seen in the plug. When surfactant is present, a second pair of recirculation appears near the front meniscus at finite Re. With increasing Re, the capillary wave at the front meniscus becomes larger causing the wall shear stress and pressure to have sharp peak where the liquid film thickness is smallest. These stresses increase with Re and may induce pulmonary epithelial cell response or damage. This work is supported by NIH grant HL41126, NASA grant NAG3-2740.
Analysis of tunable bandgaps in liquid crystal-infiltrated 2D silicon photonic crystals
NASA Astrophysics Data System (ADS)
Cos, J.; Ferré-Borrull, J.; Pallarès, J.; Marsal, L. F.
2010-09-01
We present a theoretical study on two-dimensional photonic crystals composed of silicon and the E7 liquid crystal. We analyze how the optical axis orientation of the liquid crystal influences the photonic bands and bandgaps, for the case when the Maxwell equations can be decoupled into the TE and TM modes. We consider two different structures, a triangular lattice of E7 liquid crystal cylinders in a silicon background and a triangular lattice of silicon cylinders in an E7 liquid crystal background. The effect of the liquid crystal anisotropy on the geometry of the irreducible Brillouin zone allows us to propose a simplified way to calculate the photonic bandgaps. Results show that the bandgap width and center frequency have a 60° periodicity for both structures. Using the plane-wave expansion method, we determined the maximum bandgap and the optimal radius of the cylinders for each structure. Finally, for the second structure, we propose an optical switch with a 50% duty cycle. These structures can be applied to design tunable photonic devices.
SIMULATIONS OF 2D AND 3D THERMOCAPILLARY FLOWS BY A LEAST-SQUARES FINITE ELEMENT METHOD. (R825200)
Numerical results for time-dependent 2D and 3D thermocapillary flows are presented in this work. The numerical algorithm is based on the Crank-Nicolson scheme for time integration, Newton's method for linearization, and a least-squares finite element method, together with a matri...
Liquid-Flow Controller Responds To Pressure
NASA Technical Reports Server (NTRS)
Cox, George B., Jr.
1990-01-01
Mechanism controls flow of liquid in fuel-spraying head in combustion chamber responds nonlinearly to pressure of liquid. Shell of spraybar expands or contracts laterally as its internal pressure rises or falls, forcing collar down or up on entry tube. Area of window formed by slots in collar and entry tube thus increases or decreases. Drop in pressure through variable-area orifice increases much more with flow through orifice than does corresponding drop in pressure with flow through fixed-area orifice. In practical terms, lower pump pressure needed with variable orifice for given flow of liquid. Principle of operation applicable to spraying heads for other fluids.
A 2-D Pore-Network Model of the Drying of Single-Component Liquids in Porous Media
Yortsos, Yanic C.; Yiotis, A.G.; Stubos, A.K.; Boundovis, A.G.
2000-01-20
The drying of liquid-saturated porous media is typically approaching using macroscopic continuum models involving phenomenological coefficients. Insight on these coefficients can be obtained by a more fundamental study at the pore- and pore-network levels. In this report, a model based on pore-network representation of porous media that accounts for various process at the pore-scale is presented. These include mass transfer by advection and diffusion in the gas phase, viscous flow in liquid and gas phases and capillary effects at the gas-liquid menisci in the pore throats.
Deviations from Fermi-Liquid Behavior above Tc in 2D Short Coherence Length Superconductors
NASA Astrophysics Data System (ADS)
Trivedi, Nandini; Randeria, Mohit
1995-07-01
We show that there are qualitative differences between the temperature dependence of the spin and charge correlations in the normal state of the 2D attractive Hubbard model using quantum Monte Carlo simulations. The one-particle density of states shows a pseudogap above Tc with a depleted N0 with decreasing T. The susceptibility χs and the low frequency spin spectral weight track N0, which explains the spin-gap scaling: 1/T1T~χsT. However, collective excitations contribute to the charge channel, and the compressibility dn/dμ is T independent. This anomalous ``spin-charge separation'' is shown to exist even at intermediate \\|U\\| where the momentum distribution nk gives evidence for a degenerate Fermi system.
Numerical Simulations of High-Frequency Respiratory Flows in 2D and 3D Lung Bifurcation Models
NASA Astrophysics Data System (ADS)
Chen, Zixi; Parameswaran, Shamini; Hu, Yingying; He, Zhaoming; Raj, Rishi; Parameswaran, Siva
2014-07-01
To better understand the human pulmonary system and optimize the high-frequency oscillatory ventilation (HFOV) design, numerical simulations were conducted under normal breathing frequency and HFOV condition using a CFD code Ansys Fluent and its user-defined C programs. 2D and 3D double bifurcating lung models were created, and the geometry corresponds to fifth to seventh generations of airways with the dimensions based on the Weibel's pulmonary model. Computations were carried out for different Reynolds numbers (Re = 400 and 1000) and Womersley numbers (α = 4 and 16) to study the air flow fields, gas transportation, and wall shear stresses in the lung airways. Flow structure was compared with experimental results. Both 2D and 3D numerical models successfully reproduced many results observed in the experiment. The oxygen concentration distribution in the lung model was investigated to analyze the influence of flow oscillation on gas transport inside the lung model.
NASA Astrophysics Data System (ADS)
Stahr, Donald W.; Law, Richard D.
2014-11-01
We model the development of shape preferred orientation (SPO) of a large population of two- and three-dimensional (2D and 3D) rigid clasts suspended in a linear viscous matrix deformed by superposed steady and continuously non-steady plane strain flows to investigate the sensitivity of clasts to changing boundary conditions during a single or superposed deformation events. Resultant clast SPOs are compared to one developed by an identical initial population that experienced a steady flow history of constant kinematic vorticity and reached an identical finite strain state, allowing examination of SPO sensitivity to deformation path. Rotation paths of individual triaxial inclusions are complex, even for steady plane strain flow histories. It has been suggested that the 3D nature of the system renders predictions based on 2D models inadequate for applied clast-based kinematic vorticity gauges. We demonstrate that for a large population of clasts, simplification to a 2D model does provide a good approximation to the SPO predicted by full 3D analysis for steady and non-steady plane strain deformation paths. Predictions of shape fabric development from 2D models are not only qualitatively similar to the more complex 3D analysis, but they display the same limitations of techniques based on clast SPO commonly used as a quantitative kinematic vorticity gauge. Our model results from steady, superposed, and non-steady flow histories with a significant pure shearing component at a wide range of finite strain resemble predictions for an identical initial population that experienced a single steady simple shearing deformation. We conclude that individual 2D and 3D clasts respond instantaneously to changes in boundary conditions, however, in aggregate, the SPO of a population of rigid inclusions does not reflect the late-stage kinematics of deformation, nor is it an indicator of the unique 'mean' kinematic vorticity experienced by a deformed rock volume.
NASA Astrophysics Data System (ADS)
Coelho, João; Mendoza-Sánchez, Beatriz; Pettersson, Henrik; Pokle, Anuj; McGuire, Eva K.; Long, Edmund; McKeon, Lorcan; Bell, Alan P.; Nicolosi, Valeria
2015-06-01
Manganese oxide nanosheets were synthesized using liquid-phase exfoliation that achieved suspensions in isopropanol (IPA) with concentrations of up to 0.45 mg ml-1. A study of solubility parameters showed that the exfoliation was optimum in N,N-dimethylformamide followed by IPA and diethylene glycol. IPA was the solvent of choice due to its environmentally friendly nature and ease of use for further processing. For the first time, a hybrid of graphene and manganese oxide nanosheets was synthesized using a single-step co-exfoliation process. The two-dimensional (2D) hybrid was synthesized in IPA suspensions with concentrations of up to 0.5 mg ml-1 and demonstrated stability against re-aggregation for up to six months. The co-exfoliation was found to be a energetically favorable process in which both solutes, graphene and manganese oxide nanosheets, exfoliate with an improved yield as compared to the single-solute exfoliation procedure. This work demonstrates the remarkable versatility of liquid-phase exfoliation with respect to the synthesis of hybrids with tailored properties, and it provides proof-of-concept ground work for further future investigation and exploitation of hybrids made of two or more 2D nanomaterials that have key complementary properties for various technological applications.
Corrections to Fermi Liquid theory in 2D in a magnetic field
NASA Astrophysics Data System (ADS)
Chubukov, Andrey; Betouras, Joseph; Efremov, Dmitri
2005-03-01
In this work, we consider a Fermi liquid in two dimensions in a magnetic field, and study the effects of the Zeeman splitting on thermodynamics. We derive the temperature dependence of the spin susceptibility χs(T) from the thermodynamic potential, and show explicitly how 2pF scattering gives rise to a non- analytic temperature dependence of the susceptibility. We explain why small momentum scattering does not give rise to non-analytic χs(T). We discuss experimental implications of this result.
Electromagnetic flow rate meter. [for liquid metals
NASA Technical Reports Server (NTRS)
Banks, B. A. (Inventor)
1974-01-01
A liquid metal, whose flow rate is to be determined, is directed through a chamber made of electrically-insulating material on which there is impressed a magnetic field perpendicular to the direction of flow of the liquid metal. The magnetic field is made to increase in strength in a downstream direction of the flow of liquid metal. At least a pair of electrodes are disposed in the chamber traversely and perpendicular to the direction of flow and an ammeter is connected between the electrodes. Electrodes may be disposed in the top or the bottom of the chamber and each may be segmented. Oppositely disposed electrodes may be used with at least one dividing wall extending from each electrode to cause reversal of the direction of flow of the liquid metal. The magnetic field may be provided by electromagnets or permanent magnets such as shaded pole permanent magnets.
NASA Astrophysics Data System (ADS)
Shen, D.; Wang, J.; Cheng, X.; Rui, Y.; Ye, S.
2015-02-01
The rapid progress of Light Detection And Ranging (LiDAR) technology has made acquirement and application of high-resolution digital elevation model (DEM) data increasingly popular, especially with regards to the study of floodplain flow modeling. High-resolution DEM data include many redundant interpolation points, needs a high amount of calculation, and does not match the size of computational mesh. These disadvantages are a common problem for floodplain flow modeling studies. Two-dimensional (2-D) hydraulic modeling, a popular method of analyzing floodplain flow, offers high precision of elevation parameterization for computational mesh while ignoring much micro-topographic information of the DEM data itself. We offer a flood simulation method that integrates 2-D hydraulic model results and high-resolution DEM data, enabling the calculation of flood water levels in DEM grid cells through local inverse distance weighted interpolation. To get rid of the false inundation areas during interpolation, it employs the run-length encoding method to mark the inundated DEM grid cells and determine the real inundation areas through the run-length boundary tracing technique, which solves the complicated problem of the connectivity between DEM grid cells. We constructed a 2-D hydraulic model for the Gongshuangcha polder, a flood storage area of Dongting Lake, using our integrated method to simulate the floodplain flow. The results demonstrate that this method can solve DEM associated problems efficiently and simulate flooding processes with greater accuracy than DEM only simulations.
Confined liquid crystaline 5CB in 2D Thermodynamic Space - Preliminary Dielectric Relaxation Study
NASA Astrophysics Data System (ADS)
Pawlus, S.; Osinska, J.; Rzoska, S. J.; Kralj, S.; Cordoyiannis, G.
Results of preliminary broadband dielectric spectroscopy studies in a wide range of temperatures and pressures range for a mixture of rod-like liquid crystalline 4-cyano-4-pentylalkylbiphenyl (5CB) and hydrophilic silica spheres (Aerosil 300) are shown. Pretransitional anomaly, observed previously in the bulk 5CB, has been found. Temperature dynamics of the mixture was investigated with via the DC conductivity σ, coupled to the reorientational relaxation. The derivative based analysis of electric conductivity showed a clear non-Arrhenius dynamics and indicated the anomalous increase of the fragility strength coefficient on approaching the isotropic-nematic transition. Pressure investigations of the solidification from the nematic phase showed the increase of the transition temperature on pressuring but with unusual increasing of dT NS /dP coefficient.
NASA Astrophysics Data System (ADS)
Stone, James M.; Norman, Michael L.
1992-06-01
A detailed description of ZEUS-2D, a numerical code for the simulation of fluid dynamical flows including a self-consistent treatment of the effects of magnetic fields and radiation transfer is presented. Attention is given to the hydrodynamic (HD) algorithms which form the foundation for the more complex MHD and radiation HD algorithms. The effect of self-gravity on the flow dynamics is accounted for by an iterative solution of the sparse-banded matrix resulting from discretizing the Poisson equation in multidimensions. The results of an extensive series of HD test problems are presented. A detailed description of the MHD algorithms in ZEUS-2D is presented. A new method of computing the electromotive force is developed using the method of characteristics (MOC). It is demonstrated through the results of an extensive series of MHD test problems that the resulting hybrid MOC-constrained transport method provides for the accurate evolution of all modes of MHD wave families.
Adaptive clutter filter in 2-D color flow imaging based on in vivo I/Q signal.
Zhou, Xiaoming; Zhang, Congyao; Liu, Dong C
2014-01-01
Color flow imaging has been well applied in clinical diagnosis. For the high quality color flow images, clutter filter is important to separate the Doppler signals from blood and tissue. Traditional clutter filters, such as finite impulse response, infinite impulse response and regression filters, were applied, which are based on the hypothesis that the clutter signal is stationary or tissue moves slowly. However, in realistic clinic color flow imaging, the signals are non-stationary signals because of accelerated moving tissue. For most related papers, simulated RF signals are widely used without in vivo I/Q signal. Hence, in this paper, adaptive polynomial regression filter, which is down mixing with instantaneous clutter frequency, was proposed based on in vivo carotid I/Q signal in realistic color flow imaging. To get the best performance, the optimal polynomial order of polynomial regression filter and the optimal polynomial order for estimation of instantaneous clutter frequency respectively were confirmed. Finally, compared with the mean blood velocity and quality of 2-D color flow image, the experiment results show that adaptive polynomial regression filter, which is down mixing with instantaneous clutter frequency, can significantly enhance the mean blood velocity and get high quality 2-D color flow image. PMID:24211911
A 2-D oscillating flow analysis in Stirling engine heat exchangers
NASA Technical Reports Server (NTRS)
Ahn, Kyung H.; Ibrahim, Mounir B.
1991-01-01
A two-dimensional oscillating flow analysis was conducted, simulating the gas flow inside Stirling heat exchangers. Both laminar and turbulent oscillating pipe flow were investigated numerically for Re(max) = 1920 (Va = 80), 10800 (Va = 272), 19300 (Va = 272), and 60800 (Va = 126). The results are compared with experimental results of previous investigators. Also, predictions of the flow regime on present oscillating flow conditions were checked by comparing velocity amplitudes and phase differences with those from laminar theory and quasi-steady profile. A high Reynolds number k-epsilon turbulence model was used for turbulent oscillating pipe flow. Finally, performance evaluation of the K-epsilon model was made to explore the applicability of quasi-steady turbulent models to unsteady oscillating flow analysis.
A 2-D oscillating flow analysis in Stirling engine heat exchangers
NASA Technical Reports Server (NTRS)
Ahn, Kyung H.; Ibrahim, Mounir B.
1991-01-01
A two dimensional oscillating flow analysis was conducted, simulating the gas flow inside Stirling heat exchangers. Both laminar and turbulent oscillating pipe flow were investigated numerically for Re(max) = 1920 (Va = 80), 10800 (Va = 272), 19300 (Va = 272), and 60800 (Va = 126). The results are compared with experimental results of previous investigators. Also, predictions of the flow regime on present oscillating flow conditions were checked by comparing velocity amplitudes and phase differences with those from laminar theory and quasi-steady profile. A high Reynolds number k-epsilon turbulence model was used for turbulent oscillating pipe flow. Finally, performance evaluation of the K-epsilon model was made to explore the applicability of quasi-steady turbulent models to unsteady oscillating flow analysis.
NASA Astrophysics Data System (ADS)
Nelson, J. J.; Goldman, A. M.
2015-03-01
Metal insulator transitions are usually observed in high mobility and low carrier density 2D electron systems. There are several open questions regarding the metallic state including its existence in the limit of zero temperature. The current experimental focus is on the production of higher mobility samples to push the critical carrier density to even lower values, which will increase the effects of the Coulomb interaction. Here we report an unexpected result, the observation of the onset of a metallic state at high carrier densities in silicon gated with the ionic liquid DEME-TFSI. In addition we have observed a return to the insulating state as the carrier density was further increased. This reentrant insulting behavior is an effect that was recently predicted. Supported in part by NSF/DMR-1263316. Part of this work was carried out at the Minnesota Nanocenter.
Vibrational energy relaxation of the ND-stretching vibration of NH2D in liquid NH3.
Schäfer, Tim; Kandratsenka, Alexander; Vöhringer, Peter; Schroeder, Jörg; Schwarzer, Dirk
2012-09-01
The vibrational energy relaxation from the first excited ND-stretching mode of NH(2)D dissolved in liquid NH(3) is studied using molecular dynamics simulations. The rate constants for inter- and intramolecular energy transfer are calculated in the framework of the quantum-classical Landau-Teller theory. At 273 K and an ammonia density of 0.642 g cm(-3) the calculated ND-stretch lifetime of τ = 9.1 ps is in good agreement with the experimental value of 8.6 ps. The main relaxation channel accounting for 52% of the energy transfer involves an intramolecular transition to the first excited state of the umbrella mode. The energy difference between both states is taken up by the near-resonant bending vibrations of the solvent. Less important for the ND-stretch lifetime are both the direct transition to the ground state and intramolecular relaxation via the NH(2)D bending modes contributing 23% each. Our calculations imply that the experimentally observed weak density dependence of τ is caused by detuning the resonance between the ND-stretch-umbrella energy gap and the solvent accepting modes which counteracts the expected linear increase of the relaxation rate with density. PMID:22824981
NASA Astrophysics Data System (ADS)
Kelly, S. A.; Torres-Verdin, C.; Balhoff, M.
2014-12-01
Interest in liquid and interfacial behavior within nano-confinements spans many disciplines. Geophysical interest originates from a desire to understand flow mechanisms through hydrocarbon-rich nano-porous shale media, especially communication between fractures and the adjacent nano-porous matrix (imbibition). This work investigates the extent of boundary layer nucleation during polar liquid flows in hydrophilic nano-confinements via discrepancies seen in viscosity and capillary pressure from their bulk values. We perform our experiments in two-dimensional nanochannels of varying size and as small as 30 nm x 60 nm in cross section and still obtain visual data with reflected differential interference contrast (DIC) microscopy. The simple geometry of the nanochannels enables the comparison against analytical transport solutions. By designing a nanochannel experiment that allows us to monitor the rate of fluid imbibition and volume loss of a trapped air pocket the liquid is imbibing into, we are able to decouple capillary pressure and viscosity from imbibition data, as well as gain information about gas partitioning at the meniscus interface. Our current experiments are performed with organic solvents within siliceous nanochannels and the results of the decoupling scheme indicate that for rectangular nanochannels with heights of 60 nm and varying widths, effective viscosity is consistently between 4-12 times higher than the bulk value and capillary pressure is around 50% less than the macroscopic Young-Laplace equation prediction. These results equate to the nucleation of wall boundary layers on the order of tens of molecular layers thick. Structured boundary layers have an inherently increased viscosity compared to the liquid bulk value, resulting in a significant reduction in imbibition efficacy. This presence of approximately 15 nm boundary layers in on the threshold of two different theories - thin bimolecular boundary layers and exclusion zones (thick boundary
A comparative flow visualization study of thermocapillary flow in drops in liquid-liquid systems
NASA Technical Reports Server (NTRS)
Balasubramaniam, R.; Rashidnia, N.
1991-01-01
Experiments are performed to visualize thermocapillary flow in drops in an immiscible host liquid. The host liquid used is silicone oil. Drops of three different liquids are used, viz, vegetable oil, water-methanol mixture anad pure methanol. Clear evidence of thermocapillary flow is seen in vegetable oil drops. For a mixture of water and methanol (approximately 50-50 by weight), natural convection is seen to dominate the flow outside the drop. Pure methanol drops exhibit thermocapillary flow, but dissolve in silicone oil. A small amount of water added to pure methanol significantly reduces the dissolution. Flow oscillations occur in this system for both isothermal and non-isothermal conditions.
Geometry of thin liquid sheet flows
NASA Technical Reports Server (NTRS)
Chubb, Donald L.; Calfo, Frederick D.; Mcconley, Marc W.; Mcmaster, Matthew S.; Afjeh, Abdollah A.
1994-01-01
Incompresible, thin sheet flows have been of research interest for many years. Those studies were mainly concerned with the stability of the flow in a surrounding gas. Squire was the first to carry out a linear, invicid stability analysis of sheet flow in air and compare the results with experiment. Dombrowski and Fraser did an experimental study of the disintegration of sheet flows using several viscous liquids. They also detected the formulation of holes in their sheet flows. Hagerty and Shea carried out an inviscid stability analysis and calculated growth rates with experimental values. They compared their calculated growth rates with experimental values. Taylor studied extensively the stability of thin liquid sheets both theoretically and experimentally. He showed that thin sheets in a vacuum are stable. Brown experimentally investigated thin liquid sheet flows as a method of application of thin films. Clark and Dumbrowski carried out second-order stability analysis for invicid sheet flows. Lin introduced viscosity into the linear stability analysis of thin sheet flows in a vacuum. Mansour and Chigier conducted an experimental study of the breakup of a sheet flow surrounded by high-speed air. Lin et al. did a linear stability analysis that included viscosity and a surrounding gas. Rangel and Sirignano carried out both a linear and nonlinear invisid stability analysis that applies for any density ratio between the sheet liquid and the surrounding gas. Now there is renewed interest in sheet flows because of their possible application as low mass radiating surfaces. The objective of this study is to investigate the fluid dynamics of sheet flows that are of interest for a space radiator system. Analytical expressions that govern the sheet geometry are compared with experimental results. Since a space radiator will operate in a vacuum, the analysis does not include any drag force on the sheet flow.
A numerical method for computing unsteady 2-D boundary layer flows
NASA Technical Reports Server (NTRS)
Krainer, Andreas
1988-01-01
A numerical method for computing unsteady two-dimensional boundary layers in incompressible laminar and turbulent flows is described and applied to a single airfoil changing its incidence angle in time. The solution procedure adopts a first order panel method with a simple wake model to solve for the inviscid part of the flow, and an implicit finite difference method for the viscous part of the flow. Both procedures integrate in time in a step-by-step fashion, in the course of which each step involves the solution of the elliptic Laplace equation and the solution of the parabolic boundary layer equations. The Reynolds shear stress term of the boundary layer equations is modeled by an algebraic eddy viscosity closure. The location of transition is predicted by an empirical data correlation originating from Michel. Since transition and turbulence modeling are key factors in the prediction of viscous flows, their accuracy will be of dominant influence to the overall results.
2D and 3D potential flows with rotational source terms in turbomachines
NASA Astrophysics Data System (ADS)
Alkalai, K.; Leboeuf, F.
A computational method capable of treating two- and three-dimensional potential flows is developed which includes blade effects and viscosity in source terms determined over the entire flowfield considered. Details of the mathematical and numerical formulations are given, and grid generation and density calculation are discussed. Preliminary results obtained with the codes developed here are then presented, and the possibility of applying the method to more complex flows is examined.
Study of Unsteady Flow Actuation Produced by Surface Plasma Actuator on 2-D Airfoil
NASA Astrophysics Data System (ADS)
Phan, Minh Khang; Shin, Jichul
2014-10-01
Effect of flow actuation driven by low current continuous or pulsed DC surface glow discharge plasma actuator is studied. Schlieren image of induced flow on flat plate taken at a high repetition rate reveals that the actuation is mostly initiated near the cathode. Assuming that the actuation is mostly achieved by ions in the cathode sheath region, numerical model for the source of flow actuation is obtained by analytical estimation of ion pressure force created in DC plasma sheath near the cathode and added in momentum equation as a body force term. Modeled plasma flow actuator is simulated with NACA0012 airfoil oscillating over a certain range of angle of attack (AoA) at specific reduced frequencies of airfoil. By changing actuation authority according to the change in AoA, stabilization of unsteady flow field is improved and hence steady aerodynamic performance can be maintained. Computational result shows that plasma actuation is only effective in modifying aerodynamic characteristics of separated flow. It turns out that plasma pulse frequency should be tuned for optimal performance depending on phase angle and rotating speed. The actuation authority can be parameterized by a ratio between plasma pulse frequency and reduced frequency.
Du, Cheng-Feng; Shen, Nan-Nan; Li, Jian-Rong; Hao, Min-Ting; Wang, Zi; Huang, Xiao-Ying
2016-05-20
Presented are the ionothermal syntheses, characterizations, and properties of a series of two- and three-dimensional selenidostannate compounds synergistically directed by metal-amine complex (MAC) cations and ionic liquids (ILs) of [Bmmim]Cl (Bmmim=1-butyl-2,3-dimethylimidazolium). Four selenidostannates, namely, 2D-(Bmmim)3 [Ni(en)3 ]2 [Sn9 Se21 ]Cl (1, en=ethylenediamine), 2D-(Bmmim)8 [Ni2 (teta)2 (μ-teta)]Sn18 Se42 (2, teta=triethylenetetramine), 2D-(Bmmim)4 [Ni(tepa)Cl]2 [Ni(tepa)Sn12 Se28 ] (3, tepa=tetraethylenepentamine), and 3D-(Bmmim)2 [Ni(1,2-pda)3 ]Sn8 Se18 (4, 1,2-pda=1,2-diaminopropane), were obtained. Single-crystal X-ray diffraction analyses revealed that compounds 1 and 2 possess a lamellar anionic [Sn3 Se7 ]n (2n-) structure comprising distinct eight-membered ring units, whereas 3 features a MAC-decorated anionic [Ni(tepa)Sn12 Se28 ]n (6n-) layered structure. In contrast to 1-3, compound 4 exhibits a 3D open framework of anionic [Sn4 Se9 ]n (2n-) . The structural variation from 1 to 4 clearly indicates that on the basis of the synergistic structure-directing ability of the MACs and ILs, variation of the organic polyamine ligand has a significant impact on the formation of selenidostannates. PMID:27037731
An experimental study of flow separation over a flat plate with 2D transverse grooves
NASA Astrophysics Data System (ADS)
Jones, Emily Michelle
Nature has long been an inspiration for research in engineering. In particular, the biological surfaces of aquatic swimmers have been studied for their potential as drag reducing surfaces. The hydrodynamic benefit of riblets, or grooves embedded parallel to the flow, which appear on many aquatic biological surfaces, have been well documented and implemented in practical engineering applications. However the skin of dolphins is embedded with grooves that run perpendicular to the flow of water over their bodies. It is theorized that the transverse grooves present on dolphin skin trap vortices between them, creating a partial slip condition over the surface and inducing turbulence augmentation in the boundary layer, thus controlling boundary layer separation over the dolphin's skin. Similarly, sharks are covered with scales that are flexible at the base and capable of bristling, forming grooves running transverse to the flow. It is theorized that the scales bristle when encountering a reversing flow, thereby trapping vortices between the scales and, similarly, delaying boundary layer separation. In an attempt to test this hypothesis and study these affects, a spinning cylinder was used in a water tunnel to induce separation over a flat plate with 2 mm, rectangular transverse grooves and sinusoidal grooves of similar scaling. The results were compared to tripped, turbulent boundary layer separation occurring over a flat plate without grooves using time-resolved particle image velocimetry. The strength of the adverse pressure gradient was varied, and the observed delay in flow separation and other affects upon the boundary layer are discussed.
2D Flow patterning in Hele-Shaw configurations using Non-Uniform Electroosmotic Slip
NASA Astrophysics Data System (ADS)
Boyko, Evgeniy; Rubin, Shimon; Gat, Amir; Bercovici, Moran
2015-11-01
We present an analytical study, validated by numerical simulations, of electroosmotic flow in a Hele-Shaw configuration with non-uniform zeta potential distribution. Applying the lubrication approximation and assuming thin electric double layer, we derive a pair of uncoupled Poisson equations for the pressure and the stream function, and show that the inhomogeneous parts in these equations are governed by gradients in zeta potential parallel and perpendicular to the applied electric field, respectively. We obtain a solution for the case of a disk with uniform zeta potential and show that the flow field created is an exact dipole, even in the immediate vicinity of the disk. We then illustrate the ability to generate complex flow fields using superposition of such disks. Furthermore, we study the inverse problem in which we define the desired flow pattern and solve for the zeta potential distribution required in order to establish it. We demonstrate that such inverse problem solutions can be used to create directional flows confined within narrow regions, without physical walls. We show that these solutions can be assembled to create complex microfluidic networks, composed of intersecting channels and turns, which are basic building blocks in microfluidic devices.
NASA Astrophysics Data System (ADS)
Zhang, Wei; Markfort, Corey; Porté-Agel, Fernando
2014-05-01
Turbulent boundary-layer flows over complex topography have been extensively studied in the atmospheric sciences and wind engineering communities. The upwind turbulence level, the atmospheric thermal stability and the shape of the topography as well as surface characteristics play important roles in turbulent transport of momentum and scalar fluxes. However, to the best of our knowledge, atmospheric thermal stability has rarely been taken into account in laboratory simulations, particularly in wind-tunnel experiments. Extension of such studies in thermally-stratified wind tunnels will substantially advance our understanding of thermal stability effects on the physics of flow over complex topography. Additionally, high-resolution experimental data can be used for development of new parameterization of surface fluxes and validation of numerical models such as Large-Eddy Simulation (LES). A series of experiments of neutral and thermally-stratified boundary-layer flows over a wall-mounted 2-D block were conducted at the Saint Anthony Falls Laboratory boundary-layer wind tunnel. The 2-D block, with a width to height ratio of 2:1, occupied the lowest 25% of the turbulent boundary layer. Stable and convective boundary layers were simulated by independently controlling the temperature of air flow, the test section floor, and the wall-mounted block surfaces. Measurements using high-resolution Particle Image Velocimetry (PIV), x-wire/cold-wire anemometry, thermal-couples and surface heat flux sensors were made to quantify the turbulent properties and surface fluxes in distinct macroscopic flow regions, including the separation/recirculation zones, evolving shear layer and the asymptotic far wake. Emphasis will be put on addressing thermal stability effects on the spatial distribution of turbulent kinetic energy (TKE) and turbulent fluxes of momentum and scalar from the near to far wake region. Terms of the TKE budget equation are also inferred from measurements and
Untangling tracer trajectories and clarifying coherence in 2D flows using braid theory
NASA Astrophysics Data System (ADS)
Filippi, Margaux; Atis, Séverine; Thiffeault, Jean-Luc; Budišić, Marko; Allshouse, Michael; Peacock, Thomas
2014-11-01
Interpreting ocean surface transport is crucial to many areas of oceanography, ranging from marine ecology to pollution management. To better understand surface mixing, we investigate a braid theory method to detect transport barriers bounding coherent structures in two-dimensional fluid flows. Whereas most existing techniques rely on an extensive spatiotemporal knowledge of the flow field, we seek to identify these structures from sparse data sets involving trajectories of a few tracer particles or floats. We present the results of model and laboratory experimental studies to test the robustness and applicability of the braid theory method, and discuss the potential applicability to oceanic data sets.
Magnetic field applied to thermochemical non-equilibrium reentry flows in 2D - five species
NASA Astrophysics Data System (ADS)
Sávio de Góes Maciel, Edisson
2015-07-01
In this work, a study involving magnetic field actuation over reentry flows in thermochemical non-equilibrium is performed. The Euler and Navier-Stokes equations are studied. The proposed numerical algorithm is centred and second-order accurate. The hypersonic flow around a blunt body is simulated. Three time integration methods are tested. The reactive simulations involve Earth atmosphere of five species. The work of Gaitonde is the reference to couple the fluid dynamics and Maxwell equations of electromagnetism. The results have indicated that the Maciel scheme, using the Mavriplis dissipation model, yields the best prediction of the stagnation pressure.
NASA Astrophysics Data System (ADS)
Kolb, Evelyne; Algarra, Nicolas; Vandembroucq, Damien; Lazarus, Arnaud
2015-11-01
We propose a new fluid/structure interaction in the unusual case of a dense granular medium flowing against an elastic fibre acting as a flexible intruder. We experimentally studied the deflection of a mylar flexible beam clamped at one side, the other free side facing a 2D granular flow in a horizontal cell moving at a constant velocity. We investigated the reconfiguration of the fibre as a function of the fibre's rigidity and of the granular packing fraction close but below the jamming in 2D. Imposing the fibre geometry like its length or thickness sets the critical buckling force the fibre is able to resist if it was not supported by lateral grains, while increasing the granular packing fraction might laterally consolidate the fibre and prevent it from buckling. But on the other side, the approach to jamming transition by increasing the granular packing fraction will be characterized by a dramatically increasing size of the cluster of connected grains forming a solid block acting against the fibre, which might promote the fibre's deflection. Thus, we investigated the granular flow fields, the fibre's deflexion as well as the forces experienced by the fibre and compared them with theoretical predictions from elastica for different loadings along the fibre. PMMH, CNRS UMR 7636, UPMC, ESPCI-ParisTech, 10 rue Vauquelin, 75231 Paris Cedex 05, France.
NASA Astrophysics Data System (ADS)
Shen, D.; Wang, J.; Cheng, X.; Rui, Y.; Ye, S.
2015-08-01
The rapid progress of lidar technology has made the acquirement and application of high-resolution digital elevation model (DEM) data increasingly popular, especially in regards to the study of floodplain flow. However, high-resolution DEM data pose several disadvantages for floodplain modeling studies; e.g., the data sets contain many redundant interpolation points, large numbers of calculations are required to work with data, and the data do not match the size of the computational mesh. Two-dimensional (2-D) hydraulic modeling, which is a popular method for analyzing floodplain flow, offers highly precise elevation parameterization for computational mesh while ignoring much of the micro-topographic information of the DEM data itself. We offer a flood simulation method that integrates 2-D hydraulic model results and high-resolution DEM data, thus enabling the calculation of flood water levels in DEM grid cells through local inverse distance-weighted interpolation. To get rid of the false inundation areas during interpolation, it employs the run-length encoding method to mark the inundated DEM grid cells and determine the real inundation areas through the run-length boundary tracing technique, which solves the complicated problem of connectivity between DEM grid cells. We constructed a 2-D hydraulic model for the Gongshuangcha detention basin, which is a flood storage area of Dongting Lake in China, by using our integrated method to simulate the floodplain flow. The results demonstrate that this method can solve DEM associated problems efficiently and simulate flooding processes with greater accuracy than simulations only with DEM.
MEAN FLOW AND TURBULENCE MEASUREMENTS AROUND A 2-D ARRAY OF BUILDINGS IN A WIND TUNNEL
In order to predict the dispersion of harmful materials released in or near an urban environment, it is important to first understand the complex flow patterns which result from the interaction of the wind with buildings and, more commonly, clusters of buildings. Recent advanc...
Turbulence Measurements on a 2D NACA 0036 with Synthetic Jet Flow Control
NASA Technical Reports Server (NTRS)
Wilson, J. S.
2006-01-01
An active flow control experiment was conducted on a 2-ft chord NACA 0036 airfoil in a 3-ft by 4-ft Wind Tunnel at Re = 1 x 10(exp 6). The model was equipped with synthetic jet actuators at x/c = 0.30 and 0.65 that provided 120 Hz periodic excitation at a C(sub mu) 0.86% through 0.06-in wide slots. Three different slot con gurations were tested, including a baseline with no slots. Surface pressure data was collected to compare to previous tests and to combine with turbulence data to aid future CFD modeling efforts. Turbulence data, measured by hot-wire, was compared with and without flow control. Pressure data corroborates previous test data and provides more points for CFD validation. Hot-wire results showed ow control reduced the separated wake size and brought the high Reynolds stress shear layer closer to the airfoil surface. The position of this layer to the surface was altered more significantly than the magnitude of the peak stresses. Flow control was shown to increase turbulent energy in the attached boundary layer downstream of the slot but to have little effect upstream. These results provide further justification to continue assessing the potential of active flow control to reduce drag of helicopter airframe components.
NASA Astrophysics Data System (ADS)
Mechler, S.; Pershan, P. S.; Yahel, E.; Stoltz, S. E.; Shpyrko, O. G.; Lin, B.; Meron, M.; Sellner, S.
2010-10-01
The structural and mechanical properties of 2D crystalline surface phases that form at the surface of liquid eutectic Au82Si18 are studied using synchrotron x-ray scattering over a large temperature range. In the vicinity of the eutectic temperature the surface consists of a 2D atomic bilayer crystalline phase that transforms into a 2D monolayer crystalline phase during heating. The latter phase eventually melts into a liquidlike surface on further heating. We demonstrate that the short wavelength capillary wave fluctuations are suppressed due to the bending rigidity of 2D crystalline phases. The corresponding reduction in the Debye-Waller factor allows for measured reflectivity to be explained in terms of an electron density profile that is consistent with the 2D surface crystals.
Liquid hydrogen flow problems in Kiwi reactors
Thurston, R.S.
1992-09-01
The Kiwi series of reactors were the first ones tested in the US Rover Program in the development of nuclear rocket engines for space propulsion. The early experiments with liquid hydrogen showed that parallel flow systems were prone to uneven flow distributions and violent fluctuations in pressure and flow that were capable of destroying a reactor core. Kiwi flow distribution problems were solved by using multiple feed lines into the nozzle cooling system and carefully balancing impedance among them. The violent pressure and flow fluctuations were eliminated after their cause was identified as resonance phenomena driven by the response to flow disturbances of heat transfer through a superheated hydrogen layer. Smooth flow operations were assured by rapidly bringing operating pressures beyond several times the critical pressure of hydrogen. After this initial rough start, solid core nuclear rocket engines successfully passed milestones of achievements during the remainder of the Rover program.
NASA Astrophysics Data System (ADS)
Shaari, M. F.; Abu Bakar, H.; Nordin, N.; Saw, S. K.; Samad, Z.
2013-12-01
Contractile body is an alternative mechanism instead of rotating blade propeller to generate water jet for locomotion. The oscillating motion of the actuator at different frequencies varies the pressure and volume of the pressure chamber in time to draw in and jet out the water at a certain mass flow rate. The aim of this research was to analyze the influence of the actuating frequency of the fluid flow in the pressure chamber of the thruster during this inflation-deflation process. A 70mm × 70mm × 18mm (L × W × T) 2D water jet thruster was fabricated for this purpose. The contractile function was driven using two lateral pneumatic actuators where the fluid flow analysis was focused on the X-Y plane vector. Observation was carried out using a video camera and Matlab image measurement technique to determine the volume of the flowing mass. The result demonstrated that the greater actuating frequency decreases the fluid flow rate and the Reynolds number. This observation shows that the higher frequency would give a higher mass flow rate during water jet generation.
2D models of gas flow and ice grain acceleration in Enceladus' vents using DSMC methods
NASA Astrophysics Data System (ADS)
Tucker, Orenthal J.; Combi, Michael R.; Tenishev, Valeriy M.
2015-09-01
The gas distribution of the Enceladus water vapor plume and the terminal speeds of ejected ice grains are physically linked to its subsurface fissures and vents. It is estimated that the gas exits the fissures with speeds of ∼300-1000 m/s, while the micron-sized grains are ejected with speeds comparable to the escape speed (Schmidt, J. et al. [2008]. Nature 451, 685-688). We investigated the effects of isolated axisymmetric vent geometries on subsurface gas distributions, and in turn, the effects of gas drag on grain acceleration. Subsurface gas flows were modeled using a collision-limiter Direct Simulation Monte Carlo (DSMC) technique in order to consider a broad range of flow regimes (Bird, G. [1994]. Molecular Gas Dynamics and the Direct Simulation of Gas Flows. Oxford University Press, Oxford; Titov, E.V. et al. [2008]. J. Propul. Power 24(2), 311-321). The resulting DSMC gas distributions were used to determine the drag force for the integration of ice grain trajectories in a test particle model. Simulations were performed for diffuse flows in wide channels (Reynolds number ∼10-250) and dense flows in narrow tubular channels (Reynolds number ∼106). We compared gas properties like bulk speed and temperature, and the terminal grain speeds obtained at the vent exit with inferred values for the plume from Cassini data. In the simulations of wide fissures with dimensions similar to that of the Tiger Stripes the resulting subsurface gas densities of ∼1014-1020 m-3 were not sufficient to accelerate even micron-sized ice grains to the Enceladus escape speed. In the simulations of narrow tubular vents with radii of ∼10 m, the much denser flows with number densities of 1021-1023 m-3 accelerated micron-sized grains to bulk gas speed of ∼600 m/s. Further investigations are required to understand the complex relationship between the vent geometry, gas source rate and the sizes and speeds of ejected grains.
NASA Technical Reports Server (NTRS)
Seasholtz, Richard G.
1992-01-01
The use of molecular Rayleigh scattering for measurements of gas velocity and temperature is evaluated. Molecular scattering avoids problems associated with the seeding required by conventional laser anemometry and particle image velocimetry. The technique considered herein is based on the measurement of the spectrum of the scattered light. Planar imaging of Rayleigh scattering using a laser light sheet is evaluated for conditions at 30 km altitude (typical hypersonic flow conditions). The Cramer-Rao lower bounds for velocity and temperature measurement uncertainties are calculated for an ideal optical spectrum analyzer and for a planar mirror Fabry-Perot interferometer used in a static, imaging mode. With this technique, a single image of the Rayleigh scattered light from clean flows can be analyzed to obtain temperature and one component of velocity. Experimental results are presented for planar velocity measurements in a Mach 1.3 air jet.
SIMULATION REAL SCALE EXPERIMENT ON LEVEE BREACH USING 2D SHALLOW FLOW MODEL
NASA Astrophysics Data System (ADS)
Zenno, Hiroki; Iwasaki, Toshiki; Shimizu, Yasuyuki; Kimura, Ichiro
Flood in rivers is a common disaster all over the world. If a levee breach happens, it sometimes causes a fatal disaster. In addition, many buildings, urban facilities, lifelines, etc. are seriously damaged. Detailed mechanism of a levee breach has not been clarified yet. Therefore, it is important to predict the collapsing process of riverbank and behavior of overtop flow for reducing damage. We applied a two-dimensional shallow flow computational model to levee breach phenomena caused by overflow and the performance of the model was elucidated. A calibration of the numerical model is made through the comparison with field experimental data. Recently, a real-scale experiment on a levee breach was carried out at the Chiyoda Experimental Channel in Hokkaido, Japan. We performed the computation under the same conditions in the experiment. The computational results showed the excellent performance for simulating levee breach phenomena.
2D simulation of granular flow over irregular steep slopes using global and local coordinates
NASA Astrophysics Data System (ADS)
Juez, C.; Murillo, J.; García-Navarro, P.
2013-12-01
In this work approximate augmented Riemann solvers are formulated providing appropriate numerical schemes for mathematical models of granular flow on irregular steep slopes. Fluxes and source terms are discretized to ensure steady state configurations including correct modeling of start/stop flow conditions, both in a global and a local system of coordinates. The weak solutions presented involve the effect of bed slope in pressure distribution and frictional effects by means of the adequate gravity acceleration components. The numerical solvers proposed are first tested against 1D cases with exact solution and then their results are compared with experimental data in order to check the suitability of the mathematical models described in this work. Comparisons between results provided when using global and local system of coordinates are presented. The obtained results point out that both the global and the local system of coordinates can be used to predict faithfully the overall behavior of the phenomena considered in this work.
Flow transition with 2-D roughness elements in a 3-D channel
NASA Technical Reports Server (NTRS)
Liu, Zhining; Liu, Chaoquin; Mccormick, Stephen F.
1993-01-01
We develop a new numerical approach to study the spatially evolving instability of the streamwise dominant flow in the presence of roughness elements. The difficulty in handling the flow over the boundary surface with general geometry is removed by using a new conservative form of the governing equations and an analytical mapping. The numerical scheme uses second-order backward Euler in time, fourth-order central differences in all three spatial directions, and boundary-fitted staggered grids. A three-dimensional channel with multiple two-dimensional-type roughness elements is employed as the test case. Fourier analysis is used to decompose different Fourier modes of the disturbance. The results show that surface roughness leads to transition at lower Reynolds number than for smooth channels.
A High Order Discontinuous Galerkin Method for 2D Incompressible Flows
NASA Technical Reports Server (NTRS)
Liu, Jia-Guo; Shu, Chi-Wang
1999-01-01
In this paper we introduce a high order discontinuous Galerkin method for two dimensional incompressible flow in vorticity streamfunction formulation. The momentum equation is treated explicitly, utilizing the efficiency of the discontinuous Galerkin method The streamfunction is obtained by a standard Poisson solver using continuous finite elements. There is a natural matching between these two finite element spaces, since the normal component of the velocity field is continuous across element boundaries. This allows for a correct upwinding gluing in the discontinuous Galerkin framework, while still maintaining total energy conservation with no numerical dissipation and total enstrophy stability The method is suitable for inviscid or high Reynolds number flows. Optimal error estimates are proven and verified by numerical experiments.
Influence of flow topology on Lagrangian statistics in forced 2-D turbulence
NASA Astrophysics Data System (ADS)
Kadoch, Benjamin; Del-Castillo-Negrete, Diego; Bos, Wouter; Schneider, Kai
2010-11-01
Conditional Lagrangian statistics of forced two-dimensional turbulence in unbounded and bounded domains are studied by means of direct numerical simulation. The instantaneous flow domain is decomposed into either vorticity or strain dominated regions and a quiescent background region using the Okubo-Weiss criterion. The probability distribution function (PDF) of the residence time of the particles exhibits an exponential behavior in the background, while in the vorticity and strain dominated regions self-similar algebraic tails are found. For Lagrangian acceleration it is shown that both the vorticity and strain region are responsible for the heavy tails. Finally, the conditional PDFs of the curvature are found to be independent of the different flow domains yielding algebraic tails with slope close to -2, characteristic for an inverse chi-square distribution.
The 2-D and 3-D time marching transonic potential flow method for propfans
NASA Technical Reports Server (NTRS)
Williams, Marc H.
1988-01-01
Recent efforts concentrated on the development of aerodynamic tools for the analysis of rotors at transonic speeds and of configurations involving relative rotation. Three distinct approaches were taken: (1) extension of the lifting surface method of Williams and Hwang (1986) to relative rotation; (2) development of a time marching linear potential method for counter rotation; and (3) development of 2 and 3 dimensional finite volume potential flow schemes for single rotation. Results from each of these approaches are described.
Film flows and self-organized patterns of 2D-localized structures
Frenkel, A.L.
1996-12-31
Films flowing down an inclined plane are considered. An unconventional perturbation approach is discussed. It yields the most general evolution equation for film thickness and the least restrictive conditions for its validity. Results of numerical simulations of the dissipative-dispersive evolution equation indicate that novel, more complex type of spatiotemporal patterns can exist for strange attractors of nonequilibrium systems. It is suggested that real-life experiments satisfying the validity conditions of this theory are possible.
Symplectically invariant flow equations for N = 2, D = 4 gauged supergravity with hypermultiplets
NASA Astrophysics Data System (ADS)
Klemm, Dietmar; Petri, Nicolò; Rabbiosi, Marco
2016-04-01
We consider N = 2 supergravity in four dimensions, coupled to an arbitrary number of vector- and hypermultiplets, where abelian isometries of the quaternionic hyperscalar target manifold are gauged. Using a static and spherically or hyperbolically symmetric ansatz for the fields, a one-dimensional effective action is derived whose variation yields all the equations of motion. By imposing a sort of Dirac charge quantization condition, one can express the complete scalar potential in terms of a superpotential and write the action as a sum of squares. This leads to first-order flow equations, that imply the second-order equations of motion. The first-order flow turns out to be driven by Hamilton's characteristic function in the Hamilton-Jacobi formalism, and contains among other contributions the superpotential of the scalars. We then include also magnetic gaugings and generalize the flow equations to a symplectically covariant form. Moreover, by rotating the charges in an appropriate way, an alternative set of non-BPS first-order equations is obtained that corresponds to a different squaring of the action. Finally, we use our results to derive the attractor equations for near-horizon geometries of extremal black holes.
Flow behavior in liquid molding
NASA Technical Reports Server (NTRS)
Hunston, D.; Phelan, F.; Parnas, R.
1992-01-01
The liquid molding (LM) process for manufacturing polymer composites with structural properties has the potential to significantly lower fabrication costs and increase production rates. LM includes both resin transfer molding and structural reaction injection molding. To achieve this potential, however, the underlying science base must be improved to facilitate effective process optimization and implementation of on-line process control. The National Institute of Standards and Technology (NIST) has a major program in LM that includes materials characterization, process simulation models, on-line process monitoring and control, and the fabrication of test specimens. The results of this program are applied to real parts through cooperative projects with industry. The key feature in the effort is a comprehensive and integrated approach to the processing science aspects of LM. This paper briefly outlines the NIST program and uses several examples to illustrate the work.
Two-phase flow characteristics of liquid oxygen flow in low pressure liquid rocket engine
NASA Astrophysics Data System (ADS)
Cho, Namkyung; Kim, Seunghan; Kim, Youngmog; Jeong, Sangkwon; Jung, Jeheon
2004-06-01
In most cryogenic liquid rocket engines, liquid oxygen manifold and injector are not thermally insulated from room temperature environment for the purpose of reducing system complexity and weight. This feature of cryogenic liquid supply system results in the situation that liquid oxygen flow is vaporized especially in the vicinity of the manifold and the injector wall. The transient two-phase flow tendency is severe for low combustion pressure rocket engine without using turbo-pump. This paper focuses on the two-phase flow phenomena of liquid oxygen in low combustion pressure rocket engine. The KSR-III (Korea Sounding Rocket) engine test data is thoroughly analyzed to estimate the vapor fraction of liquid oxygen flow near the engine manifold and the injector. During the cold flow and the combustion tests of the KSR-III Engine, the static and dynamic pressures are measured at the engine inlet, the liquid oxygen manifold and the combustion chamber. The manifold outer wall and the inner wall temperatures are also measured. In this paper, we present the experimental investigation on the vapor generation, the vapor mass fraction, and the boiling characteristics of the liquid oxygen flow in the engine manifold and injector.
Analysis of High-Speed Rotating Flow in 2D Polar (r - θ)Coordinate
NASA Astrophysics Data System (ADS)
Pradhan, S.
2016-03-01
The generalized analytical model for the radial boundary layer in a high-speed rotating cylinder is formulated for studying the gas flow field due to insertion of mass, momentum and energy into the rotating cylinder in the polar (r - θ) plane. The analytical solution includes the sixth order differential equation for the radial boundary layer at the cylindrical curved surface in terms of master potential (χ) , which is derived from the equations of motion in a polar (r - θ) plane. The linearization approximation (Wood & Morton, J. Fluid Mech-1980; Pradhan & Kumaran, J. Fluid Mech-2011; Kumaran & Pradhan, J. Fluid Mech-2014) is used, where the equations of motion are truncated at linear order in the velocity and pressure disturbances to the base flow, which is a solid-body rotation. Additional assumptions in the analytical model include constant temperature in the base state (isothermal condition), and high Reynolds number, but there is no limitation on the stratification parameter. In this limit, the gas flow is restricted to a boundary layer of thickness (Re (1 / 3) R) at the wall of the cylinder. Here, the stratification parameter A = √ ((mΩ 2R2) / (2kB T)) . This parameter Ais the ratio of the peripheral speed, ΩR , to the most probable molecular speed, √(2 k_B T/m), the Reynolds number Re = (ρ _w ΩR2 / μ) , where m is the molecular mass, Ω and R are the rotational speed and radius of the cylinder, k_B is the Boltzmann constant, T is the gas temperature, ρ_w is the gas density at wall, and μ is the gas viscosity. The analytical solutions are then compared with direct simulation Monte Carlo (DSMC) simulations.
NASA Astrophysics Data System (ADS)
Nale, J. P.; Gosain, A. K.; Khosa, R.
2015-12-01
Pinder River, one of major headstreams of River Ganga, originates in Pindari Glaciers of Kumaon Himalayas and after passing through rugged gorges meets Alaknanda at Karanprayag forming one of the five celestial confluences of Upper Ganga region. While other sub-basins of Upper Ganga are facing severe ecological losses, Pinder basin is still in its virginal state and is well known for its beautiful valleys besides being host to unique and rare biodiversity. A proposed 252 MW run-of-river hydroelectric project at Devsari on this river has been a major concern on account of its perceived potential for egregious environmental and social impacts. In this context, the study presented tries to analyse the expected changes in aquatic habitat conditions after this project is operational (with different operation policies). SWAT hydrological modelling platform has been used to derive stream flow simulations under various scenarios ranging from the present to the likely future conditions. To analyse the habitat conditions, a two dimensional hydraulic-habitat model 'River-2D', a module of iRIC software, is used. Snow trout has been identified as the target keystone species and its habitat preferences, in the form of flow depths, flow velocity and substrate condition, are obtained from diverse sources of related literature and are provided as Habitat Suitability Indices to River-2D. Bed morphology constitutes an important River-2D input and has been obtained, for the designated 1 km long study reach of Pinder upto Karanprayag, from a combination of actual field observations and supplemented by SRTM 1 Arc-Second Global digital elevation data. Monthly Weighted Usable Area for three different life stages (Spawning, Juvenile and Adult) of Snow Trout are obtained corresponding to seven different flow discharges ranging from 10 cumec to 1000 cumec. Comparing the present and proposed future river flow conditions obtained from SWAT modelling, losses in Weighted Usable Area, for the
Manifest: A computer program for 2-D flow modeling in Stirling machines
NASA Technical Reports Server (NTRS)
Gedeon, David
1989-01-01
A computer program named Manifest is discussed. Manifest is a program one might want to use to model the fluid dynamics in the manifolds commonly found between the heat exchangers and regenerators of Stirling machines; but not just in the manifolds - in the regenerators as well. And in all sorts of other places too, such as: in heaters or coolers, or perhaps even in cylinder spaces. There are probably nonStirling uses for Manifest also. In broad strokes, Manifest will: (1) model oscillating internal compressible laminar fluid flow in a wide range of two-dimensional regions, either filled with porous materials or empty; (2) present a graphics-based user-friendly interface, allowing easy selection and modification of region shape and boundary condition specification; (3) run on a personal computer, or optionally (in the case of its number-crunching module) on a supercomputer; and (4) allow interactive examination of the solution output so the user can view vector plots of flow velocity, contour plots of pressure and temperature at various locations and tabulate energy-related integrals of interest.
Compartmentalized Droplets for Continuous Flow Liquid-Liquid Interface Catalysis.
Zhang, Ming; Wei, Lijuan; Chen, Huan; Du, Zhiping; Binks, Bernard P; Yang, Hengquan
2016-08-17
To address the limitations of batch organic-aqueous biphasic catalysis, we develop a conceptually novel method termed Flow Pickering Emulsion, or FPE, to process biphasic reactions in a continuous flow fashion. This method involves the compartmentalization of bulk water into micron-sized droplets based on a water-in-oil Pickering emulsion, which are packed into a column reactor. The compartmentalized water droplets can confine water-soluble catalysts, thus "immobilizing" the catalyst in the column reactor, while the interstices between the droplets allow the organic (oil) phase to flow. Key fundamental principles underpinning this method such as the oil phase flow behavior, the stability of compartmentalized droplets and the confinement capability of these droplets toward water-soluble catalysts are experimentally and theoretically investigated. As a proof of this concept, case studies including a sulfuric acid-catalyzed addition reaction, a heteropolyacid-catalyzed ring opening reaction and an enzyme-catalyzed chiral reaction demonstrate the generality and versatility of the FPE method. Impressively, in addition to the excellent durability, the developed FPE reactions exhibit up to 10-fold reaction efficiency enhancement in comparison to the existing batch reactions, indicating a unique flow interface catalysis effect. This study opens up a new avenue to allow conventional biphasic catalysis reactions to access more sustainable and efficient flow chemistry using an innovative liquid-liquid interface protocol. PMID:27429173
Thomas J. Hanratty
2005-02-25
A research program was carried out at the University of Illinois in which develops a scientific approach to gas-liquid flows that explains their macroscopic behavior in terms of small scale interactions. For simplicity, fully-developed flows in horizontal and near-horizontal pipes. The difficulty in dealing with these flows is that the phases can assume a variety of configurations. The specific goal was to develop a scientific understanding of transitions from one flow regime to another and a quantitative understanding of how the phases distribute for a give regime. These basic understandings are used to predict macroscopic quantities of interest, such as frictional pressure drop, liquid hold-up, entrainment in annular flow and frequency of slugging in slug flows. A number of scientific issues are addressed. Examples are the rate of atomization of a liquid film, the rate of deposition of drops, the behavior of particles in a turbulent field, the generation and growth of interfacial waves. The use of drag-reducing polymers that change macroscopic behavior by changing small scale interactions was explored.
2D transient granular flows over obstacles: experimental and numerical work
NASA Astrophysics Data System (ADS)
Juez, Carmelo; Caviedes-Voullième, Daniel; Murillo, Javier; García-Navarro, Pilar
2016-04-01
Landslides are an ubiquitous natural hazard, and therefore human infrastructure and settlements are often at risk in mountainous regions. In order to better understand and predict landslides, systematic studies of the phenomena need to be undertaken. In particular, computational tools which allow for analysis of field problems require to be thoroughly tested, calibrated and validated under controlled conditions. And to do so, it is necessary for such controlled experiments to be fully characterized in the same terms as the numerical model requires. This work presents an experimental study of dry granular flow over a rough bed with topography which resembles a mountain valley. It has an upper region with a very high slope. The geometry of the bed describes a fourth order polynomial curve, with a low point with zero slope, and afterwards a short region with adverse slope. Obstacles are present in the lower regions which are used as model geometries of human structures. The experiments consisted of a sudden release a mass of sand on the upper region, and allowing it to flow downslope. Furthermore, it has been frequent in previous studies to measure final states of the granular mass at rest, but seldom has transient data being provided, and never for the entire field. In this work we present transient measurements of the moving granular surfaces, obtained with a consumer-grade RGB-D sensor. The sensor, developed for the videogame industry, allows to measure the moving surface of the sand, thus obtaining elevation fields. The experimental results are very consistent and repeatable. The measured surfaces clearly show the distinctive features of the granular flow around the obstacles and allow to qualitatively describe the different flow patterns. More importantly, the quantitative description of the granular surface allows for benchmarking and calibration of predictive numerical models, key in scaling the small-scale experimental knowledge into the field. In addition, as
NASA Astrophysics Data System (ADS)
Filipović, Vilim; Romić, Davor; Romić, Marija; Matijević, Lana; Mallmann, Fábio J. K.; Robinson, David A.
2016-04-01
Growing vegetables commercially requires intensive management and involves high irrigation demands and input of agrochemicals. Plastic mulch application in combination with drip irrigation is a common agricultural management technique practiced due to variety of benefits to the crop, mostly vegetable biomass production. However, the use of these techniques can result in various impacts on water and nutrient distribution in underlying soil and consequently affect nutrient leaching towards groundwater resources. The aim of this work is to estimate the effect of plastic mulch cover in combination with drip irrigation on water and nitrate dynamics in soil using HYDRUS-2D model. The field site was located in Croatian costal karst area on a Gleysol (WRB). The experiment was designed according to the split-plot design in three repetitions and was divided into plots with plastic mulch cover (MULCH) and control plots with bare soil (CONT). Each of these plots received applications of three levels of nitrogen fertilizer: 70, 140, and 210 kg per ha. All plots were equipped with drip irrigation and cropped with bell pepper (Capsicum annuum L. cv. Bianca F1). Lysimeters were installed at 90 cm depth in all plots and were used for monitoring the water and nitrate outflow. HYDRUS-2D was used for modeling the water and nitrogen outflow in the MULCH and CONT plots, implementing the proper boundary conditions. HYDRUS-2D simulated results showed good fitting to the field site observed data in both cumulative water and nitrate outflow, with high level of agreement. Water flow simulations produced model efficiency of 0.84 for CONT and 0.56 for MULCH plots, while nitrate simulations showed model efficiency ranging from 0.67 to 0.83 and from 0.70 to 0.93, respectively. Additional simulations were performed with the absence of the lysimeter, revealing faster transport of nitrates below drip line in the CONT plots, mostly because of the increased surface area subjected to precipitation
2-D transmitral flows simulation by means of the immersed boundary method on unstructured grids
NASA Astrophysics Data System (ADS)
Denaro, F. M.; Sarghini, F.
2002-04-01
Interaction between computational fluid dynamics and clinical researches recently allowed a deeper understanding of the physiology of complex phenomena involving cardio-vascular mechanisms. The aim of this paper is to develop a simplified numerical model based on the Immersed Boundary Method and to perform numerical simulations in order to study the cardiac diastolic phase during which the left ventricle is filled with blood flowing from the atrium throughout the mitral valve. As one of the diagnostic problems to be faced by clinicians is the lack of a univocal definition of the diastolic performance from the velocity measurements obtained by Eco-Doppler techniques, numerical simulations are supposed to provide an insight both into the physics of the diastole and into the interpretation of experimental data. An innovative application of the Immersed Boundary Method on unstructured grids is presented, fulfilling accuracy requirements related to the development of a thin boundary layer along the moving immersed boundary. It appears that this coupling between unstructured meshes and the Immersed Boundary Method is a promising technique when a wide range of spatial scales is involved together with a moving boundary. Numerical simulations are performed in a range of physiological parameters and a qualitative comparison with experimental data is presented, in order to demonstrate that, despite the simplified model, the main physiological characteristics of the diastole are well represented. Copyright
Time-Dependent 2D Modeling of Magnetron Plasma Torch in Turbulent Flow
NASA Astrophysics Data System (ADS)
Li, Lincun; Xia, Weidong
2008-06-01
A theoretical model is presented to describe the electromagnetic, heat transfer and fluid flow phenomena within a magnetron plasma torch and in the resultant plume, by using a commercial computational fluid dynamics (CFD) code FLUENT. Specific calculations are presented for a pure argon system (i.e., an argon plasma discharging into an argon environment), operated in a turbulent mode. An important finding of this work is that the external axial magnetic field (AMF) may have a significant effect on the behavior of arc plasma and thus affects the resulting plume. The AMF impels the plasma to retract axially and expand radially. As a result, the plasma intensity distribution on the cross section of torch seems to be more uniform. Numerical results also show that with AMF, the highest plasma temperature decreases and the anode arc root moves upstream significantly, while the current density distribution at the anode is more concentrated with a higher peak value. In addition, the use of AMF then induces a strong backflow at the torch spout and its magnitude increases with the AMF strength but decreases with the inlet gas velocity.
NASA Astrophysics Data System (ADS)
Stone, James M.; Norman, Michael L.
1992-06-01
In this, the second of a series of three papers, we continue a detailed description of ZEUS-2D, a numerical code for the simulation of fluid dynamical flows in astrophysics including a self-consistent treatment of the effects of magnetic fields and radiation transfer. In this paper, we give a detailed description of the magnetohydrodynamical (MHD) algorithms in ZEUS-2D. The recently developed constrained transport (CT) algorithm is implemented for the numerical evolution of the components of the magnetic field for MHD simulations. This formalism guarantees the numerically evolved field components will satisfy the divergence-free constraint at all times. We find, however, that the method used to compute the electromotive forces must be chosen carefully to propagate accurately all modes of MHD wave families (in particular shear Alfvén waves). A new method of computing the electromotive force is developed using the method of characteristics (MOC). It is demonstrated through the results of an extensive series of MHD test problems that the resulting hybrid MOC-CT method provides for the accurate evolution of all modes of MHD wave families.
NASA Astrophysics Data System (ADS)
Kim, Ho Jun; Lee, Hae June
2016-06-01
The wide applicability of capacitively coupled plasma (CCP) deposition has increased the interest in developing comprehensive numerical models, but CCP imposes a tremendous computational cost when conducting a transient analysis in a three-dimensional (3D) model which reflects the real geometry of reactors. In particular, the detailed flow features of reactive gases induced by 3D geometric effects need to be considered for the precise calculation of radical distribution of reactive species. Thus, an alternative inclusive method for the numerical simulation of CCP deposition is proposed to simulate a two-dimensional (2D) CCP model based on the 3D gas flow results by simulating flow, temperature, and species fields in a 3D space at first without calculating the plasma chemistry. A numerical study of a cylindrical showerhead-electrode CCP reactor was conducted for particular cases of SiH4/NH3/N2/He gas mixture to deposit a hydrogenated silicon nitride (SiN x H y ) film. The proposed methodology produces numerical results for a 300 mm wafer deposition reactor which agree very well with the deposition rate profile measured experimentally along the wafer radius.
Rising of a single Taylor drop in a stagnant liquid—2D laminar flow and axisymmetry limits
NASA Astrophysics Data System (ADS)
Direito, F. J. N.; Campos, J. B. L. M.; Miranda, J. M.
2016-05-01
A numerical (computational fluid dynamics (CFD)) study concerning the rise of individual liquid Taylor drops through vertical columns of stagnant heavier liquids is presented in this paper. CFD simulations were performed in Ansys Fluent, using its implementation of volume of fluid method, assuming the flow to be axisymmetric and laminar. Different physical conditions were tested, corresponding to different combinations of relevant dimensionless parameters and the numerical method was validated through experimental data available in the literature. The viscosity ratio between the lighter and the heavier liquid was within the range 0.01-40 and Eötvös number was between 8 and 30. Morton number was within the interval of 2.32 × 10-6-100. Froude number results were compared to data from a literature correlation. The accordance is acceptable for the ranges studied. Velocity profiles in significant regions are reported (drop nose, drop bottom and continuous phase liquid film). The influence of changing one dimensionless parameter alone was assessed. For small and large viscosity ratios, axisymmetric behavior is not a valid assumption.
A study of thin liquid sheet flows
NASA Technical Reports Server (NTRS)
Chubb, Donald L.; Calfo, Frederick D.; Mcconley, Marc W.; Mcmaster, Matthew S.; Afjeh, Abdollah A.
1993-01-01
This study was a theoretical and experimental investigation of thin liquid sheet flows in vacuum. A sheet flow created by a narrow slit of width, W, coalesces to a point at a distance, L, as a result of surface tension forces acting at the sheet edges. As the flow coalesces, the fluid accumulates in the sheet edges. The observed triangular shape of the sheet agrees with the calculated triangular result. Experimental results for L/W as a function of Weber number, We, agree with the calculated result, L/W = the sq. root of 8We. The edge cross sectional shape is found to oscillate from elliptic to 'cigar' like to 'peanut' like and then back to elliptic in the flow direction. A theoretical one-dimensional model was developed that yielded only elliptic solutions for the edge cross section. At the points where the elliptic shapes occur, there is agreement between theory and experiment.
NASA Astrophysics Data System (ADS)
Llanes, F.; dela Resma, M.; Ferrer, P.; Realino, V.; Aquino, D. T.; Eco, R. C.; Lagmay, A.
2013-12-01
From November 14 to December 3, 2004, Luzon Island was ravaged by 4 successive typhoons: Typhoon Mufia, Tropical Storm Merbok, Tropical Depression Winnie, and Super Typhoon Nanmadol. Tropical Depression Winnie was the most destructive of the four when it triggered landslides on November 29 that devastated the municipalities of Infanta, General Nakar, and Real in Quezon Province, southeast Luzon. Winnie formed east of Central Luzon on November 27 before it moved west-northwestward over southeastern Luzon on November 29. A total of 1,068 lives were lost and more than USD 170 million worth of damages to crops and infrastructure were incurred from the landslides triggered by Typhoon Winnie on November 29 and the flooding caused by the 4 typhoons. FLO-2D, a flood routing software for generating flood and debris flow hazard maps, was utilized to simulate the debris flows that could potentially affect the study area. Based from the rainfall intensity-duration-frequency analysis, the cumulative rainfall from typhoon Winnie on November 29 which was approximately 342 mm over a 9-hour period was classified within a 100-year return period. The Infanta station of the Philippine Atmospheric Geophysical and Astronomical Services Administration (PAGASA) was no longer able to measure the amount of rainfall after this period because the rain gauge in that station was washed away by floods. Rainfall data with a 100-year return period was simulated over the watersheds delineated from a SAR-derived digital elevation model. The resulting debris flow hazard map was compared with results from field investigation and previous studies made on the landslide event. The simulation identified 22 barangays (villages) with a total of 45,155 people at risk of turbulent flow and flooding.
TITAN2D simulations of pyroclastic flows at Cerro Machín Volcano, Colombia: Hazard implications
NASA Astrophysics Data System (ADS)
Murcia, H. F.; Sheridan, M. F.; Macías, J. L.; Cortés, G. P.
2010-03-01
Cerro Machín is a dacitic tuff ring located in the central part of the Colombian Andes. It lies at the southern end of the Cerro Bravo-Cerro Machín volcanic belt. This volcano has experienced at least six major explosive eruptions during the last 5000 years. These eruptions have generated pyroclastic flows associated with Plinian activity that have traveled up to 8 km from the crater, and pyroclastic flows associated with Vulcanian activity with shorter runouts of 5 km from the source. Today, some 21,000 people live within a 8 km radius of Cerro Machín. The volcano is active with fumaroles and has shown increasing seismic activity since 2004, and therefore represents a potentially increasing threat to the local population. To evaluate the possible effects of future eruptions that may generate pyroclastic density currents controlled by granular flow dynamics we performed flow simulations with the TITAN2D code. These simulations were run in all directions around the volcano, using the input parameters of the largest eruption reported. The results show that an eruption of 0.3 km 3 of pyroclastic flows from a collapsing Plinian column would travel up to 9 km from the vent, emplacing a deposit thicker than 60 m within the Toche River valley. Deposits >45 m thick can be expected in the valleys of San Juan, Santa Marta, and Azufral creeks, while 30 m thick deposits could accumulate within the drainages of the Tochecito, Bermellón, and Coello Rivers. A minimum area of 56 km 2 could be affected directly by this kind of eruption. In comparison, Vulcanian column-collapse pyroclastic flows of 0.1 km 3 would travel up to 6 km from the vent depositing >45 m thick debris inside the Toche River valley and more than 30 m inside the valleys of San Juan, Santa Marta, and Azufral creeks. The minimum area that could be affected directly by this kind of eruption is 33 km 2. The distribution and thickness of the deposits obtained by these simulations are consistent with the hazard
NASA Astrophysics Data System (ADS)
Horritt, M. S.; Bates, P. D.; Mattinson, M. J.
2006-09-01
SummaryThe effects of mesh resolution and topographic data quality on the predictions of a 2D finite volume model of channel flow are investigated. 25 cm resolution side scan sonar swath bathymetry of a 7 km reach of the river Thames, UK, provides topography for a series of finite volume models with resolutions ranging from 2.5 to 50 m. Results from the coarser meshes are compared with the 2.5 m simulation which is used as a benchmark. The model shows greater sensitivity to mesh resolution than topographic sampling. Sensitivity to mesh resolution is attributed to two effects of roughly equal magnitude. Small elements are able to represent hydraulic features such as recirculation zones, and a more accurate representation of the domain boundary helps to drive these flow features. In practical terms, a models at a resolution of 20 and 50 m require 50 m cross-sections, whereas the 10 m model predictions are improved by using all the bathymetry data.
Turbulent diamagnetism in flowing liquid sodium.
Spence, E J; Nornberg, M D; Jacobson, C M; Parada, C A; Taylor, N Z; Kendrick, R D; Forest, C B
2007-04-20
The nature of Ohm's law is examined in a turbulent flow of liquid sodium. A magnetic field is applied to the flowing sodium, and the resulting magnetic field is measured. The mean velocity field of the sodium is also measured in an identical-scale water model of the experiment. These two fields are used to determine the terms in Ohm's law, indicating the presence of currents driven by a turbulent electromotive force. These currents result in a diamagnetic effect, generating magnetic field in opposition to the dominant fields of the experiment. The magnitude of the fluctuation-driven magnetic field is comparable to that of the field induced by the sodium's mean flow. PMID:17501423
NASA Astrophysics Data System (ADS)
Dages, Cecile; Samouelian, Anatja; Lanoix, Marthe; Dollinger, Jeanne; Chakkour, Sara; Chovelon, Gabrielle; Trabelsi, Khouloud; Voltz, Marc
2015-04-01
Ditches are involved in the transfer of pesticide to surface and groundwaters (e.g. Louchart et al., 2001). Soil horizons underlying ditch beds may present specific soil characteristics compared to neighbouring field soils due to erosion/deposition processes, to the specific biological activities (rooting dynamic and animal habitat) in the ditches (e.g. Vaughan et al., 2008) and to management practices (burning, dredging, mowing,...). Moreover, in contrast to percolation processes in field soils that can be assumed to be mainly 1D vertical, those occurring in the ditch beds are by essence 2D or even 3D. Nevertheless, due to a lake of knowledge, these specific aspects of transfer within ditch beds are generally omitted for hydrological simulation at the catchment scale (Mottes et al., 2014). Accordingly, the aims of this study were i) to characterize subsurface solute transfer through ditch beds and ii) to determine equivalent hydraulic parameters of the ditch beds for use in catchment scale hydrological simulations. A complementary aim was to evaluate the error in predictions performed when percolation in ditches is assumed to be similar to that in the neighbouring field soil. First, bromide transfer experiments were performed on undisturbed soil column (15 cm long with a 15 cm inner-diameter), horizontally and vertically sampled within each soil horizon underlying a ditch bed and within the neighboring field. Columns were sampled at the Roujan catchment (Hérault, France), which belongs to the long term Mediterranean hydrological observatory OMERE (Voltz and Albergel, 2002). Second, for each column, a set of parameters was determined by inverse optimization with mobile-immobile or dual permeability models, with CXTFIT (Toride et al., 1999) or with HYDRUS (Simunek et al., 1998). Third, infiltration and percolation in the ditch was simulated by a 2D flow domain approach considering the 2D variation in hydraulic properties of the cross section of a ditch bed. Last
Numerical model of water flow and solute accumulation in vertisols using HYDRUS 2D/3D code
NASA Astrophysics Data System (ADS)
Weiss, Tomáš; Dahan, Ofer; Turkeltub, Tuvia
2015-04-01
Keywords: dessication-crack-induced-salinization, preferential flow, conceptual model, numerical model, vadose zone, vertisols, soil water retention function, HYDRUS 2D/3D Vertisols cover a hydrologically very significant area of semi-arid regions often through which water infiltrates to groundwater aquifers. Understanding of water flow and solute accumulation is thus very relevant to agricultural activity and water resources management. Previous works suggest a conceptual model of dessication-crack-induced-salinization where salinization of sediment in the deep section of the vadose zone (up to 4 m) is induced by subsurface evaporation due to convective air flow in the dessication cracks. It suggests that the salinization is induced by the hydraulic gradient between the dry sediment in the vicinity of cracks (low potential) and the relatively wet sediment further from the main cracks (high potential). This paper presents a modified previously suggested conceptual model and a numerical model. The model uses a simple uniform flow approach but unconventionally prescribes the boundary conditions and the hydraulic parameters of soil. The numerical model is bound to one location close to a dairy farm waste lagoon, but the application of the suggested conceptual model could be possibly extended to all semi-arid regions with vertisols. Simulations were conducted using several modeling approaches with an ultimate goal of fitting the simulation results to the controlling variables measured in the field: temporal variation in water content across thick layer of unsaturated clay sediment (>10 m), sediment salinity and salinity the water draining down the vadose zone to the water table. The development of the model was engineered in several steps; all computed as forward solutions by try-and-error approach. The model suggests very deep instant infiltration of fresh water up to 12 m, which is also supported by the field data. The paper suggests prescribing a special atmospheric
NASA Astrophysics Data System (ADS)
LeVeque, R. J.; Motley, M. R.
2015-12-01
A series of tsunami wave basin experiments of flow through a scale model of Seaside, Oregon have been used as validation data for a 2015 benchmarking workshop hosted by the National Tsunami Mitigation Program, which focused on better understanding the ability of tsunami models to predict flow velocities and inundation depths following a coastal inundation event. As researchers begin to assess the safety of coastal infrastructures, proper assessment of tsunami-induced forces on coastal structures is critical. Hydrodynamic forces on these structures are fundamentally proportional to the local momentum flux of the fluid, and experimental data included momentum flux measurements at many instrumented gauge locations. The GeoClaw tsunami model, which solves the two-dimensional shallow water equations, was compared against other codes during the benchmarking workshop, and more recently a three-dimensional computational fluid dynamics model using the open-source OpenFOAM software has been developed and results from this model are being compared with both the experimental data and the 2D GeoClaw results. In addition, the 3D model allows for computation of fluid forces on the faces of structures, permitting an investigation of the common use of momentum flux as a proxy for these forces. This work aims to assess the potential to apply these momentum flux predictions locally within the model to determine tsunami-induced forces on critical structures. Difficulties in working with these data sets and cross-model comparisons will be discussed. Ultimately, application of the more computationally efficient GeoClaw model, informed by the 3D OpenFOAM models, to predict forces on structures at the community scale can be expected to improve the safety and resilience of coastal communities.
Origin of Surface-Driven Passive Liquid Flows.
Yd, Sumith; Maroo, Shalabh C
2016-08-30
Passive liquid flow occurs in nature in the transport of water up tall trees and is desired for high-heat flux removal in thermal management devices. Typically, liquid-vapor surface tension is used to generate passive flows (e.g., capillary and Marangoni flows). In this work, we perform a fundamental molecular study on passive liquid flow driven by the solid-liquid surface tension force. Such surface tension values are first estimated by placing a liquid film over the surface and simulating various surface temperatures, followed by which simulations are performed by differential heating of the liquid film over the surface. Very strong passive liquid flows are obtained that lead to steady-state, continuous, and high-heat flux removal close to the maximum theoretical limit, as predicted by the kinetic theory of evaporation. Nondimensional empirical relations are developed for surface tension gradient, flow velocity, and evaporation rate. PMID:27483012
Stability of Thin Liquid Sheet Flows
NASA Technical Reports Server (NTRS)
McConley, Marc W.; Chubb, Donald L.; McMaster, Matthew S.; Afjeh, Abdollah A.
1997-01-01
A two-dimensional, linear stability analysis of a thin nonplanar liquid sheet flow in vacuum is carried out. A sheet flow created by a narrow slit of W and tau attains a nonplanar cross section as a consequence of cylinders forming on the sheet edge under the influence of surface tension forces. The region where these edge cylinders join the sheet is one of high curvature, and this is found to be the location where instability is most likely to occur. The sheet flow is found to be unstable, but with low growth rates for symmetric wave disturbances and high growth rates for antisymmetric disturbances. By combining the symmetric and antisymmetric disturbance modes, a wide range of stability characteristics is obtained. The product of unstable growth rate and flow time is proportional to the width-to-thickness ratio of the sift generating the sheet Three-dimensional effects can alter these results, particularly when the sheet length-to-width ratio is not much greater than unity.
Flow Induced Electrification of Liquid Insulated Systems.
NASA Astrophysics Data System (ADS)
Washabaugh, Andrew Patrick
1995-01-01
The transport or motion of semi-insulating liquids has led to flow induced static electrification and catastrophic failures in several industries. While techniques for reducing the hazard have been developed, the roles of seemingly important parameters are poorly understood. The objective of this thesis was to measure and understand the fundamental parameters of the flow electrification process that, together with the laws of electroquasistatics and physicochemical hydrodynamics, can be used to predict the performance of complex flow systems, with particular attention to transformer applications. A rotating cylindrical electrode apparatus, which provided cylindrical Couette flow, was used to simulate flow electrification in an electric power transformer. The apparatus had Shell Diala A transformer oil filling the annulus between coaxial cylindrical stainless steel electrodes that were either bare metal, or covered by a thin copper sheet and/or EHV-Weidmann HiVal pressboard insulation. Extensive experiments characterized the time transient and steady state behavior of the electrification through measurements of the volume charge density, the terminal voltage, and the terminal current as the system was driven out of equilibrium by changes in the flow rate (inner cylinder rotation rates of 100-1400 rpm, Reynolds numbers of 5 times 10^3-5 times 10^5), temperature (15-70 ^circ), insulation moisture content (0.5-20 ppm in the oil), applied voltage (0-2 kV DC), and concentration of the non-ionizable anti-static additive 1,2,3 benzotriazole (BTA, 0-60 ppm). Generally, the electrification increased with flow rate and temperature but the BTA appeared to cause competing effects: it decreased the volume charge density on the liquid side of the interface (by a factor of 4), which reduces the electrification, but also decreased the oil conductivity (by a factor of 10), which enhances the electrification. A critical oil BTA concentration of 5 -8 ppm minimized the electrification
Flow of liquids in surface grooves
Rye, R.R.; Yost, F.G.; Mann, J.A. Jr.
1996-01-24
We have obtained detailed capillary kinetic data for flow of a series of alcohols with various surface tension to viscosity ratios, {gamma}/{mu}, spreading in open V-shaped grooves cut in Cu with three different groove angles. Two theoretical models which assume Poiseuille flow and static advancing contact angles were tested against the experimental data. One is a detailed hydrodynamic model with the basic driving force resulting from the pressure drop across a curved interface. The second depends on the total interfacial energy change, independent of the shape of the liquid interface. Both agree with the experimental data. Both predict numerical values in general agreement with experiment and with each other. In the threshold region where the transition occurs between filled and empty regions of the groove, the liquid height decreases linearly with distance, within experimental limitations, and forms an angle which roughly scales as the contact angle for a significant fraction of the threshold region. On the basis of the present detailed experimental data for both kinetics and threshold profile, the differences between experiment and theory and between the theoretical models are insufficient to allow a clear choice between the models. 20 refs., 11 figs., 3 tabs.
NASA Astrophysics Data System (ADS)
Tochikubo, Fumiyoshi; Aoki, Takuya; Shirai, Naoki; Uchida, Satoshi
2015-09-01
In the application of atmospheric-pressure discharges in contact with liquid, primary reactions are initiated between radicals and liquid molecules at plasma-liquid interface. Since the diffusion in the liquid is very slow, some convective flow is necessary to exchange the chemicals at the plasma-liquid interface for the efficient reactions. In our previous work, we found the appearance of specific downward flow in the liquid just below the dc glow discharge in contact with liquid. This downflow will be effective for exchanging the chemicals at plasma-liquid interface. In this work, we investigated the characteristics of liquid flow induced by atmospheric-pressure dc glow discharge with liquid electrode in detail; the influence of voltage polarity, current amplitude, liquid conductivity, the electrode arrangement, and so on. The spatiotemporal development of liquid flow was visualized by schlieren method, and the temperature distribution was measured using temperature-sensitive liquid crystal particles dispersed in the liquid. The liquid-flow characteristics was reproduced by a fluid simulation considering a downward driving force at liquid surface from plasma. The candidate of the driving force will be the momentum transfer of charged species at the liquid surface. This work is partly supported by JSPS KAKENHI Grant Number 15H03584.
Material Flows in an Active Nematic Liquid Crystal
NASA Astrophysics Data System (ADS)
Decamp, Stephen; Redner, Gabriel; Baskaran, Aparna; Hagan, Michael; Dogic, Zvonimir
Active matter systems are composed of energy consuming constituent components which drive far-from-equilibrium dynamics. As such, active materials exhibit energetic states which would be unfavorable in passive, equilibrium materials. We study one such material; an active nematic liquid crystal which exists in a dynamical steady state where +/-1/2 defects are continuously generated and annihilated at a constant rate. The active nematic is composed of micron-sized microtubule filaments which are highly concentrated into a quasi-2D film that resides on an oil-water interface. Kinesin motor proteins drive inter-filament sliding which results in net extensile motion of the microtubule film. Notably, we find a mesophase in which motile +1/2 defects, acquire system-spanning orientational order. Currently, we are tracking material flows generated by the active stresses in the system to measure length scales at which energy is dissipated, and to measure the relation between internally generated flows and bend in the nematic field.
Fluid flow from a low to a higher density liquid
NASA Astrophysics Data System (ADS)
Weinberg, F.
1984-12-01
The penetration of liquid from a low density brine solution into a higher density solution below it has been measured as a function of vertical flow velocity and the density difference of the two solutions. The flow velocity was produced by a horizontal disc rotating in the low density liquid. The results show the penetration distance and penetration rate are dependent on flow velocity and in particular are very sensitive to small changes in the density difference between the two liquids. The observations are considered in relation to liquid penetration into dendritic arrays, and fluid flow in the pool of ingots and continuously cast steel billets, during solidification.
Drop impact on flowing liquid films: asymmetric splashing
NASA Astrophysics Data System (ADS)
Ismail, Renad; Che, Zhizhao; Rotkovitz, Lauren; Adebayo, Idris; Matar, Omar
2015-11-01
The splashing of droplets on flowing liquid films is studied experimentally using high-speed photography. The flowing liquid films are generated on an inclined substrate. The flow rate of the liquid film, the inclination angle, and the droplet speed are controlled and their effects on the splashing process studied. Due to the flow in the liquid film and the oblique impact direction, the splashing process is asymmetric. The propagation of the asymmetric crown and the generation of secondary droplets on the rim of the crown are analysed through image processing. The results show that the flow in the liquid films significantly affects the propagation of the liquid crown and the generation of secondary droplets. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.
NASA Astrophysics Data System (ADS)
Magri, F.; Inbar, N.; Raggad, M.; Möller, S.; Siebert, C.; Möller, P.; Kuehn, M.
2014-12-01
Lake Kinneret (Lake Tiberias or Sea of Galilee) is the most important freshwater reservoir in the Northern Jordan Valley. Simulations that couple fluid flow, heat and mass transport are built to understand the mechanisms responsible for the salinization of this important resource. Here the effects of permeability distribution on 2D and 3D convective patterns are compared. 2D simulations indicate that thermal brine in Haon and some springs in the Yamourk Gorge (YG) are the result of mixed convection, i.e. the interaction between the regional flow from the bordering heights and thermally-driven flow (Magri et al., 2014). Calibration of the calculated temperature profiles suggests that the faults in Haon and the YG provides paths for ascending hot waters, whereas the fault in the Golan recirculates water between 1 and 2 km depths. At higher depths, faults induce 2D layered convection in the surrounding units. The 2D assumption for a faulted basin can oversimplify the system, and the conclusions might not be fully correct. The 3D results also point to mixed convection as the main mechanism for the thermal anomalies. However, in 3D the convective structures are more complex allowing for longer flow paths and residence times. In the fault planes, hydrothermal convection develops in a finger regime enhancing inflow and outflow of heat in the system. Hot springs can form locally at the surface along the fault trace. By contrast, the layered cells extending from the faults into the surrounding sediments are preserved and are similar to those simulated in 2D. The results are consistent with the theory from Zhao et al. (2003), which predicts that 2D and 3D patterns have the same probability to develop given the permeability and temperature ranges encountered in geothermal fields. The 3D approach has to be preferred to the 2D in order to capture all patterns of convective flow, particularly in the case of planar high permeability regions such as faults. Magri, F., et al., 2014
Stability of erythrocyte suspensions layered on stationary and flowing liquids
NASA Technical Reports Server (NTRS)
Omenyi, S. N.; Rhodes, P. H.; Snyder, R. S.
1982-01-01
The apparent stability of erythrocyte suspensions layered on stationary and flowing Ficoll solutions was studied considering the effects of particle concentration, type and size, and the different flow rates of the particle suspensions and chamber liquid. The data from the flowing system were empirically fitted and, when extrapolated to zero chamber liquid flow rate, gave values comparable to the data from the stationary system, thus confirming the validity of the data and our approach to obtain that data.
Brinzer, Thomas; Berquist, Eric J; Ren, Zhe; Dutta, Samrat; Johnson, Clinton A; Krisher, Cullen S; Lambrecht, Daniel S; Garrett-Roe, Sean
2015-06-01
The CO2ν3 asymmetric stretching mode is established as a vibrational chromophore for ultrafast two-dimensional infrared (2D-IR) spectroscopic studies of local structure and dynamics in ionic liquids, which are of interest for carbon capture applications. CO2 is dissolved in a series of 1-butyl-3-methylimidazolium-based ionic liquids ([C4C1im][X], where [X](-) is the anion from the series hexafluorophosphate (PF6 (-)), tetrafluoroborate (BF4 (-)), bis-(trifluoromethyl)sulfonylimide (Tf2N(-)), triflate (TfO(-)), trifluoroacetate (TFA(-)), dicyanamide (DCA(-)), and thiocyanate (SCN(-))). In the ionic liquids studied, the ν3 center frequency is sensitive to the local solvation environment and reports on the timescales for local structural relaxation. Density functional theory calculations predict charge transfer from the anion to the CO2 and from CO2 to the cation. The charge transfer drives geometrical distortion of CO2, which in turn changes the ν3 frequency. The observed structural relaxation timescales vary by up to an order of magnitude between ionic liquids. Shoulders in the 2D-IR spectra arise from anharmonic coupling of the ν2 and ν3 normal modes of CO2. Thermal fluctuations in the ν2 population stochastically modulate the ν3 frequency and generate dynamic cross-peaks. These timescales are attributed to the breakup of ion cages that create a well-defined local environment for CO2. The results suggest that the picosecond dynamics of CO2 are gated by local diffusion of anions and cations. PMID:26049445
NASA Astrophysics Data System (ADS)
Brinzer, Thomas; Berquist, Eric J.; Ren, Zhe; Dutta, Samrat; Johnson, Clinton A.; Krisher, Cullen S.; Lambrecht, Daniel S.; Garrett-Roe, Sean
2015-06-01
The CO2ν3 asymmetric stretching mode is established as a vibrational chromophore for ultrafast two-dimensional infrared (2D-IR) spectroscopic studies of local structure and dynamics in ionic liquids, which are of interest for carbon capture applications. CO2 is dissolved in a series of 1-butyl-3-methylimidazolium-based ionic liquids ([C4C1im][X], where [X]- is the anion from the series hexafluorophosphate (PF 6- ), tetrafluoroborate (BF 4- ), bis-(trifluoromethyl)sulfonylimide (Tf2N-), triflate (TfO-), trifluoroacetate (TFA-), dicyanamide (DCA-), and thiocyanate (SCN-)). In the ionic liquids studied, the ν3 center frequency is sensitive to the local solvation environment and reports on the timescales for local structural relaxation. Density functional theory calculations predict charge transfer from the anion to the CO2 and from CO2 to the cation. The charge transfer drives geometrical distortion of CO2, which in turn changes the ν3 frequency. The observed structural relaxation timescales vary by up to an order of magnitude between ionic liquids. Shoulders in the 2D-IR spectra arise from anharmonic coupling of the ν2 and ν3 normal modes of CO2. Thermal fluctuations in the ν2 population stochastically modulate the ν3 frequency and generate dynamic cross-peaks. These timescales are attributed to the breakup of ion cages that create a well-defined local environment for CO2. The results suggest that the picosecond dynamics of CO2 are gated by local diffusion of anions and cations.
Sokolowsky, Kathleen P; Bailey, Heather E; Hoffman, David J; Andersen, Hans C; Fayer, Michael D
2016-07-21
Two-dimensional infrared (2D IR) data are presented for a vibrational probe in three nematogens: 4-cyano-4'-pentylbiphenyl, 4-cyano-4'-octylbiphenyl, and 4-(trans-4-amylcyclohexyl)-benzonitrile. The spectral diffusion time constants in all three liquids in the isotropic phase are proportional to [T*/(T - T*)](1/2), where T* is 0.5-1 K below the isotropic-nematic phase transition temperature (TNI). Rescaling to a reduced temperature shows that the decays of the frequency-frequency correlation function (FFCF) for all three nematogens fall on the same curve, suggesting a universal dynamic behavior of nematogens above TNI. Spectral diffusion is complete before significant orientational relaxation in the liquid, as measured by optically heterodyne detected-optical Kerr effect (OHD-OKE) spectroscopy, and before any significant orientational randomization of the probe measured by polarization selective IR pump-probe experiments. To interpret the OHD-OKE and FFCF data, we constructed a mode coupling theory (MCT) schematic model for the relationships among three correlation functions: ϕ1, a correlator for large wave vector density fluctuations; ϕ2, the orientational correlation function whose time derivative is the observable in the OHD-OKE experiment; and ϕ3, the FFCF for the 2D IR experiment. The equations for ϕ1 and ϕ2 match those in the previous MCT schematic model for nematogens, and ϕ3 is coupled to the first two correlators in a straightforward manner. Resulting models fit the data very well. Across liquid crystals, the temperature dependences of the coupling constants show consistent, nonmonotonic behavior. A remarkable change in coupling occurs at ∼5 K above TNI, precisely where the rate of spectral diffusion in 5CB was observed to deviate from that of a similar nonmesogenic liquid. PMID:27363680
Brinzer, Thomas; Berquist, Eric J.; Ren, Zhe; Dutta, Samrat; Johnson, Clinton A.; Krisher, Cullen S.; Lambrecht, Daniel S.; Garrett-Roe, Sean
2015-06-07
The CO{sub 2}ν{sub 3} asymmetric stretching mode is established as a vibrational chromophore for ultrafast two-dimensional infrared (2D-IR) spectroscopic studies of local structure and dynamics in ionic liquids, which are of interest for carbon capture applications. CO{sub 2} is dissolved in a series of 1-butyl-3-methylimidazolium-based ionic liquids ([C{sub 4}C{sub 1}im][X], where [X]{sup −} is the anion from the series hexafluorophosphate (PF{sub 6}{sup −}), tetrafluoroborate (BF{sub 4}{sup −}), bis-(trifluoromethyl)sulfonylimide (Tf{sub 2}N{sup −}), triflate (TfO{sup −}), trifluoroacetate (TFA{sup −}), dicyanamide (DCA{sup −}), and thiocyanate (SCN{sup −})). In the ionic liquids studied, the ν{sub 3} center frequency is sensitive to the local solvation environment and reports on the timescales for local structural relaxation. Density functional theory calculations predict charge transfer from the anion to the CO{sub 2} and from CO{sub 2} to the cation. The charge transfer drives geometrical distortion of CO{sub 2}, which in turn changes the ν{sub 3} frequency. The observed structural relaxation timescales vary by up to an order of magnitude between ionic liquids. Shoulders in the 2D-IR spectra arise from anharmonic coupling of the ν{sub 2} and ν{sub 3} normal modes of CO{sub 2}. Thermal fluctuations in the ν{sub 2} population stochastically modulate the ν{sub 3} frequency and generate dynamic cross-peaks. These timescales are attributed to the breakup of ion cages that create a well-defined local environment for CO{sub 2}. The results suggest that the picosecond dynamics of CO{sub 2} are gated by local diffusion of anions and cations.
NASA Astrophysics Data System (ADS)
Ben Ali, Karim; Lafon, Olivier; Zimmermann, Herbert; Guittet, Eric; Lesot, Philippe
2007-08-01
We describe several homo- and heteronuclear 2D NMR strategies dedicated to the analysis of anisotropic 2H spectra of a mixture of dideuterated unlike/like stereoisomers with two remote stereogenic centers, using weakly orienting chiral liquid crystals. To this end, we propose various 2D correlation experiments, denoted "D(H) nD" or "D(H) nC" (with n = 1, 2), that involve two heteronuclear polarization transfers of INEPT-type with one or two proton relays. The analytical expressions of correlation signals for four pulse sequences reported here were calculated using the product-operators formalism for spin I = 1 and S = 1/2. The features and advantages of each scheme are presented and discussed. The efficiency of these 2D sequences is illustrated using various deuterated model molecules, dissolved in organic solutions of polypeptides made of poly- γ-benzyl- L-glutamate (PBLG) or poly- ɛ-carbobenzyloxy- L-lysine (PCBLL) and NMR numerical simulations.
Synthesis of electroactive ionic liquids for flow battery applications
Anderson, Travis Mark; Ingersoll, David; Staiger, Chad; Pratt, Harry
2015-09-01
The present disclosure is directed to synthesizing metal ionic liquids with transition metal coordination cations, where such metal ionic liquids can be used in a flow battery. A cation of a metal ionic liquid includes a transition metal and a ligand coordinated to the transition metal.
Slip flow of diverse liquids on robust superomniphobic surfaces.
Wu, Yang; Cai, Meirong; Li, Zhenquan; Song, Xinwang; Wang, Hongyan; Pei, Xiaowei; Zhou, Feng
2014-01-15
Water slips exist over superhydrophobic solid surfaces, but the slip flow of diverse liquids on a single surface has not been deliberately studied to date. Here, we report the slip flow behavior of a variety of liquids with different surface tensions and viscosities on a robust omniphobic surface. This surface displayed a dramatic slippage effect and thus a high drag reduction efficiency of approximately 10-20% for all liquids, depending on both liquid viscosity and surface energy. The observed liquid slip was attributed to the surface dual micro/nanostructure and the low-surface-energy coating. PMID:24231078
Tamimi, Amr; Fayer, Michael D
2016-07-01
The room-temperature ionic liquid EmimNTf2 (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) was studied with two-dimensional infrared (2D IR) spectroscopy and polarization selective pump-probe (PSPP) experiments using low-concentration selenocyanate (SeCN(-)) as the vibrational probe. SeCN(-) was added as EmimSeCN, which keeps the cation the same. KSeCN was also used, so K(+) was added. Two 2D IR polarization configurations were employed: ⟨XXXX⟩ (all pulses have the same polarization) and ⟨XXYY⟩ (the first two pulse polarizations are perpendicular to that of the third pulse and the echo). The spectral diffusion differs for the two configurations, demonstrating that reorientation-induced spectral diffusion, in addition to structural spectral diffusion (SSD), plays a role in the observed dynamics. The SSD was extracted from the 2D IR time-dependent data. The samples with EmimSeCN have dynamics on several fast time scales; however, when KSeCN is used, both the PPSP anisotropy decay and the 2D IR decays have low amplitude offsets (nondecaying values at long times). The size of the offsets increased with increased K(+) concentration. These results are explained in terms of a two-ensemble model. A small fraction of the SeCN(-) is located in the regions modified by the presence of K(+), causing a substantial slowing of the SeCN(-) orientational relaxation and spectral diffusion. Having a small ensemble of SeCN(-) that undergoes very slow dynamics is sufficient to explain the offsets. For the major ensemble, the dynamics with and without K(+) are the same. PMID:26872207
Capillary-Driven Flow in Liquid Filaments Connecting Orthogonal Channels
NASA Technical Reports Server (NTRS)
Allen, Jeffrey S.
2005-01-01
Capillary phenomena plays an important role in the management of product water in PEM fuel cells because of the length scales associated with the porous layers and the gas flow channels. The distribution of liquid water within the network of gas flow channels can be dramatically altered by capillary flow. We experimentally demonstrate the rapid movement of significant volumes of liquid via capillarity through thin liquid films which connect orthogonal channels. The microfluidic experiments discussed provide a good benchmark against which the proper modeling of capillarity by computational models may be tested. The effect of surface wettability, as expressed through the contact angle, on capillary flow will also be discussed.
Two-phase liquid-liquid flows generated by impinging liquid jets
NASA Astrophysics Data System (ADS)
Tsaoulidis, Dimitrios; Li, Qi; Angeli, Panagiota
2015-11-01
Two-phase flows in intensified small-scale systems find increasing applications in (bio)chemical analysis and synthesis, fuel cells, polymerisation, and separation processes (solvent extraction). Current nuclear spent fuel reprocessing separation technologies have been developed many decades ago and have not taken account recent advances on process intensification which can drive down plant size and economics. In this work, intensified impinging jets will be developed to create dispersions by bringing the two liquid phases into contact through opposing small channels. A systematic set of experiments has been undertaken, to investigate the hydrodynamic characteristics, to develop predictive models, and enable comparisons with other contactors. Drop size distribution and mixing intensity will be investigated for liquid-liquid mixtures as a function of various parameters using high speed imaging and conductivity probes.
Liquid jet pumps for two-phase flows
Cunningham, R.G.
1995-06-01
Isothermal compression of a bubbly secondary fluid in a mixing-throat and diffuser is described by a one-dimensional flow model of a liquid-jet pump. Friction-loss coefficients used in the four equations may be determined experimentally, or taken from the literature. The model reduces to the liquid-jet gas compressor case if the secondary liquid is zero. Conversely, a zero secondary-gas flow reduces the liquid-jet gas and liquid (LJGL) model to that of the familiar liquid-jet liquid pump. A ``jet loss`` occurs in liquid-jet pumps if the nozzle tip is withdrawn from the entrance plane of the throat, and jet loss is included in the efficiency equations. Comparisons are made with published test data for liquid-jet liquid pumps and for liquid-jet gas compressors. The LJGL model is used to explore jet pump responses to two-phase secondary flows, nozzle-to-throat area ratio, and primary-jet velocity. The results are shown in terms of performance curves versus flow ratios. Predicted peak efficiencies are approximately 50 percent. Under sever operating conditions, LJGL pump performance curves exhibit maximum-flow ratios or cut-offs. Cut-offs occurs when two-phase secondary-flow steams attain sonic values at the entry of the mixing throat. A dimensionless number correlates flow-ratio cut-offs with pump geometry and operating conditions. Throat-entry choking of the secondary flow can be predicted, hence avoided, in designing jet pumps to hand two-phase fluids.
Pacht, J.A.; Brooks, L.; Messa, F.
1995-12-31
Carbonate debris flow are very important plays in Leonard strata along the northwestern margin of the Midland Basin. Delineation of these strata, however, is difficult and detailed stratigraphic analysis of both 2D and 3D seismic data is important in reducing risk. Porous debris flows are best developed during lowstand time. When sea-level falls to a point at or below the shelf margin, sand to boulder-sized clasts created by reef-front erosion are funneled through slope gullies onto the base of the slope. Large debris flows exhibit well-defined mounds which downlap onto the sequence boundary. Many of these flows, however, are too thin to exhibit discrete reflections. 3D seismic data are used to define subtle changes in amplitude and frequency which suggest presence of porous strata. Along the northwest shelf, porous debris flows exhibit lower amplitude (dim spots) and lower frequency than surrounding strata. They are commonly developed immediately downdip of major slump scars.
Liquid film flow in a fracture between two porous blocks
Dindoruk, B.; Firoozabadi, A. )
1994-12-01
Liquid film flow in a fracture between two porous bodies is mainly driven by pressure. The pressure drop across such a small distance could be significant. The flow of a liquid film is governed by the pressure drop across the fracture space, and therefore, understanding of liquid film flow in a single liquid bridge along a solid wall between two porous bodies is needed. The shape of the liquid bridge between the porous blocks is an unknown. The first step is to determine the shape of the free surface. Due to the nature of the problem, a boundary integral technique is found to provide the solution to the whole problem. Solutions are reported for a range of capillary numbers observed in cracked porous media. Pressure drop is correlated using a dimensionless capillary number group. Using analogy from the Darcy flow in porous media, a correlation for the equivalent Darcy permeability is developed.
Scaglione, S; Wendt, D; Miggino, S; Papadimitropoulos, A; Fato, M; Quarto, R; Martin, I
2008-08-01
In this study, we investigated the effect of the long-term (10 days) application of a defined and uniform level of fluid flow (uniform shear stress of 1.2 x 10(-3) N/m(2)) on human bone marrow stromal cells (BMSC) cultured on different substrates (i.e., uncoated glass or calcium phosphate coated glass, Osteologictrade mark) in a 2D parallel plate model. Both exposure to flow and culture on Osteologic significantly reduced the number of cell doublings. BMSC cultured under flow were more intensely stained for collagen type I and by von Kossa for mineralized matrix. BMSC exposed to flow displayed an increased osteogenic commitment (i.e., higher mRNA expression of cbfa-1 and osterix), although phenotype changes in response to flow (i.e., mRNA expression of osteopontin, osteocalcin and bone sialoprotein) were dependent on the substrate used. These findings highlight the importance of the combination of physical forces and culture substrate to determine the functional state of differentiating osteoblastic cells. The results obtained using a simple and controlled 2D model system may help to interpret the long-term effects of BMSC culture under perfusion within 3D porous scaffolds, where multiple experimental variables cannot be easily studied independently, and shear stresses cannot be precisely computed. PMID:17969030
Gas/liquid flow measurement using coriolis-based flow meters
Liu, K.T.; Nguyen, T.V.
1991-07-09
This patent describes a method of determining total mass flow rate and phase distribution of individual components in a flowing gas/liquid stream. It comprises flowing at least a first gas/liquid stream through a Coriolis-based flow meter, the first gas/liquid stream having a first known total mass flow rate and component phase distribution; obtaining a first apparent total mass flow rate output and a first apparent density output from the Coriolis- based mass flow meter; correlating the first known total mass flow rate and phase distribution with the first apparent mass flow rate output and the first apparent density output obtained from the Coriolis-based mass flow meter to determine a set of correlation equations; flowing a second gas/liquid stream through the Coriolis-based mass flow meter; obtaining a second apparent mass flow rate output and a second apparent density output from the Coriolis-based mass flow meter; calculating a total mass flow rate and a component phase distribution of the second gas/liquid stream based on the correlation equations and the second apparent mass flow rate output and the second apparent density output.
NASA Astrophysics Data System (ADS)
Decaix, J.; Alligné, S.; Nicolet, C.; Avellan, F.; Münch, C.
2015-12-01
1D hydro-electric models are useful to predict dynamic behaviour of hydro-power plants. Regarding vortex rope and cavitation surge in Francis turbines, the 1D models require some inputs that can be provided by numerical simulations. In this paper, a 2D cavitating Venturi is considered. URANS computations are performed to investigate the dynamic behaviour of the cavitation sheet depending on the frequency variation of the outlet pressure. The results are used to calibrate and to assess the reliability of the 1D models.
2015-01-01
In this work we investigate the interplay between flow and boundary condition effects on the orientation field of a thermotropic nematic liquid crystal under flow and confinement in a microfluidic device. Two types of experiments were performed using synchrotron small-angle X-ray-scattering (SAXS). In the first, a nematic liquid crystal flows through a square-channel cross section at varying flow rates, while the nematic director orientation projected onto the velocity/velocity gradient plane is measured using a 2D detector. At moderate-to-high flow rates, the nematic director is predominantly aligned in the flow direction, but with a small tilt angle of ∼±11° in the velocity gradient direction. The director tilt angle is constant throughout most of the channel width but switches sign when crossing the center of the channel, in agreement with the Ericksen–Leslie–Parodi (ELP) theory. At low flow rates, boundary conditions begin to dominate, and a flow profile resembling the escaped radial director configuration is observed, where the director is seen to vary more smoothly from the edges (with homeotropic alignment) to the center of the channel. In the second experiment, hydrodynamic focusing is employed to confine the nematic phase into a sheet of liquid sandwiched between two layers of Triton X-100 aqueous solutions. The average nematic director orientation shifts to some extent from the flow direction toward the liquid boundaries, although it remains unclear if one tilt angle is dominant through most of the nematic sheet (with abrupt jumps near the boundaries) or if the tilt angle varies smoothly between two extreme values (∼90 and 0°). The technique presented here could be applied to perform high-throughput measurements for assessing the influence of different surfactants on the orientation of nematic phases and may lead to further improvements in areas such as boundary lubrication and clarifying the nature of defect structures in LC displays. PMID
Silva, Bruno F B; Zepeda-Rosales, Miguel; Venkateswaran, Neeraja; Fletcher, Bretton J; Carter, Lester G; Matsui, Tsutomu; Weiss, Thomas M; Han, Jun; Li, Youli; Olsson, Ulf; Safinya, Cyrus R
2015-04-14
In this work we investigate the interplay between flow and boundary condition effects on the orientation field of a thermotropic nematic liquid crystal under flow and confinement in a microfluidic device. Two types of experiments were performed using synchrotron small-angle X-ray-scattering (SAXS). In the first, a nematic liquid crystal flows through a square-channel cross section at varying flow rates, while the nematic director orientation projected onto the velocity/velocity gradient plane is measured using a 2D detector. At moderate-to-high flow rates, the nematic director is predominantly aligned in the flow direction, but with a small tilt angle of ∼±11° in the velocity gradient direction. The director tilt angle is constant throughout most of the channel width but switches sign when crossing the center of the channel, in agreement with the Ericksen-Leslie-Parodi (ELP) theory. At low flow rates, boundary conditions begin to dominate, and a flow profile resembling the escaped radial director configuration is observed, where the director is seen to vary more smoothly from the edges (with homeotropic alignment) to the center of the channel. In the second experiment, hydrodynamic focusing is employed to confine the nematic phase into a sheet of liquid sandwiched between two layers of Triton X-100 aqueous solutions. The average nematic director orientation shifts to some extent from the flow direction toward the liquid boundaries, although it remains unclear if one tilt angle is dominant through most of the nematic sheet (with abrupt jumps near the boundaries) or if the tilt angle varies smoothly between two extreme values (∼90 and 0°). The technique presented here could be applied to perform high-throughput measurements for assessing the influence of different surfactants on the orientation of nematic phases and may lead to further improvements in areas such as boundary lubrication and clarifying the nature of defect structures in LC displays. PMID
Phase-locked measurements of gas-liquid horizontal flows
NASA Astrophysics Data System (ADS)
Zadrazil, Ivan; Matar, Omar; Markides, Christos
2014-11-01
A flow of gas and liquid in a horizontal pipe can be described in terms of various flow regimes, e.g. wavy stratified, annular or slug flow. These flow regimes appear at characteristic gas and liquid Reynolds numbers and feature unique wave phenomena. Wavy stratified flow is populated by low amplitude waves whereas annular flow contains high amplitude and long lived waves, so called disturbance waves, that play a key role in a liquid entrainment into the gas phase (droplets). In a slug flow regime, liquid-continuous regions travel at high speeds through a pipe separated by regions of stratified flow. We use a refractive index matched dynamic shadowgraphy technique using a high-speed camera mounted on a moving robotic linear rail to track the formation and development of features characteristic for the aforementioned flow regimes. We show that the wave dynamics become progressively more complex with increasing liquid and gas Reynolds numbers. Based on the shadowgraphy measurements we present, over a range of conditions: (i) phenomenological observations of the formation, and (ii) statistical data on the downstream velocity distribution of different classes of waves. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.
Hasegawa, H; Nakamura, A; Shinohara, Y; Baba, S
1997-02-21
A high-performance liquid chromatographic procedure has been developed for the determination of [D-Ala2,D-Leu5]enkephalin (DADLE) and the fragments containing D-leucine in rat blood. The procedure was applied to the determination of blood levels of [3H-D-Leu5]DADLE and the C-terminal fragments after intravenous administration of [3H-D-Leu5]DADLE to a rat. Unlabelled DADLE and the C-terminal fragments were spiked as carriers to rat blood samples and the blood samples were extracted with 1% trifluoroacetic acid in methanol. The recoveries from rat blood were quantitative for all compounds. DADLE and the C-terminal four fragments were well separated on a reversed-phase column with gradient elution using a mobile phase composed of 0.14% HClO4 and acetonitrile. PMID:9080313
Effect of surface texture and liquid property on the liquid film flow on an inclined wall
NASA Astrophysics Data System (ADS)
Kato, M.; Iso, Y.; Huang, J.; Matsuno, S.
2013-10-01
Liquid film flow used for separation processes such as absorption is required to increase thegas-liquid interfacial area in order to improve the separation performance. Furthermore, the low liquid loading in absorption processes is effective for the economic performance. Liquid film with low liquid loading, however, breaks up to rivulet flow, as well as reduces its interfacial area between gas and liquid. The present study focuses on detailed descriptions of the transition phenomena betweenfilm flow andrivulet flow by varying not only liquid flow rate but also liquid properties, as well as how such phenomena are affected by wall surface texture treatments. Results obtained by Computational Fluid Dynamics (CFD) with the Volume of Fluid (VOF) model are validated by lab-scale experiments. The results of CFD show that a wavy surface is effective to prevent the liquid film break-up. Correlation equations for the wetted area ratio are derived as functions of the dimensionless parameters Weber number, Reynolds number, Froude number and the liquid contact angle.
CFD Analysis for Flow of Liquids in Coils
NASA Astrophysics Data System (ADS)
Bandyopadhyay, Tarun Kanti; Das, Sudip Kumar
2016-04-01
The effects of liquid flow rate, coil diameter, pseudo plasticity of the liquids on the frictional pressure drop for the flow through helical coils have been reported through experimental investigation. Numerical modeling is carried using Fluent 6.3 software to find its applicability in the flow system. The Computational Fluid Dynamics (CFD) simulations are carried out using laminar non-Newtonian pseudo plastic power law model for laminar flow and k-ɛ model for turbulent flow for water. Water and dilute solution of Sodium Carboxy Methyl Cellulose (SCMC) as a non-Newtonian pseudo plastic fluid used for the study. Both hexahedral and tetrahedral grids are used for this simulation. The CFD results show the very good agreement with the experimental values. The comparison of the non-Newtonian liquid flow and water are also reported.
Sewage sludge dewatering using flowing liquid metals
Carlson, Larry W.
1986-01-01
A method and apparatus for reducing the moisture content of a moist sewage sludge having a moisture content of about 50% to 80% and formed of small cellular micro-organism bodies having internally confined water is provided. A hot liquid metal is circulated in a circulation loop and the moist sewage sludge is injected in the circulation loop under conditions of temperature and pressure such that the confined water vaporizes and ruptures the cellular bodies. The vapor produced, the dried sludge, and the liquid metal are then separated. Preferably, the moist sewage sludge is injected into the hot liquid metal adjacent the upstream side of a venturi which serves to thoroughly mix the hot liquid metal and the moist sewage sludge. The venturi and the drying zone after the venturi are preferably vertically oriented. The dried sewage sludge recovered is available as a fuel and is preferably used for heating the hot liquid metal.
Tranchida, Peter Q; Franchina, Flavio A; Zoccali, Mariosimone; Bonaccorsi, Ivana; Cacciola, Francesco; Mondello, Luigi
2013-09-01
The present contribution is focused on the measurement of the analytical sensitivity attained in untargeted/targeted MS/MS experiments, performed using flow-modulator comprehensive 2D and 1D GC. The comprehensive 2D experiment was performed by diverting part of the high flow (circa 80%) to flush the accumulation loop (about 28 mL/min) to waste, to reduce the gas flow entering the ion source. 1D analyses were performed through: (i) unmodulated and (ii) single column applications. An equivalent temperature program was applied in the modulated and unmodulated analyses, while a faster one was employed in the single column one. In all application types, the (same) triple quadrupole instrument was operated in the full-scan and multiple reaction monitoring modes. A genuine sweet orange oil and the same sample spiked with 20 phytosanitary compounds were employed to reach the research objective. The results highlight the problems related to the flow modulation-MS combination. Specifically, it was found that sensitivity was on average three to four times higher in unmodulated and optimized single-column applications. PMID:23868497
Thaw flow control for liquid heat transport systems
Kirpich, Aaron S.
1989-01-01
In a liquid metal heat transport system including a source of thaw heat for use in a space reactor power system, the thaw flow throttle or control comprises a fluid passage having forward and reverse flow sections and a partition having a plurality of bleed holes therein to enable fluid flow between the forward and reverse sections. The flow throttle is positioned in the system relatively far from the source of thaw heat.
Large Flow Birefringence of Nematogenic Bent-Core Liquid Crystals
Bailey, C.; Fodor-Csorba, K; Verduzco, R; Gleeson, J; Sprunt, S; Jakli, A
2009-01-01
We have found that bent-core liquid crystalline materials show exceptionally large intrinsic flow birefringence in their isotropic liquid phase. This effect is more than 100 times larger than typical values measured for low molecular weight liquid crystals. The specific flow birefringence (i.e., normalized by the flow viscosity) is an order of magnitude larger than in both side-chain polymeric as well as low molecular weight liquid crystals. We propose that this large enhancement for bent-core compounds may be attributed to nanoscale smecticlike clusters that persist above the nematic-isotropic transition temperature, and shear align under shear flow; however, this mechanism has not yet been definitively confirmed.
Two-Phase Acto-Cytosolic Fluid Flow in a Moving Keratocyte: A 2D Continuum Model.
Nikmaneshi, M R; Firoozabadi, B; Saidi, M S
2015-09-01
The F-actin network and cytosol in the lamellipodia of crawling cells flow in a centripetal pattern and spout-like form, respectively. We have numerically studied this two-phase flow in the realistic geometry of a moving keratocyte. Cytosol has been treated as a low viscosity Newtonian fluid flowing through the high viscosity porous medium of F-actin network. Other involved phenomena including myosin activity, adhesion friction, and interphase interaction are also discussed to provide an overall view of this problem. Adopting a two-phase coupled model by myosin concentration, we have found new accurate perspectives of acto-cytosolic flow and pressure fields, myosin distribution, as well as the distribution of effective forces across the lamellipodia of a keratocyte with stationary shape. The order of magnitude method is also used to determine the contribution of forces in the internal dynamics of lamellipodia. PMID:26403420
An IPOT meshless method using DC PSE approximation for fluid flow equations in 2D and 3D geometries
NASA Astrophysics Data System (ADS)
Bourantas, G. C.; Loukopoulos, V. C.; Skouras, E. D.; Burganos, V. N.; Nikiforidis, G. C.
2016-06-01
Navier-Stokes (N-S) equations, in their primitive variable (u-v-p) formulation, are numerically solved using the Implicit Potential (IPOT) numerical scheme in the context of strong form Meshless Point Collocation (MPC) method. The unknown field functions are computed using the Discretization Correction Particle Strength Exchange (DC PSE) approximation method. The latter makes use of discrete moment conditions to derive the operator kernels, which leads to low condition number for the moment matrix compared to other meshless interpolation methods and increased stability for the numerical solution. The proposed meshless scheme is applied on 2D and 3D spatial domains, using uniform or irregular set of nodes to represent the domain. The numerical results obtained are compared against those obtained using well-established methods.
VFLOW2D - A Vorte-Based Code for Computing Flow Over Elastically Supported Tubes and Tube Arrays
WOLFE,WALTER P.; STRICKLAND,JAMES H.; HOMICZ,GREGORY F.; GOSSLER,ALBERT A.
2000-10-11
A numerical flow model is developed to simulate two-dimensional fluid flow past immersed, elastically supported tube arrays. This work is motivated by the objective of predicting forces and motion associated with both deep-water drilling and production risers in the oil industry. This work has other engineering applications including simulation of flow past tubular heat exchangers or submarine-towed sensor arrays and the flow about parachute ribbons. In the present work, a vortex method is used for solving the unsteady flow field. This method demonstrates inherent advantages over more conventional grid-based computational fluid dynamics. The vortex method is non-iterative, does not require artificial viscosity for stability, displays minimal numerical diffusion, can easily treat moving boundaries, and allows a greatly reduced computational domain since vorticity occupies only a small fraction of the fluid volume. A gridless approach is used in the flow sufficiently distant from surfaces. A Lagrangian remap scheme is used near surfaces to calculate diffusion and convection of vorticity. A fast multipole technique is utilized for efficient calculation of velocity from the vorticity field. The ability of the method to correctly predict lift and drag forces on simple stationary geometries over a broad range of Reynolds numbers is presented.
NASA Astrophysics Data System (ADS)
Abdusslam, Saleh N.; Chit, Ong J.; Hamdan, Megat M.; Omar, Ashraf A.; Asrar, Waqar
2006-12-01
Fluid flows within turbomachinery tend to be extremely complex. Understanding such flows is crucial in the effort to improve current turbomachinery designs. Hence, computational approaches can be used to great advantage in this regard. In this paper, gas-kinetic BGK (Bhatnagar-Gross-Krook) scheme is developed for simulating compressible inviscid flow around a linear turbine cascade. BGK scheme is an approximate Riemann solver that uses the collisional Boltzmann equation as the governing equation for flow evolutions. For efficient computations, particle distribution functions in the general solution of the BGK model are simplified and used for the flow simulations. Second-order accuracy is achieved via the reconstruction of flow variables using the MUSCL (Monotone Upstream-Centered Schemes for Conservation Laws) interpolation technique together with a multistage Runge-Kutta method. A multi-zone H-type mesh for the linear turbine cascades is generated using a structured algebraic grid generation method. Computed results are compared with available experimental data and found to be in agreement with each other. In order to further substantiate the performance of the BGK scheme, another test case, namely a wedge cascade, is used. The numerical solutions obtained via this test are validated against analytical solutions, which showed to be in good agreement.
Confinement and flow of microscopic defects in layered liquids
NASA Astrophysics Data System (ADS)
Shojaei-Zadeh, Shahab
The term layered liquid applies to a broad range of materials containing anisotropic molecules that arrange themselves in parallel stacks. Examples are concentrated surfactant solutions, block copolymers, bio-membranes, liquid crystalline polymers, and liquid crystals. Due to the solid-like nature of these materials, microscopic defects form when their parallel layer structure is disturbed by external forces, surface interactions, or geometrical confinement. Unlike in solid crystals, defects formed here can flow and we show that the presence of defects changes the flow characteristics of these materials. In this work, we first introduce three different methods for using surface treatments to control the size and ordering of a particular class of defects known as focal conics: within closed PDMS microchannels, on PDMS surfaces covered with nanoscale cracks, and within ordered microcavities formed in PDMS films. We then examine the flow behavior of these defects in microchannels, using both surface tension differences and pressure gradients to drive the flow. A microfluidic network is designed and developed to enable more precise control over the pressure driven flow. Driving flow within this microfluidic network enables simultaneous visualization of the defect texture evolution and measurement of the pressure gradient-flow rate relationship. Our measurements show that the flow properties of layered liquids under confinement are different from their bulk, possibly due to the interaction of defects with each other and with the flow itself.
NASA Astrophysics Data System (ADS)
Alligné, S.; Decaix, J.; Nicolet, C.; Avellan, F.; Münch, C.
2015-12-01
The 1D modelling of cavitation vortex rope dynamics in Francis turbine draft tube is decisive for prediction of pressure fluctuations in the system. However, models are defined with parameters which values must be quantified either experimentally or numerically. In this paper a methodology based on CFD simulations is setup to identify these parameters by exciting the flow through outlet boundary condition. A simplified test case is considered to assess if 1D cavitation model parameters can be identified from CFD simulations. It is shown that a low wave speed and a second viscosity due to the cavitating flow can be identified.
Investigation the flushing flow of liquid methane in Laval nozzle
NASA Astrophysics Data System (ADS)
Snigerev, B. A.; Tukmakov, A. L.; Tonkonog, V. G.
2016-06-01
Turbulent flushing flow of methane in Laval nozzles are investigated. To describe the motion of vapor-liquid mixture are used Favre averaged over the set of equations including the equations conservation of mass, momentum, and energy for a homogeneous mixture consisting from liquid and vapour phases. Numerical flow simulation based on cavitation approach using an additional transport equation for the volume fraction of the liquid phase. The study of the expiry of boiling methane at different degrees of underheating and the back pressures in the Laval nozzle are performed.
Numerical investigation of droplet motion in rotating viscous liquid flow
NASA Astrophysics Data System (ADS)
Arkhipov, V. A.; Tkachenko, A. S.; Usanina, A. S.
2013-05-01
The results of numerical investigation of the motion of a single droplet in a twisted flow of immiscible viscous liquid are presented. The motion trajectories of a droplet depending on its size, angular velocity of liquid rotation, and the physical parameters of the liquid and droplet have been determined. The values of the Reynolds, Bond, and Weber numbers along the droplet trajectory have been calculated. The effect of the Coriolis forces on the trajectory, velocity, and acceleration of the droplet in flow have been analyzed. The effect of the acceleration components of the droplet on the parameters of its motion is estimated. The numerical results are compared with experimental data.
Supersonic Air Flow due to Solid-Liquid Impact
NASA Astrophysics Data System (ADS)
Gekle, Stephan; Peters, Ivo R.; Gordillo, José Manuel; van der Meer, Devaraj; Lohse, Detlef
2010-01-01
A solid object impacting on liquid creates a liquid jet due to the collapse of the impact cavity. Using visualization experiments with smoke particles and multiscale simulations, we show that in addition, a high-speed air jet is pushed out of the cavity. Despite an impact velocity of only 1m/s, this air jet attains supersonic speeds already when the cavity is slightly larger than 1 mm in diameter. The structure of the air flow closely resembles that of compressible flow through a nozzle—with the key difference that here the “nozzle” is a liquid cavity shrinking rapidly in time.
NASA Astrophysics Data System (ADS)
Le Voci, Giuseppe; Davies, Rhodri; Goes, Saskia; Kramer, Stephan; Wilson, Cian
2014-05-01
Arc volcanism at subduction zones is likely regulated by the mantle wedge's flow regime and thermal structure and, hence, numerous studies have attempted to quantify the principal controls on mantle wedge conditions. Here, we build on these previous studies by undertaking the first systematic 2-D and 3-D numerical investigation, across a wide parameter-space, into how hydration and thermal buoyancy influence the wedge's flow regime and associated thermal structure, above a kinematically driven subducting plate. We find that small-scale convection (SSC), resulting from Rayleigh-Taylor instabilities, or drips, off the base of the overriding lithosphere, is a typical occurrence, if: (i) viscosities are < 5×1018 Pa s; and (ii) hydrous weakening of wedge rheology extends at least 100-150 km from the trench. In 2-D models, instabilities generally take the form of 'drips'. Although along-strike averages of wedge velocities and temperature in 3-D structure are consistent with those in 2-D, fluctuations are larger in 3-D. Furthermore, in 3-D, two separate, but interacting, longitudinal Richter roll systems form (with their axes aligned perpendicular to the trench), the first below the arc region and the second below the back-arc region. These instabilities result in transient and spatial temperature fluctuations of 100-150K, which are sufficient to influence melting, the stability of hydrous minerals and the dehydration of crustal material. Furthermore, they are efficient at eroding the overriding lithosphere, particularly in 3-D and, thus, provide a means to explain observations of high heat flow and thin back-arc lithosphere at many subduction zones, if back-arc mantle is hydrated.
A comparison is made of the predictions of the Complex Terrain Dispersion Model (CTDM) with wind-tunnel observations of flow and diffusion in a simulated neutral atmospheric boundary layer over two- and three-dimensional hills. The measure used to evaluate the ability of the mode...
NASA Astrophysics Data System (ADS)
Zhao, Dongmiao; Tang, Jun; Wu, Xiuguang; Lin, Changning; Liu, Lijun; Chen, Jian
2016-05-01
A 2D vertical (2DV) numerical model, without σ-coordinate transformation in the vertical direction, is developed for the simulation of fl ow and sediment transport in open channels. In the model, time-averaged Reynolds equations are closed by the k-ɛ nonlinear turbulence model. The modifi ed Youngs-VOF method is introduced to capture free surface dynamics, and the free surface slope is simulated using the ELVIRA method. Based on the power-law scheme, the k-ɛ model and the suspended-load transport model are solved numerically with an implicit scheme applied in the vertical plane and an explicit scheme applied in the horizontal plane. Bedload transport is modeled using the Euler-WENO scheme, and the grid-closing skill is adopted to deal with the moving channel bed boundary. Verifi cation of the model using laboratory data shows that the model is able to adequately simulate fl ow and sediment transport in open channels, and is a good starting point for the study of sediment transport dynamics in strong nonlinear fl ow scenarios.
Schaffranek, Raymond W.
2004-01-01
A numerical model for simulation of surface-water integrated flow and transport in two (horizontal-space) dimensions is documented. The model solves vertically integrated forms of the equations of mass and momentum conservation and solute transport equations for heat, salt, and constituent fluxes. An equation of state for salt balance directly couples solution of the hydrodynamic and transport equations to account for the horizontal density gradient effects of salt concentrations on flow. The model can be used to simulate the hydrodynamics, transport, and water quality of well-mixed bodies of water, such as estuaries, coastal seas, harbors, lakes, rivers, and inland waterways. The finite-difference model can be applied to geographical areas bounded by any combination of closed land or open water boundaries. The simulation program accounts for sources of internal discharges (such as tributary rivers or hydraulic outfalls), tidal flats, islands, dams, and movable flow barriers or sluices. Water-quality computations can treat reactive and (or) conservative constituents simultaneously. Input requirements include bathymetric and topographic data defining land-surface elevations, time-varying water level or flow conditions at open boundaries, and hydraulic coefficients. Optional input includes the geometry of hydraulic barriers and constituent concentrations at open boundaries. Time-dependent water level, flow, and constituent-concentration data are required for model calibration and verification. Model output consists of printed reports and digital files of numerical results in forms suitable for postprocessing by graphical software programs and (or) scientific visualization packages. The model is compatible with most mainframe, workstation, mini- and micro-computer operating systems and FORTRAN compilers. This report defines the mathematical formulation and computational features of the model, explains the solution technique and related model constraints, describes the
NASA Astrophysics Data System (ADS)
Krzemianowski, Z.; Puzyrewski, R.
2014-08-01
The paper presents the main parameters of the flow field behind the guide vane cascade designed by means of 2D inverse problem and following check by means of 3D commercial program ANSYS/Fluent applied for a direct problem. This approach of using different models reflects the contemporary design procedure for non-standardized turbomachinery stage. Depending on the model, the set of conservation equation to be solved differs, although the physical background remains the same. The example of computations for guide vane cascade for a low head hydraulic turbine is presented.
Multiphase flow of miscible liquids: jets and drops
NASA Astrophysics Data System (ADS)
Walker, Travis W.; Logia, Alison N.; Fuller, Gerald G.
2015-05-01
Drops and jets of liquids that are miscible with the surrounding bulk liquid are present in many processes from cleaning surfaces with the aid of liquid soaps to the creation of biocompatible implants for drug delivery. Although the interactions of immiscible drops and jets show similarities to miscible systems, the small, transient interfacial tension associated with miscible systems create distinct outcomes such as intricate droplet shapes and breakup resistant jets. Experiments have been conducted to understand several basic multiphase flow problems involving miscible liquids. Using high-speed imaging of the morphological evolution of the flows, we have been able to show that these processes are controlled by interfacial tensions. Further multiphase flows include investigating miscible jets, which allow the creation of fibers from inelastic materials that are otherwise difficult to process due to capillary breakup. This work shows that stabilization from the diminishing interfacial tensions of the miscible jets allows various elongated morphologies to be formed.
Drop coalescence and liquid flow in a single Plateau border.
Cohen, Alexandre; Fraysse, Nathalie; Raufaste, Christophe
2015-05-01
We report a comprehensive study of the flow of liquid triggered by injecting a droplet into a liquid foam microchannel, also called a Plateau border. This drop-injected experiment reveals an intricate dynamics for the liquid redistribution, with two contrasting regimes observed, ruled either by inertia or viscosity. We devoted a previous study [A. Cohen et al., Phys. Rev. Lett. 112, 218303 (2014)] to the inertial imbibition regime, unexpected at such small length scales. Here we report other features of interest of the drop-injected experiment, related to the coalescence of the droplet with the liquid microchannel, to both the inertial and viscous regimes, and to the occurrence of liquid flow through the soap films as well as effects of the interfacial rheology. The transition between the two regimes is investigated and qualitatively accounted for. The relevance of our results to liquid foam drainage is tackled by considering the flow of liquid at the nodes of the network of interconnected microchannels. Extensions of our study to liquid foams are discussed. PMID:26066250
Drop coalescence and liquid flow in a single Plateau border
NASA Astrophysics Data System (ADS)
Cohen, Alexandre; Fraysse, Nathalie; Raufaste, Christophe
2015-05-01
We report a comprehensive study of the flow of liquid triggered by injecting a droplet into a liquid foam microchannel, also called a Plateau border. This drop-injected experiment reveals an intricate dynamics for the liquid redistribution, with two contrasting regimes observed, ruled either by inertia or viscosity. We devoted a previous study [A. Cohen et al., Phys. Rev. Lett. 112, 218303 (2014), 10.1103/PhysRevLett.112.218303] to the inertial imbibition regime, unexpected at such small length scales. Here we report other features of interest of the drop-injected experiment, related to the coalescence of the droplet with the liquid microchannel, to both the inertial and viscous regimes, and to the occurrence of liquid flow through the soap films as well as effects of the interfacial rheology. The transition between the two regimes is investigated and qualitatively accounted for. The relevance of our results to liquid foam drainage is tackled by considering the flow of liquid at the nodes of the network of interconnected microchannels. Extensions of our study to liquid foams are discussed.
Contactless Inductive Bubble Detection in a Liquid Metal Flow.
Gundrum, Thomas; Büttner, Philipp; Dekdouk, Bachir; Peyton, Anthony; Wondrak, Thomas; Galindo, Vladimir; Eckert, Sven
2016-01-01
The detection of bubbles in liquid metals is important for many technical applications. The opaqueness and the high temperature of liquid metals set high demands on the measurement system. The high electrical conductivity of the liquid metal can be exploited for contactless methods based on electromagnetic induction. We will present a measurement system which consists of one excitation coil and a pickup coil system on the opposite sides of the pipe. With this sensor we were able to detect bubbles in a sodium flow inside a stainless steel pipe and bubbles in a column filled with a liquid Gallium alloy. PMID:26751444
Contactless Inductive Bubble Detection in a Liquid Metal Flow
Gundrum, Thomas; Büttner, Philipp; Dekdouk, Bachir; Peyton, Anthony; Wondrak, Thomas; Galindo, Vladimir; Eckert, Sven
2016-01-01
The detection of bubbles in liquid metals is important for many technical applications. The opaqueness and the high temperature of liquid metals set high demands on the measurement system. The high electrical conductivity of the liquid metal can be exploited for contactless methods based on electromagnetic induction. We will present a measurement system which consists of one excitation coil and a pickup coil system on the opposite sides of the pipe. With this sensor we were able to detect bubbles in a sodium flow inside a stainless steel pipe and bubbles in a column filled with a liquid Gallium alloy. PMID:26751444
Emittance Measurements for a Thin Liquid Sheet Flow
NASA Technical Reports Server (NTRS)
Englehart, Amy N.; McConley, Marc W.; Chubb, Donald L.
1996-01-01
The Liquid Sheet Radiator (LSR) is an external flow radiator that uses a triangular-shaped flowing liquid sheet as the radiating surface. It has potentially much lower mass than solid wall radiators such as pumped loop and heat pipe radiators, along with being nearly immune to micrometeoroid penetration. The LSR has an added advantage of simplicity. Surface tension causes a thin (100-300 microns) liquid sheet to coalesce to a point, causing the sheet flow to have a triangular shape. Such a triangular sheet is desirable since it allows for simple collection of the flow at a single point. A major problem for all external flow radiators is the requirement that the working fluid be of very low (approx. 10(sup -8) torr) vapor pressure to keep evaporative losses low. As a result, working fluids are limited to certain oils (such as used in diffusion pumps) for low temperatures (300-400 K) and liquid metals for higher temperatures. Previous research on the LSR has been directed at understanding the fluid mechanics of thin sheet flows and assessing the stability of such flows, especially with regard to the formation of holes in the sheet. Taylor studied extensively the stability of thin liquid sheets both theoretically and experimentally. He showed that thin sheets in a vacuum are stable. The latest research has been directed at determining the emittance of thin sheet flows. The emittance was calculated from spectral transmittance data for the Dow Corning 705 silicone oil. By experimentally setting up a sheet flow, the emittance was also determined as a function of measurable quantities, most importantly, the temperature drop between the top of the sheet and the temperature at the coalescence point of the sheet. Temperature fluctuations upstream of the liquid sheet were a potential problem in the analysis and were investigated.
NASA Technical Reports Server (NTRS)
Thompson David S.; Soni, Bharat K.
2001-01-01
An integrated geometry/grid/simulation software package, ICEG2D, is being developed to automate computational fluid dynamics (CFD) simulations for single- and multi-element airfoils with ice accretions. The current version, ICEG213 (v2.0), was designed to automatically perform four primary functions: (1) generate a grid-ready surface definition based on the geometrical characteristics of the iced airfoil surface, (2) generate high-quality structured and generalized grids starting from a defined surface definition, (3) generate the input and restart files needed to run the structured grid CFD solver NPARC or the generalized grid CFD solver HYBFL2D, and (4) using the flow solutions, generate solution-adaptive grids. ICEG2D (v2.0) can be operated in either a batch mode using a script file or in an interactive mode by entering directives from a command line within a Unix shell. This report summarizes activities completed in the first two years of a three-year research and development program to address automation issues related to CFD simulations for airfoils with ice accretions. As well as describing the technology employed in the software, this document serves as a users manual providing installation and operating instructions. An evaluation of the software is also presented.
Vanrobaeys, Frank; Van Coster, Rudy; Dhondt, Goedele; Devreese, Bart; Van Beeumen, Jozef
2005-01-01
The myelin sheath is an electrically insulating layer that consists of lipids and proteins. It plays a key role in the functioning of the nervous system by allowing fast saltatory conduction of nerve pulses. Profiling of the proteins present in myelin is an indispensable prerequisite to better understand the molecular aspects of this dynamic, functionally active membrane. Two types of protein, the myelin basic protein and the proteolipid protein, account for nearly 85% of the protein content in myelin. Identification and characterization of the other "minor" proteins is, in this respect, a real challenge. In the present work, two proteomic strategies were applied in order to study the protein composition of myelin from the murine central nervous system. First, the protein mixture was separated by 2D-gel electrophoresis and, after spot excision and in-gel digestion, samples were analyzed by mass spectrometry. Via this approach, we identified 57 protein spots, corresponding to 38 unique proteins. Alternatively, the myelin sample was digested by trypsin and the resulting peptide mixture was further analyzed by off-line 2D-liquid chromatography. After the second-dimension separation (nanoLC), the peptides were spotted "on-line" onto a MALDI target and analyzed by MALDI TOF-TOF mass spectrometry. We identified 812 peptides by MALDI MS/MS, representing 93 proteins. Membrane proteins, low abundant proteins, and highly basic proteins were all represented in this shotgun proteomic approach. By combining the results of both approaches, we can present a comprehensive proteomic map of myelin, comprising a total of 103 protein identifications, which is of utmost importance for the molecular understanding of white matter and its disorders. PMID:16335977
NASA Technical Reports Server (NTRS)
Olsen, George C.; Nowak, Robert J.; Holden, Michael S.; Baker, N. R.
1990-01-01
An experimental program was conducted to establish some design parameters important to a supersonic film cooling system in a scramjet engine. A simple non-combusting two-dimensional flow configuration was used to isolate the film cooling phenomena. Parameters investigated include coolant delivery pressure, slot height and lip thickness, and incident shock location and strength. Design guidelines for use in engineering and trade studies are presented.
2D dual permeability modeling of flow and transport in a two-scale structured lignitic mine soil
NASA Astrophysics Data System (ADS)
Dusek, J.; Gerke, H. H.; Vogel, T.; Maurer, T.; Buczko, U.
2009-04-01
Two-dimensional single- and dual-permeability simulations are used to analyze water and solute fluxes in heterogeneous lignitic mine soil at a forest-reclaimed mine spoil heap. The soil heterogeneity on this experimental site "Bärenbrücker Höhe" resulted from inclined dumping structures and sediment mixtures that consist of sand with lignitic dust and embedded lignitic fragments. Observations on undisturbed field suction-cell lysimeters including tracer experiments revealed funneling-type preferential flow with lateral water and bromide movement along inclined sediment structures. The spatial distribution of soil structures and fragment distributions was acquired by a digital camera and identified by a supervised classification of the digital profile image. First, a classical single-domain modeling approach was used, with spatially variable scaling factors inferred from image analyses. In the next step, a two-continuum scenario was constructed to examine additional effects of nonequilibrium on the flow regime. The scaling factors used for the preferential flow domain are here obtained from the gradient of the grayscale images. So far, the single domain scenarios failed to predict the bromide leaching patterns although water effluent could be described. Dual-permeability model allows the incorporation of structural effects and can be used as a tool to further testing other approaches that account for structure effects. The numerical study suggests that additional experiments are required to obtain better understanding of the highly complex transport processes on this experimental site.
Lappala, E.G.; Healy, R.W.; Weeks, E.P.
1987-01-01
This report documents FORTRAN computer code for solving problems involving variably saturated single-phase flow in porous media. The flow equation is written with total hydraulic potential as the dependent variable, which allows straightforward treatment of both saturated and unsaturated conditions. The spatial derivatives in the flow equation are approximated by central differences, and time derivatives are approximated either by a fully implicit backward or by a centered-difference scheme. Nonlinear conductance and storage terms may be linearized using either an explicit method or an implicit Newton-Raphson method. Relative hydraulic conductivity is evaluated at cell boundaries by using either full upstream weighting, the arithmetic mean, or the geometric mean of values from adjacent cells. Nonlinear boundary conditions treated by the code include infiltration, evaporation, and seepage faces. Extraction by plant roots that is caused by atmospheric demand is included as a nonlinear sink term. These nonlinear boundary and sink terms are linearized implicitly. The code has been verified for several one-dimensional linear problems for which analytical solutions exist and against two nonlinear problems that have been simulated with other numerical models. A complete listing of data-entry requirements and data entry and results for three example problems are provided. (USGS)
Flow patterns in free liquid film caused by thermocapillary effect
NASA Astrophysics Data System (ADS)
Ueno, Ichiro; Fei, Linhao; Kowata, Yosuke; Kaneko, Toshihiro; Pettit, Donald
2015-11-01
The basic flow patterns realized in a thin free liquid film driven by the thermocapillary effect are focused. Spetial attention is paied to the effect of the volume ratio of the liquid film to the hole sustaining the film on the flow patterns. We prepare a thin liquid film of less than 0 . 5 mm in thickness in order to stably realize the film under normal gravity. Liquid has in general negative temperature coefficient of it surface tension; that is, the fluid is driven to the colder to hotter regions by the non-uniform surface-tension distribution. In the case of thin free liquid film, however, it is found that a unique flow pattern is induced. One of the present authors, DRP, carried out a series of experiments under microgravity condition in the International Space Station (ISS) in 2003. He prepared a ring made of metal, and formed a thin film of water inside the ring. Once he added a non-uniform temperature distribution to the film by placing a heated iron at one end of the ring, a net flow toward the heated iron was realized. In order to understand flow patterns, we focus on the flow structures of the thermocapillary convection in a cross section normal to the end walls as well as the surface temperature distributions.
A study of vapor-liquid flow in porous media
Satik, Cengiz; Yortsos, Yanis C.
1994-01-20
We study the heat transfer-driven liquid-to-vapor phase change in single-component systems in porous media by using pore network models and flow visualization experiments. Experiments using glass micromodels were conducted. The flow visualization allowed us to define the rules for the numerical pore network model. A numerical pore network model is developed for vapor-liquid displacement where fluid flow, heat transfer and capillarity are included at the pore level. We examine the growth process at two different boundary conditions.
Thermohydrodynamic analysis of cryogenic liquid turbulent flow fluid film bearings
NASA Technical Reports Server (NTRS)
Andres, Luis San
1993-01-01
A thermohydrodynamic analysis is presented and a computer code developed for prediction of the static and dynamic force response of hydrostatic journal bearings (HJB's), annular seals or damper bearing seals, and fixed arc pad bearings for cryogenic liquid applications. The study includes the most important flow characteristics found in cryogenic fluid film bearings such as flow turbulence, fluid inertia, liquid compressibility and thermal effects. The analysis and computational model devised allow the determination of the flow field in cryogenic fluid film bearings along with the dynamic force coefficients for rotor-bearing stability analysis.
Liquid phase oxidation chemistry in continuous-flow microreactors.
Gemoets, Hannes P L; Su, Yuanhai; Shang, Minjing; Hessel, Volker; Luque, Rafael; Noël, Timothy
2016-01-01
Continuous-flow liquid phase oxidation chemistry in microreactors receives a lot of attention as the reactor provides enhanced heat and mass transfer characteristics, safe use of hazardous oxidants, high interfacial areas, and scale-up potential. In this review, an up-to-date overview of both technological and chemical aspects of liquid phase oxidation chemistry in continuous-flow microreactors is given. A description of mass and heat transfer phenomena is provided and fundamental principles are deduced which can be used to make a judicious choice for a suitable reactor. In addition, the safety aspects of continuous-flow technology are discussed. Next, oxidation chemistry in flow is discussed, including the use of oxygen, hydrogen peroxide, ozone and other oxidants in flow. Finally, the scale-up potential for continuous-flow reactors is described. PMID:26203551
Flow induced charging of liquids in reduced gravity
Pettit, D.R.
1996-02-01
Microgravity experiments on free fluid surfaces of large length scale could be subject to experimental artifact from flow induced charging. Under conditions favorable for flow induced charging, flowing liquids develop a static electrical charge which manifests itself as a force whose magnitude approaches that of surface tension force. Favorable conditions are: a non-conducting liquid, a small diameter non-conducting flow passage, a large flow volume, and a small separation distance between the fluid and another object. We present a method for calculating the magnitude of flow induced charging and scaling arguments so that potential problems can be determined and dealt with at the experimental design phase. A dimensionless ratio of charge force to surface tension force we call the Hula Number should be less than 0.5 to prevent artifact or unwanted fluid motion.
NASA Astrophysics Data System (ADS)
Berdagué, Philippe; Lesot, Philippe; Jacob, Jérémy; Terwilliger, Valery J.; Le Milbeau, Claude
2016-01-01
The hydrogen isotopic composition (δD or (D/H) value) of molecular biomarkers preserved in sedimentary archives is increasingly used to provide clues about the evolution of past climatic conditions. The rationale is that intact biomarkers retain isotopic information related to the climatic conditions that prevailed at the time of their synthesis. Some of these biomarkers may be degraded during diagenesis, however. The extent to which these degradations alter the original δD value of the source biomarker is presently debated and the capacity to resolve this question by determination of compound-specific δD values alone is limited. The "bulk" or "global" δD value of any molecule is in fact a composite of δD values at each site within this molecule (δDi or (D/H)i with i = number of hydrogen/deuterium atoms in the considered molecule). Determination of this site-specific δDi value in biomarkers could not only yield outstanding paleoenvironmental information but also help forecast the impacts of diagenesis and define essential steps in biosynthetic pathways. This task is analytically challenging. Here, we examined the capabilities of natural abundance deuterium 2D-NMR (NAD 2D-NMR) using homopolypeptide liquid crystals as an NMR solvent to: (i) analyze the NAD spectra of biomakers; (ii) determine the site-specific distribution of hydrogen in the nine methyl groups (δDMei with i = 23-31) of miliacin, a pentacyclic triterpene of the amyrin family and key biomarker for broomcorn millet in sedimentary archives. Relative (D/H)Mei values were established by anisotropic NAD 2D-NMR. Then absolute δDMei values were obtained by determining δDMei value of the methoxy group of miliacin using two independent approaches: isotropic NAD NMR (SNIF-NMR™) and GC-irMS. The resulting isotope profile for miliacin shows, for the first time, large variations in δDMei values that can directly be explained by biosynthetic processes. This approach has also the potential to permit
NASA Astrophysics Data System (ADS)
Morgan, J. P.; de Monserrat, A.; Hall, R.; Taramon, J. M.; Perez-Gussinye, M.
2015-12-01
This work focuses on improving current 2D numerical approaches to modeling the boundary conditions associated with computing accurate deformation and melting associated with continental rifting. Recent models primarily use far-field boundary conditions that have been used for decades with little assessment of their effects on asthenospheric flow beneath the rifting region. All are clearly extremely oversimplified — Huismans and Buiter assume there is no vertical flow into the rifting region, with the asthenosphere flowing uniformly into the rifting region from the sides beneath lithosphere moving in the opposing direction, Armitage et al. and van Wijk use divergent velocities on the upper boundary to impose break-up within a Cartesian box, while other studies generally assume there is uniform horizontal flow away from the center of rifting, with uniform vertical flow replenishing the material pulled out of the sides of the computational region. All are likely to significantly shape the pattern of asthenospheric flow beneath the stretching lithosphere that is associated with pressure-release melting and rift volcanism. Thus while ALL may lead to similar predictions of the effects of crustal stretching and thinning, NONE may lead to accurate determination of the the asthenospheric flow and melting associated with lithospheric stretching and breakup. Here we discuss a suite of numerical experiments that compare these choices to likely more realistic boundary condition choices like the analytical solution for flow associated with two diverging plates stretching over a finite-width region, and a high-resolution 2-D region embedded within a cylindrical annulus 'whole mantle cross-section' at 5% extra numerical problem size. Our initial results imply that the choice of far-field boundary conditions does indeed significantly influence predicted melting distributions and melt volumes associated with continental breakup. For calculations including asthenospheric melting
Liquid rocket engine axial-flow turbopumps
NASA Technical Reports Server (NTRS)
Scheer, D. D.; Huppert, M. C.; Viteri, F.; Farquhar, J.; Keller, R. B., Jr. (Editor)
1978-01-01
The axial pump is considered in terms of the total turbopump assembly. Stage hydrodynamic design, pump rotor assembly, pump materials for liquid hydrogen applications, and safety factors as utilized in state of the art pumps are among the topics discussed. Axial pump applications are included.
NASA Astrophysics Data System (ADS)
Chaudhuri, A.; Sekhar, M.; Descloitres, M.; Godderis, Y.; Ruiz, L.; Braun, J. J.
2013-11-01
Stochastic modelling is a useful way of simulating complex hard-rock aquifers as hydrological properties (permeability, porosity etc.) can be described using random variables with known statistics. However, very few studies have assessed the influence of topological uncertainty (i.e. the variability of thickness of conductive zones in the aquifer), probably because it is not easy to retrieve accurate statistics of the aquifer geometry, especially in hard rock context. In this paper, we assessed the potential of using geophysical surveys to describe the geometry of a hard rock-aquifer in a stochastic modelling framework. The study site was a small experimental watershed in South India, where the aquifer consisted of a clayey to loamy-sandy zone (regolith) underlain by a conductive fissured rock layer (protolith) and the unweathered gneiss (bedrock) at the bottom. The spatial variability of the thickness of the regolith and fissured layers was estimated by electrical resistivity tomography (ERT) profiles, which were performed along a few cross sections in the watershed. For stochastic analysis using Monte Carlo simulation, the generated random layer thickness was made conditional to the available data from the geophysics. In order to simulate steady state flow in the irregular domain with variable geometry, we used an isoparametric finite element method to discretize the flow equation over an unstructured grid with irregular hexahedral elements. The results indicated that the spatial variability of the layer thickness had a significant effect on reducing the simulated effective steady seepage flux and that using the conditional simulations reduced the uncertainty of the simulated seepage flux. As a conclusion, combining information on the aquifer geometry obtained from geophysical surveys with stochastic modelling is a promising methodology to improve the simulation of groundwater flow in complex hard-rock aquifers.
NASA Technical Reports Server (NTRS)
Seasholtz, Richard G.
1995-01-01
A Rayleigh scattering diagnostic for high speed flows is described for the simultaneous, instantaneous measurement of gas temperature and velocity at a number (up to about one hundred) of locations in a plane illuminated by an injection-seeded, frequency doubled Nd:YAG laser. Molecular Rayleigh scattered light is collected and passed through a planar mirror Fabry-Perot interferometer. The resulting image is analyzed to determine the gas temperature and bulk velocity at each of the regions. The Cramer Rao lower bound for measurement uncertainty is calculated. Experimental data is presented for a free jet and for preliminary measurements in the Lewis 4 inch by 10 inch supersonic wind tunnel.
Instability due to interfacial tension in parallel liquid-liquid flow
NASA Astrophysics Data System (ADS)
Rodriguez, Oscar M. H.
2016-06-01
The frequent occurrence of multiphase flows in pipes has motivated a great research interest over the last decades. The particular case of liquid-liquid flow is commonly encountered in the petroleum industry, where a number of applications involve oil-water flow such as crude oil production in directional wells. However, it has not received the same attention when compared to gas-liquid flow. In addition, most of the available information has to do with flow in pipes. When it comes to flows in annular ducts the data are scanty. A general transition criterion has been recently proposed in order to obtain the stratified and core-annular flow-pattern transition boundaries in viscous oil-water flow. The proposed criterion was based on an one-dimensional two-fluid model of liquid-liquid two-phase flow. A stability analysis was carried out and interfacial tension is considered. A new destabilizing term arises, which is a function of the cross-section curvature of the interface. It is well accepted that interfacial tension favors the stable condition. However, the analysis of the new interfacial-tension term shows that it can actually destabilize the basic flow pattern, playing an important role in regions of extreme volumetric fractions. Such an interesting effect seems to be more pronounced in flows of viscous fluids and in annular-duct flow. The effect of interfacial tension is explored and the advantages of using a more complete model are discussed and illustrated through comparisons with experimental data from the literature. The evaluation of the effects of fluid viscosity and interfacial tension allows the correction and enhancement of transition models based essentially on data of pipe flow of low viscosity fluids.
NASA Astrophysics Data System (ADS)
Eckert, Dominik; Kürzinger, Petra; Bauer, Robert; Griebler, Christian; Cirpka, Olaf A.
2015-01-01
Biodegradation in contaminated aquifers has been shown to be most pronounced at the fringe of contaminant plumes, where mixing of contaminated water and ambient groundwater, containing dissolved electron acceptors, stimulates microbial activity. While physical mixing of contaminant and electron acceptor by transverse dispersion has been shown to be the major bottleneck for biodegradation in steady-state plumes, so far little is known on the effect of flow and transport dynamics (caused, e.g., by a seasonally fluctuating groundwater table) on biodegradation in these systems. Towards this end we performed experiments in quasi-two-dimensional flow-through microcosms on aerobic toluene degradation by Pseudomonas putida F1. Plume dynamics were simulated by vertical alteration of the toluene plume position and experimental results were analyzed by reactive-transport modeling. We found that, even after disappearance of the toluene plume for two weeks, the majority of microorganisms stayed attached to the sediment and regained their full biodegradation potential within two days after reappearance of the toluene plume. Our results underline that besides microbial growth, also maintenance and dormancy are important processes that affect biodegradation performance under transient environmental conditions and therefore deserve increased consideration in future reactive-transport modeling.
NASA Astrophysics Data System (ADS)
Caviedes-Voullième, Daniel; Juez, Carmelo; Murillo, Javier; García-Navarro, Pilar
2014-12-01
Avalanches, debris flows and other types of gravity-driven granular flows are a common hazard in mountainous regions. These regions often have human settlements in the lower parts of valleys, with human structures dangerously exposed to the destructive effects of these geophysical flows. Therefore a scientific effort has been made to understand, model and simulate geophysical granular flows. In order for computer models and simulations to be of predictive value they need to be validated under controlled, yet nature-like conditions. This work presents an experimental study of granular flow over a simplified mountain slope and valley topography. The experimental facility has a rough bed with very high slope at the upstream end and adverse slope on the downstream end, following a parabolic profile. Obstacles are present in the lower regions. Transient measurements of the moving granular surfaces were taken with a consumer-grade RGB-D sensor, providing transient 2D elevation fields around the obstacles. Three experimental configurations were tested, with semispheres of different diameters and a square dike obstacle. The experimental results are very consistent and repeatable. The quantitative, transient and two-dimensional data for all three experiments constitute excellent benchmarking tests for computational models, such as the one presented in a companion paper.
Gao, Hang; Bijnens, Nathalie; Coisne, Damien; Lugiez, Mathieu; Rutten, Marcel; D'hooge, Jan
2015-01-01
Despite the availability of multiple ultrasound approaches to left ventricular (LV) flow characterization in two dimensions, this technique remains in its childhood and further developments seem warranted. This article describes a new methodology for tracking the 2-D LV flow field based on ultrasound data. Hereto, a standard speckle tracking algorithm was modified by using a dynamic kernel embedding Navier-Stokes-based regularization in an iterative manner. The performance of the proposed approach was first quantified in synthetic ultrasound data based on a computational fluid dynamics model of LV flow. Next, an experimental flow phantom setup mimicking the normal human heart was used for experimental validation by employing simultaneous optical particle image velocimetry as a standard reference technique. Finally, the applicability of the approach was tested in a clinical setting. On the basis of the simulated data, pointwise evaluation of the estimated velocity vectors correlated well (mean r = 0.84) with the computational fluid dynamics measurement. During the filling period of the left ventricle, the properties of the main vortex obtained from the proposed method were also measured, and their correlations with the reference measurement were also calculated (radius, r = 0.96; circulation, r = 0.85; weighted center, r = 0.81). In vitro results at 60 bpm during one cardiac cycle confirmed that the algorithm properly measures typical characteristics of the vortex (radius, r = 0.60; circulation, r = 0.81; weighted center, r = 0.92). Preliminary qualitative results on clinical data revealed physiologic flow fields. PMID:25438850
DYNAMIC MODELING STRATEGY FOR FLOW REGIME TRANSITION IN GAS-LIQUID TWO-PHASE FLOWS
X. Wang; X. Sun; H. Zhao
2011-09-01
In modeling gas-liquid two-phase flows, the concept of flow regime has been used to characterize the global interfacial structure of the flows. Nearly all constitutive relations that provide closures to the interfacial transfers in two-phase flow models, such as the two-fluid model, are often flow regime dependent. Currently, the determination of the flow regimes is primarily based on flow regime maps or transition criteria, which are developed for steady-state, fully-developed flows and widely applied in nuclear reactor system safety analysis codes, such as RELAP5. As two-phase flows are observed to be dynamic in nature (fully-developed two-phase flows generally do not exist in real applications), it is of importance to model the flow regime transition dynamically for more accurate predictions of two-phase flows. The present work aims to develop a dynamic modeling strategy for determining flow regimes in gas-liquid two-phase flows through the introduction of interfacial area transport equations (IATEs) within the framework of a two-fluid model. The IATE is a transport equation that models the interfacial area concentration by considering the creation and destruction of the interfacial area, such as the fluid particle (bubble or liquid droplet) disintegration, boiling and evaporation; and fluid particle coalescence and condensation, respectively. For the flow regimes beyond bubbly flows, a two-group IATE has been proposed, in which bubbles are divided into two groups based on their size and shape (which are correlated), namely small bubbles and large bubbles. A preliminary approach to dynamically identifying the flow regimes is provided, in which discriminators are based on the predicted information, such as the void fraction and interfacial area concentration of small bubble and large bubble groups. This method is expected to be applied to computer codes to improve their predictive capabilities of gas-liquid two-phase flows, in particular for the applications in
Dual-plane ultrasound flow measurements in liquid metals
NASA Astrophysics Data System (ADS)
Büttner, Lars; Nauber, Richard; Burger, Markus; Räbiger, Dirk; Franke, Sven; Eckert, Sven; Czarske, Jürgen
2013-05-01
An ultrasound measurement system for dual-plane, two-component flow velocity measurements especially in opaque liquids is presented. Present-day techniques for measuring local flow structures in opaque liquids disclose considerable drawbacks concerning line-wise measurement of single ultrasound probes. For studying time-varying flow patterns, conventional ultrasound techniques are either limited by time-consuming mechanical traversing or by the sequential operation of single probes. The measurement system presented within this paper employs four transducer arrays with a total of 100 single elements which allows for flow mapping without mechanical traversing. A high frame rate of several 10 Hz has been achieved due to an efficient parallelization scheme using time-division multiplexing realized by a microcontroller-based electronic switching matrix. The functionality and capability of the measurement system are demonstrated on a liquid metal flow at room temperature inside a cube driven by a rotating magnetic field (RMF). For the first time, the primary and the secondary flow have been studied in detail and simultaneously using a configuration with two crossed measurement planes. The experimental data confirm predictions made by numeric simulation. After a sudden switching on of the RMF, inertial oscillations of the secondary flow were observed by means of a time-resolved measurement with a frame rate of 3.4 Hz. The experiments demonstrate that the presented measurement system is able to investigate complex and transient flow structures in opaque liquids. Due to its ability to study the temporal evolution of local flow structures, the measurement system could provide considerable progress for fluid dynamics research, in particular for applications in the food industry or liquid metal technologies.
Patwa, Tasneem H.; Wang, Yanfei; Miller, Fred R.; Goodison, Steve; Pennathur, Subramaniam; Barder, Timothy J.; Lubman, David M.
2008-01-01
An analysis of phosphorylation changes that occur during cancer progression would provide insights into the molecular pathways responsible for a malignant phenotype. In this study we employed a novel coupling of 2D-liquid separations and protein microarray technology to reveal changes in phosphoprotein status between premalignant (AT1) and malignant (CA1a) cell lines derived from the human MCF10A breast cell lines. Intact proteins were first separated according to their isoelectric point and hydrophobicities, then arrayed on SuperAmine glass slides. Phosphoproteins were detected using the universal, inorganic phospho-sensor dye, ProQ Diamond. Using this dye, out of 140 spots that were positive for phosphorylation, a total of 85 differentially expressed spots were detected over a pH range of 7.2 to 4.0. Proteins were identified and their peptides sequenced by mass spectrometry. The strategy enabled the identification of 75 differentially expressed phosphoproteins, from which 51 phosphorylation sites in 27 unique proteins were confirmed. Interestingly, the majority of differentially expressed phosphorylated proteins observed were nuclear proteins. Three regulators of apoptosis, Bad, Bax and Acinus, were also differentially phosphorylated in the two cell lines. Further development of this strategy will facilitate an understanding of the mechanisms involved in malignancy progression and other disease-related phenotypes. PMID:19194518
NASA Astrophysics Data System (ADS)
Ganesh, Rajaraman; Charan, Harish
2016-07-01
Understanding vortical flows under external forcing in two dimensional (2D) fluids is a fundamental paradigm for structure formation in driven, dissipative systems. Considering Yukawa liquid as a prototype for strongly correlated or strongly coupled plasmas characterized by coupling strength (Γ, the ratio of average potential to kinetic energy per particle) and screening parameter (κ, ratio of mean inter-particle distance to shielding length), we address two important problems: 1. Onset of Rayleigh Benard convection cell (RBCC) in 2D Yukawa liquids subject to gravity and external temperature gradient 2. Onset of von Karman vortices in 2D Yukawa liquid under external pressure head, using large scale, first principles molecular dynamics simulations. For typical values of (Γ,κ), existence of a critical external temperature difference is demonstrated, beyond which RBCC are seen to set in. Beyond this critical external temperature difference, the strength of the maximum convective flow velocity is shown to exhibit a new, hitherto unsuspected linear relationship with external temperature difference and with a slope independent of (Γ,κ). The time taken for the transients to settle down to a steady state RBCC τ_s, is found to be maximum close to the above said critical external temperature difference and is seen to reduce with increasing external temperature difference. For the range of values of (Γ, κ) considered here, τ_s ≃ 10 000-20 000;ω^{-1}_{pd}, where ω_{pd} is dust plasma frequency. As Γ is increased to very high values, due to strong coupling effects, RBC cells are seen to be in a transient state without attaining a steady state for as long as 100 000;ω^{-1}_{pd}, even for a very high external temperature difference. In the second part, we address the existence of universal relation between Strouhal (St) and Rayleigh (Ry) numbers for Yukawa liquid using first principles based classical molecular dynamics. The flow past an obstacle is seen to indeed
Chouhan, Manil D; Mookerjee, Rajeshwar P; Bainbridge, Alan; Walker-Samuel, Simon; Davies, Nathan; Halligan, Steve; Lythgoe, Mark F; Taylor, Stuart A
2016-09-01
Purpose To validate caval subtraction two-dimensional (2D) phase-contrast magnetic resonance (MR) imaging measurements of total liver blood flow (TLBF) and hepatic arterial fraction in an animal model and evaluate consistency and reproducibility in humans. Materials and Methods Approval from the institutional ethical committee for animal care and research ethics was obtained. Fifteen Sprague-Dawley rats underwent 2D phase-contrast MR imaging of the portal vein (PV) and infrahepatic and suprahepatic inferior vena cava (IVC). TLBF and hepatic arterial flow were estimated by subtracting infrahepatic from suprahepatic IVC flow and PV flow from estimated TLBF, respectively. Direct PV transit-time ultrasonography (US) and fluorescent microsphere measurements of hepatic arterial fraction were the standards of reference. Thereafter, consistency of caval subtraction phase-contrast MR imaging-derived TLBF and hepatic arterial flow was assessed in 13 volunteers (mean age, 28.3 years ± 1.4) against directly measured phase-contrast MR imaging PV and proper hepatic arterial inflow; reproducibility was measured after 7 days. Bland-Altman analysis of agreement and coefficient of variation comparisons were undertaken. Results There was good agreement between PV flow measured with phase-contrast MR imaging and that measured with transit-time US (mean difference, -3.5 mL/min/100 g; 95% limits of agreement [LOA], ±61.3 mL/min/100 g). Hepatic arterial fraction obtained with caval subtraction agreed well with those with fluorescent microspheres (mean difference, 4.2%; 95% LOA, ±20.5%). Good consistency was demonstrated between TLBF in humans measured with caval subtraction and direct inflow phase-contrast MR imaging (mean difference, -1.3 mL/min/100 g; 95% LOA, ±23.1 mL/min/100 g). TLBF reproducibility at 7 days was similar between the two methods (95% LOA, ±31.6 mL/min/100 g vs ±29.6 mL/min/100 g). Conclusion Caval subtraction phase-contrast MR imaging is a simple and clinically
Gas-Liquid Flows and Phase Separation
NASA Technical Reports Server (NTRS)
McQuillen, John
2004-01-01
Common issues for space system designers include:Ability to Verify Performance in Normal Gravity prior to Deployment; System Stability; Phase Accumulation & Shedding; Phase Separation; Flow Distribution through Tees & Manifolds Boiling Crisis; Heat Transfer Coefficient; and Pressure Drop.The report concludes:Guidance similar to "A design that operates in a single phase is less complex than a design that has two-phase flow" is not always true considering the amount of effort spent on pressurizing, subcooling and phase separators to ensure single phase operation. While there is still much to learn about two-phase flow in reduced gravity, we have a good start. Focus now needs to be directed more towards system level problems .
Yanase, Nobuyuki; Naganawa, Hirochika; Nagano, Tetsushi; Noro, Junji
2011-01-01
A single current "emulsion flow" liquid-liquid extraction apparatus has a head with a number of holes from which micrometer-sized droplets of an aqueous phase spout into an organic phase to mix the two liquid phases. For practical use, however, a fatal problem can occur when particulate components in the aqueous phase plug the holes. In the present study, we have succeeded in solving the problem by applying a counter current-type emulsion flow extractor where micrometer-sized droplets of the organic phase are generated. PMID:21415518
Mass flow measurement of liquid cryogens using the triboelectric effect
NASA Technical Reports Server (NTRS)
Dechene, Ronald L.
1986-01-01
A cross correlator technique using triboelectric technology has been shown to be a feasible method to measure liquid flow rate for liquid nitrogen and JP4 jet fuel. This technology, invented and pioneered by Auburn International, Inc., is also expected to be suitable for use with all other insulating liquids and cryogens. The technology described is particularly well suited for cryogenic use, since the sensor is non-contacting and non-intrusive, and therefore, causes no additional pressure drop within the flow stream. Further development of the in-line sensor is required to produce a prototypical version for the test purposes under SSME fuel flow conditions. However, with the knowledge gained from this feasibility study, it is very likely that an acceptable sensor design for a full test bed evaluation could be produced.
NASA Astrophysics Data System (ADS)
Zhang, Wei; Markfort, Corey; Porté-Agel, Fernando
2014-11-01
Turbulent flows over complex surface topography have been of great interest in the atmospheric science and wind engineering communities. The geometry of the topography, surface roughness and temperature characteristics as well as the atmospheric thermal stability play important roles in determining momentum and scalar flux distribution. Studies of turbulent flow over simplified topography models, under neutrally stratified boundary-layer conditions, have provided insights into fluid dynamics. However, atmospheric thermal stability has rarely been considered in laboratory experiments, e.g., wind-tunnel experiments. Series of wind-tunnel experiments of thermally-stratified boundary-layer flow over a surface-mounted 2-D block, in a well-controlled boundary-layer wind tunnel, will be presented. Measurements using high-resolution PIV, x-wire/cold-wire anemometry and surface heat flux sensors were conducted to quantify the turbulent flow properties, including the size of the recirculation zone, coherent vortex structures and the subsequent boundary layer recovery. Results will be shown to address thermal stability effects on momentum and scalar flux distribution in the wake, as well as dominant mechanism of turbulent kinetic energy generation and consumption. The authors gratefully acknowledge funding from the Swiss National Foundation (Grant 200021-132122), the National Science Foundation (Grant ATM-0854766) and NASA (Grant NNG06GE256).
About the statistical description of gas-liquid flows
Sanz, D.; Guido-Lavalle, G.; Carrica, P.
1995-09-01
Elements of the probabilistic geometry are used to derive the bubble coalescence term of the statistical description of gas liquid flows. It is shown that the Boltzmann`s hypothesis, that leads to the kinetic theory of dilute gases, is not appropriate for this kind of flows. The resulting integro-differential transport equation is numerically integrated to study the flow development in slender bubble columns. The solution remarkably predicts the transition from bubbly to slug flow pattern. Moreover, a bubbly bimodal size distribution is predicted, which has already been observed experimentally.
Steering liquid metal flow in microchannels using low voltages.
Tang, Shi-Yang; Lin, Yiliang; Joshipura, Ishan D; Khoshmanesh, Khashayar; Dickey, Michael D
2015-10-01
Liquid metals based on gallium, such as eutectic gallium indium (EGaIn) and Galinstan, have been integrated as static components in microfluidic systems for a wide range of applications including soft electrodes, pumps, and stretchable electronics. However, there is also a possibility to continuously pump liquid metal into microchannels to create shape reconfigurable metallic structures. Enabling this concept necessitates a simple method to control dynamically the path the metal takes through branched microchannels with multiple outlets. This paper demonstrates a novel method for controlling the directional flow of EGaIn liquid metal in complex microfluidic networks by simply applying a low voltage to the metal. According to the polarity of the voltage applied between the inlet and an outlet, two distinct mechanisms can occur. The voltage can lower the interfacial tension of the metal via electrocapillarity to facilitate the flow of the metal towards outlets containing counter electrodes. Alternatively, the voltage can drive surface oxidation of the metal to form a mechanical impediment that redirects the movement of the metal towards alternative pathways. Thus, the method can be employed like a 'valve' to direct the pathway chosen by the metal without mechanical moving parts. The paper elucidates the operating mechanisms of this valving system and demonstrates proof-of-concept control over the flow of liquid metal towards single or multiple directions simultaneously. This method provides a simple route to direct the flow of liquid metal for applications in microfluidics, optics, electronics, and microelectromechanical systems. PMID:26279150
Impact of a single drop on a flowing liquid film.
Gao, Xuan; Li, Ri
2015-11-01
The impact of a single liquid drop on a flowing liquid film is experimentally and theoretically studied. The drop impact produces a crownlike rising liquid sheet, which radially expands. Small droplets can be formed from the crown sheet, resulting in splash. The present study results in three major contributions. (1) A theoretical model is developed to predict the expansion of the crown base. The model with an introduced energy loss factor is shown to be in satisfactory agreement with our experimental observations of drop impact on both stationary and flowing films. The energy loss factor is correlated to the properties of the film and drop. (2) Analysis is conducted to derive an equation for evaluating the stretching rate of the rising crown sheet, which is the local gradient of the rising velocity at the top edge of the crown sheet. It shows that the highest stretching rate appears where the drop spreading flow is right opposite to the film flow, which helps explain why the same location is most probable for splash to take place. (3) A parameter as a function of modified Weber and Reynolds numbers is defined to predict splash and nonsplash of drop impact on flowing films. The two nondimensional numbers evaluate the competition of the two flows (drop and film) against viscosity and surface tension effects. A threshold value of the parameter is found for the occurrence of splash impact on flowing films. PMID:26651777
Viscoelastic Flows in Simple Liquids Generated by Vibrating Nanostructures
NASA Astrophysics Data System (ADS)
Sader, John; Pelton, Matthew; Chakraborty, Debadi; Malachosky, Edward; Guyot-Sionnest, Philippe
2014-11-01
Newtonian fluid mechanics, in which the shear stress is proportional to the strain rate, is synonymous with the flow of simple liquids like water. We report the measurement and theoretical verification of non-Newtonian, viscoelastic flow phenomena produced by the high-frequency (>20 GHz) vibration of gold nanoparticles immersed in water-glycerol mixtures. The observed viscoelasticity is not due to molecular confinement, but is a bulk continuum effect arising from the short time scale of vibration. This represents the first direct mechanical measurement of the intrinsic viscoelastic properties of simple bulk liquids, and opens a new paradigm for understanding extremely high frequency fluid mechanics, nanoscale sensing technologies, and biophysical processes.
NASA Astrophysics Data System (ADS)
El Kadi Abderrezzak, Kamal; Die Moran, Andrés; Tassi, Pablo; Ata, Riadh; Hervouet, Jean-Michel
2016-07-01
Bank erosion can be an important form of morphological adjustment in rivers. With the advances made in computational techniques, two-dimensional (2D) depth-averaged numerical models have become valuable tools for resolving many engineering problems dealing with sediment transport. The objective of this research work is to present a simple, new, bank-erosion operator that is integrated into a 2D Saint-Venant-Exner morphodynamic model. The numerical code is based on an unstructured grid of triangular elements and finite-element algorithms. The slope of each element in the grid is compared to the angle of repose of the bank material. Elements for which the slope is too steep are tilted to bring them to the angle of repose along a horizontal axis defined such that the volume loss above the axis is equal to the volume gain below, thus ensuring mass balance. The model performance is assessed using data from laboratory flume experiments and a scale model of the Old Rhine. For the flume experiment case with uniform bank material, relevant results are obtained for bank geometry changes. For the more challenging case (i.e. scale model of the Old Rhine with non-uniform bank material), the numerical model is capable of reproducing the main features of the bank failure, induced by the newly designed groynes, as well as the transport of the mobilized sediment material downstream. Some deviations between the computed results and measured data are, however, observed. They are ascribed to the effects of three-dimensional (3D) flow structures, pore pressure and cohesion, which are not considered in the present 2D model.
Electromagnetically Sustained Liquid Metal Flow for Feedback Stabilization Studies
NASA Astrophysics Data System (ADS)
Mirhoseini, Seyyed Mohammad; Volpe, Francesco
2015-11-01
Liquid metal walls in fusion reactors, whether nearly static or rapidly flowing, will be subject to instabilities that will make them locally bulge, thus entering in contact with the plasma, or deplete, hence exposing the underlying solid substrate. To prevent this, research has begun at Columbia University to create liquid metal flows and demonstrate their stabilization by electromagnetic forces, adjusted in feedback with thickness measurements. Here we present initial results regarding the sustainment of a flow of Galinstan (a gallium, indium, tin alloy) by a special pump consisting of a ferromagnetic rotor, with permanent magnets mounted on it. The magnetic field is partly ``frozen'' in the liquid metal surrounding the rotor. Therefore, as the field rotates, the liquid metal rotates as well, although with a slip factor. This solution was preferred to conventional pumps, which would enter in electrical contact with the metal flow. The pump, 3D-printed at Columbia, allows to adjust the flow-velocity from few mm/s to several cm/s.
Confinement effects on liquid-flow characteristics in carbon nanotubes
NASA Astrophysics Data System (ADS)
Yasuoka, Haruka; Takahama, Ryo; Kaneda, Masayuki; Suga, Kazuhiko
2015-12-01
Liquid flow dynamics through the armchair (6 ,6 )-(160 ,160 ) carbon nanotubes (CNTs) is elucidated by molecular dynamics simulations. The liquid is modeled by nonpolar argon atoms to understand the fundamental flow physics. The velocity profiles and slip lengths are discussed considering the radial distributions of the fluid density by the presently proposed finite difference-based velocity fitting method. It is found that as the CNT diameter D increases, the slip length and the flow rate enhancement show three-step transitional profiles in the region of D ≤2.3 nm. The slip length and the flow rate stepwise increase at the first transition while they drop at the second and third transitions. The first transition corresponds to the structural change from the single-file chain to single-ring structures of the molecule cluster. The second and third transitions take place when the ring structure starts to develop another inner layer.
Vortex shedding flowmeters for liquids at high flow velocities
NASA Technical Reports Server (NTRS)
Siegwarth, J. D.
1985-01-01
A number of vortex shedding flowmeter designs for flow measurements in liquid oxygen ducts on the space shuttle main engines have been tested in a high head water flow test facility. The results have shown that a vortex shedding element or vane spanning the duct can give a linear response to an average flow velocity of 46 m/s (150 ft/s) in a 1 1/2 inch nominal (41 mm actual) diameter duct while a vane partially spanning the duct can give a linear response to velocities exceeding 55 m/s (180 ft/s). The maximum pressure drops across the flow sensing elements extrapolate to less than 0.7 MPa (100 psi) at 56 m/s (184 ft/s) for liquid oxygen. The test results indicate that the vanes probably cannot be scaled up with pipe size, at least not linearly.
Thermal dispersion in vertical gas-liquid flows with foaming and non-foaming liquids
Pino, L.R.Z.; Saez, A.E.
1995-05-01
Heat transfer experiments have been performed in gas-liquid upwards flow in a vertical column with non-foaming (water) and foaming (kerosene) liquids. The main purpose of the experiments has been to characterized the degree of thermal mixing in the system. For the range of conditions employed, the nonfoaming liquid exhibits complete mixing a low liquid superficial velocities. An increased in liquid velocity leads to incomplete mixing. In the latter case, the thermal dispersion coefficient at low gas superficial velocities is larger than what correlations in the literature predict. For the foaming liquid, when foaming and bubbling regions coexist in the bubble column, each region behaves as a completely-mixed subsystem.
Liquid rocket engine centrifugal flow turbopumps. [design criteria
NASA Technical Reports Server (NTRS)
1973-01-01
Design criteria and recommended practices are discussed for the following configurations selected from the design sequence of a liquid rocket engine centrifugal flow turbopump: (1) pump performance including speed, efficiency, and flow range; (2) impeller; (3) housing; and (4) thrust balance system. Hydrodynamic, structural, and mechanical problems are addressed for the achievement of required pump performance within the constraints imposed by the engine/turbopump system. Materials and fabrication specifications are also discussed.
The use of liquid crystals for surface flow visualization
NASA Technical Reports Server (NTRS)
Smith, Stephen C.
1990-01-01
The use of shear-sensitive liquid crystals has become an established technique for diagnostic flow visualization. This technique has been demonstrated to illustrate laminar boundary-layer transition, laminar bubbles, shocks, and separation in flight and wind-tunnel environments. Typical results demonstrate the range of flow features which can be illustrated and some of the challenges and pitfalls which must be addressed. A few remaining issues are discussed which should be resolved to develop this technique to full maturity.
Estimation of Liquid Wall and Interfacial Shear Stress in Horizontal Stratified Gas-liquid Pipe Flow
NASA Astrophysics Data System (ADS)
Liu, Yiping; Zhang, Hua; Wang, Jing
2007-06-01
A modified two-phase shear stress calculation method for pipe flow problems is explored. A force balance has been set up on the control volume of liquid phase to determine the interfacial friction factor by employing both the measured pressure gradient and liquid height. The gradient of height of liquid layer has been taken into account, which is suitable for the case where the interface may be smooth, rippled or wavy. The correlation of model indicates that the careful estimation for liquid-wall shear stress is necessary, and the assumption of a stationary liquid element is not applicable for the case of higher gas flow rates. The interfacial friction factor evaluated indirectly from experimental liquid height and pressure loss measurements, which are obtained in 50mm ID pipeline for air and water in cocurrent stratified flow, is used to achieve its correlation with the combination of characteristic parameters. The evaluation of new correlation has been conducted by the comparison of the predicted pressure drop with the experimental data. The performance of correlation depends on the form of the gas-liquid interface.
NASA Astrophysics Data System (ADS)
Yang, PeiPei; Wen, Zhi; Dou, RuiFeng; Liu, Xunliang
2016-08-01
Flow and heat transfer through a 2D random porous medium are studied by using the lattice Boltzmann method (LBM). For the random porous medium, the influence of disordered cylinder arrangement on permeability and Nusselt number are investigated. Results indicate that the permeability and Nusselt number for different cylinder locations are unequal even with the same number and size of cylinders. New correlations for the permeability and coefficient b‧Den of the Forchheimer equation are proposed for random porous medium composed of Gaussian distributed circular cylinders. Furthermore, a general set of heat transfer correlations is proposed and compared with existing experimental data and empirical correlations. Our results show that the Nu number increases with the increase of the porosity, hence heat transfer is found to be accurate considering the effect of porosity.
Leandro, Jorge; Martins, Ricardo
2016-01-01
Pluvial flooding in urban areas is characterized by a gradually varying inundation process caused by surcharge of the sewer manholes. Therefore urban flood models need to simulate the interaction between the sewer network and the overland flow in order to accurately predict the flood inundation extents. In this work we present a methodology for linking 2D overland flow models with the storm sewer model SWMM 5. SWMM 5 is a well-known free open-source code originally developed in 1971. The latest major release saw its structure re-written in C ++ allowing it to be compiled as a command line executable or through a series of calls made to function inside a dynamic link library (DLL). The methodology developed herein is written inside the same DLL in C + +, and is able to simulate the bi-directional interaction between both models during simulation. Validation is done in a real case study with an existing urban flood coupled model. The novelty herein is that the new methodology can be added to SWMM without the need for editing SWMM's original code. Furthermore, it is directly applicable to other coupled overland flow models aiming to use SWMM 5 as the sewer network model. PMID:27332848
Two parametric flow measurement in gas-liquid two-phase flow
NASA Astrophysics Data System (ADS)
Chen, Z.; Chen, C.; Xu, Y.; Zhao, Z.
The importance and current development of two parametric measurement during two-phase flow are briefly reviewed in this paper. Gas-liquid two-phase two parametric metering experiments were conducted by using an oval gear meter and a sharp edged orifice mounted in series in a horizontal pipe. Compressed air and water were used as gas and liquid phases respectively. The correlations, which can be used to predict the total flow rate and volumetric quality of two-phase flow or volumetric flow rate of each phase, have also been proposed in this paper. Comparison of the calculated values of flow rate of each phase from the correlations with the test data showed that the root mean square fractional deviation for gas flow rate is 2.9 percent and for liquid flow rate 4.4 percent. The method proposed in this paper can be used to measure the gas and liquid flow rate in two-phase flow region without having to separate the phases.
Thermocapillary flows in two-fluids liquid bridges
NASA Astrophysics Data System (ADS)
Viviani, A.; Golia, C.
2003-12-01
In this paper we consider the flow and interfaces deformation in non-isothermal two-liquids bridges, i.e. in liquid bridges held between two parallel planar disks, posed at different temperature, which are composed by two coaxial immiscible liquid columns, an inner column of liquid ( a) forming an axisymmetric interface with an outer annular column of liquid ( b) bounded by a free surface from the external still gas. The motion in the two bulk phases arises due to surface gradients of the interface tensions, induced by the imposed temperature difference, both at the liquid-liquid interface and at the external free surface; for the interface tensions it is assumed a linear dependence on the temperature. Under the hypothesis of Reynolds, Peclet and capillary numbers very small, the field equations are expanded in a series of successive linear approximations; the zeroth-order approximation is the Stokes problem, that is analytically solved via separation of variables in terms of infinite series of modified first-order Bessel functions of first and second kind and Papkovitch-Fadle bi-orthogonal eigenfunctions. To improve convergence of the series, Cesaro sums are used. The solution is given for the zeroth order temperature, velocity and pressure fields and for the first-order deviation of the interfaces from the hydrostatic shape. Streamlines, velocity profiles and interface shapes are presented and discussed in terms of Marangoni numbers, viscosity ratio of the two bulk phases and aspect ratios of the two liquid columns.
Thermohydrodynamic Analysis of Cryogenic Liquid Turbulent Flow Fluid Film Bearings
NASA Technical Reports Server (NTRS)
SanAndres, Luis
1996-01-01
Computational programs developed for the thermal analysis of tilting and flexure-pad hybrid bearings, and the unsteady flow and transient response of a point mass rotor supported on fluid film bearings are described. The motion of a cryogenic liquid on the thin film annular region of a fluid film bearing is described by a set of mass and momentum conservation, and energy transport equations for the turbulent bulk-flow velocities and pressure, and accompanied by thermophysical state equations for evaluation of the fluid material properties. Zeroth-order equations describe the fluid flow field for a journal static equilibrium position, while first-order (linear) equations govern the fluid flow for small amplitude-journal center translational motions. Solution to the zeroth-order flow field equations provides the bearing flow rate, load capacity, drag torque and temperature rise. Solution to the first-order equations determines the rotordynamic force coefficients due to journal radial motions.
Asymmetric energy flow in liquid alkylbenzenes: A computational study
Leitner, David M.; Pandey, Hari Datt
2015-10-14
Ultrafast IR-Raman experiments on substituted benzenes [B. C. Pein et al., J. Phys. Chem. B 117, 10898–10904 (2013)] reveal that energy can flow more efficiently in one direction along a molecule than in others. We carry out a computational study of energy flow in the three alkyl benzenes, toluene, isopropylbenzene, and t-butylbenzene, studied in these experiments, and find an asymmetry in the flow of vibrational energy between the two chemical groups of the molecule due to quantum mechanical vibrational relaxation bottlenecks, which give rise to a preferred direction of energy flow. We compare energy flow computed for all modes of the three alkylbenzenes over the relaxation time into the liquid with energy flow through the subset of modes monitored in the time-resolved Raman experiments and find qualitatively similar results when using the subset compared to all the modes.
Dynamic Modeling Strategy for Flow Regime Transition in Gas-Liquid Two-Phase Flows
Xia Wang; Xiaodong Sun; Benjamin Doup; Haihua Zhao
2012-12-01
In modeling gas-liquid two-phase flows, the concept of flow regimes has been widely used to characterize the global interfacial structure of the flows. Nearly all constitutive relations that provide closures to the interfacial transfers in two-phase flow models, such as the two-fluid model, are flow regime dependent. Current nuclear reactor safety analysis codes, such as RELAP5, classify flow regimes using flow regime maps or transition criteria that were developed for steady-state, fully-developed flows. As twophase flows are dynamic in nature, it is important to model the flow regime transitions dynamically to more accurately predict the two-phase flows. The present work aims to develop a dynamic modeling strategy to determine flow regimes in gas-liquid two-phase flows through introduction of interfacial area transport equations (IATEs) within the framework of a two-fluid model. The IATE is a transport equation that models the interfacial area concentration by considering the creation of the interfacial area, fluid particle (bubble or liquid droplet) disintegration, boiling and evaporation, and the destruction of the interfacial area, fluid particle coalescence and condensation. For flow regimes beyond bubbly flows, a two-group IATE has been proposed, in which bubbles are divided into two groups based on their size and shapes, namely group-1 and group-2 bubbles. A preliminary approach to dynamically identify the flow regimes is discussed, in which discriminator s are based on the predicted information, such as the void fraction and interfacial area concentration. The flow regime predicted with this method shows good agreement with the experimental observations.
Effect of liquid viscosity on wave behavior in gas-liquid two-phase flow
Kondo, Yoshiyuki; Mori, Koji; Yagishita, Takuya; Nakabo, Akinobu
1999-07-01
Measurements of time-spatial distributions of liquid holdups for the vertical upward gas-liquid two-phase flow were carried out by using the supermultiple cross-sectional mean liquid holdup probes (S-CHOP) and the semi-supermultiple point-electrode probes (SS-PEP) in the wide range of superficial gas and liquid velocity, j{sub g} and j{sub {ell}}, and the liquid kinematic viscosities were {nu}{sub {ell}} = 1 x 10{sup {minus}6}, 10 x 10{sup {minus}6} and 20 x 10{sup {minus}6} m{sup 1}/s. The time-spatial maps of wave behavior and the interfacial profiles were presented. Close inspection of these results reveals that there also exist huge waves and disturbance waves in the higher liquid viscosity conditions. To clarify the characteristics of these waves, the wave-vein analysis and the cluster analysis by K-mean algorithm were applied. These methods distinguished huge wave and disturbance wave objectively. The appearance regions of liquid slug, huge wave, and disturbance wave for each liquid viscosity condition were presented and the effects of liquid viscosity on them were discussed. Furthermore, velocity, width and height of these waves were determined, and the effects of liquid viscosity on them were clarified.
How do entangled polymeric liquids flow?
NASA Astrophysics Data System (ADS)
Sundar Ravindranath, Sham; Wang, Shi-Qing
2009-03-01
This work focused on investigating fundamental questions in polymer dynamics such as how entangled polymeric liquids respond to fast external deformation. By developing an effective particle tracking velocimetric (PTV) method, along with conventional rheometric measurements, new insights can be gained into the phenomenology of entangled polymers in presence of startup shear, step strain and large amplitude oscillatory shear (LAOS). During startup shear of well entangled systems, the shear field becomes inhomogeneous after the stress overshoot for a range of applied shear rates beyond the Newtonian region [1]. The emergence of shear banding after stress overshoot helped us to identify the stress overshoot as indicating yielding, whose characteristics obey some scaling laws. In step shear, contrary to the conventional perception that entangled polymers would undergo quiescent relaxation, the PTV observations reveal macroscopic motions after shear cessation [2]. The recoil-like macroscopic motions appears to reflect an elastic breakdown of the entanglement network due to sufficient build-up of retractive forces. LAOS experiments also demonstrate that entangled polymers cannot sustain a high magnitude of fast deformation without undergoing cohesive failure [3]. [1] Macromolecules 2008, 41, 2663 [2] Macromolecules 2007, 40, 8031 [3] J. Rheol. 2008, 52, 341.
NASA Technical Reports Server (NTRS)
Hassan, M. I.; Kuwana, K.; Saito, K.
2001-01-01
In the past, we measured three-D flow structure in the liquid and gas phases that were created by a spreading flame over liquid fuels. In that effort, we employed several different techniques including our original laser sheet particle tracking (LSPT) technique, which is capable of measuring transient 2-D flow structures. Recently we obtained a state-of-the-art integrated particle image velocimetry (IPIV), whose function is similar to LSPT, but it has an integrated data recording and processing system. To evaluate the accuracy of our IPIV system, we conducted a series of flame spread tests using the same experimental apparatus that we used in our previous flame spread studies and obtained a series of 2-D flow profiles corresponding to our previous LSPT measurements. We confirmed that both LSPT and IPIV techniques produced similar data, but IPIV data contains more detailed flow structures than LSPT data. Here we present some of newly obtained IPIV flow structure data, and discuss the role of gravity in the flame-induced flow structures. Note that the application of IPIV to our flame spread problems is not straightforward, and it required several preliminary tests for its accuracy including this IPIV comparison to LSPT.
CFD simulation on the turbulent mixing flow performance of the liquid-liquid ejector
NASA Astrophysics Data System (ADS)
An, W. Z.; Bie, H. Y.; Liu, C. C.; Hao, Z. R.
2016-05-01
In order to study the flow performance of the liquid-liquid ejector, 3D ejector simulation models were established to investigate the influences of suction angle, suction number and working condition on the ejector performance. The simulation results showed that when the suction angle was 60°, the total pressure was in equilibrium state. The double suction ejector would induced more vortexes in the suction chamber than that of the single suction ejector, and the turbulent intensity of the fluid inside the ejector was bigger, however, it also caused much more loss in energy. When the working pressure was lower than 0.6 MPa, the liquid entrainment ratio increased rapidly. Once the working pressure reached 0.6 MPa, the liquid entrainment ratio basically remained unchanged. The mass flow rate of the suction medium increased with the increasing of suction pressure, and the differential pressure between the suction pressure and the working pressure at the nozzle also increased simultaneously.
Basic study on hot-wire flow meter in forced flow of liquid hydrogen
NASA Astrophysics Data System (ADS)
Oura, Y.; Shirai, Y.; Shiotsu, M.; Murakami, K.; Tatsumoto, H.; Naruo, Y.; Nonaka, S.; Kobayashi, H.; Inatani, Y.; Narita, N.
2014-01-01
Liquid hydrogen (LH2) is a key issue in a carbon-free energy infrastructure at the energy storage and transportation stage. The typical features of LH2 are low viscosity, large latent heat and small density, compared with other general liquids. It is necessary to measure a mass flow of liquid hydrogen with a simple and compact method, especially in a two phase separate flow condition. We have proposed applying a hot-wire type flow meter, which is usually used a for gas flow meter, to LH2 flow due to the quite low viscosity and density. A test model of a compact LH2 hot-wire flow meter to measure local flow velocities near and around an inside perimeter of a horizontal tube by resistance thermometry was designed and made. The model flow meter consists of two thin heater wires made of manganin fixed in a 10 mm-diameter and 40 mm-length tube flow path made of GFRP. Each rigid heater wire was set twisted by 90 degrees from the inlet to the outlet along the inner wall. In other words, the wires were aslant with regard to the LH2 stream line. The heated wire was cooled by flowing LH2, and the flow velocity was obtained by means of the difference of the cooling characteristic in response to the flow velocity. In this report, we show results on the basic experiments with the model LH2 hot-wire flow meter. First, the heat transfer characteristics of the two heater wires for several LH2 flow velocities were measured. Second, the heating current was controlled to keep the wire temperature constant for various flow velocities. The relations between the flow velocity and the heating current were measured. The feasibility of the proposed model was confirmed.
Liquid-Crystal Coats Help Make Flows Visible
NASA Technical Reports Server (NTRS)
Holmes, Bruce J.; Obara, Clifford J.
1991-01-01
Visible indication of transition of boundary layer from laminar to turbulent flow plays important role in aerodynamic tests in wind tunnels and in flight. In newly developed method, liquid-crystal coats used to make visible such features of boundary-layer flows as transitions, separations, and locations of shocks. Changes of color rapid and reversible. For flight applications, provides capability for making transitions visible throughout almost entire altitude and speed ranges of subsonic aircraft. Also applicable to visible indication of supersonic flows and suitable for general use in high- and low-speed wind-tunnel and water-tunnel testing.
Fluid flow effects in evaporation from liquid-vapor meniscus
Khrustalev, D.; Faghri, A.
1996-12-31
A mathematical model of the evaporating liquid-vapor meniscus in a capillary slot has been developed. The model includes two-dimensional steady-state momentum conservation and energy equations for both the vapor and liquid phases, and incorporates the existing simplified one-dimensional model of the evaporating microfilm. The numerical results, obtained for water, demonstrate the importance of accounting for the fluid flow in calculating the effective evaporative heat transfer coefficient and the superheat of the vapor over the liquid-vapor meniscus due to the heat transfer from the heated wall. With higher heat fluxes, a recirculation zone appears in the vapor near the heated wall due to the extensive evaporation in the thin-film region of the liquid-vapor meniscus.
Flow Visualization of Liquid Hydrogen Line Chilldown Tests
NASA Technical Reports Server (NTRS)
Rame, Enrique; Hartwig, Jason W.; McQuillen John B.
2014-01-01
We present experimental measurements of wall and fluid temperature during chill-down tests of a warm cryogenic line with liquid hydrogen. Synchronized video and fluid temperature measurements are used to interpret stream temperature profiles versus time. When cold liquid hydrogen starts to flow into the warm line, a sequence of flow regimes, spanning from all-vapor at the outset to bubbly with continuum liquid at the end can be observed at a location far downstream of the cold inlet. In this paper we propose interpretations to the observed flow regimes and fluid temperature histories for two chilldown methods, viz. trickle (i.e. continuous) flow and pulse flow. Calculations of heat flux from the wall to the fluid versus wall temperature indicate the presence of the transition/nucleate boiling regimes only. The present tests, run at typical Reynolds numbers of approx O(10 (exp 5)), are in sharp contrast to similar tests conducted at lower Reynolds numbers where a well-defined film boiling region is observed.
Liquid plug flow in a vertical two-dimensional channel
NASA Astrophysics Data System (ADS)
Bull, Joseph; Halpern, David; Grotberg, James
2001-11-01
Gravity and pressure driven liquid plug flow in a two-dimensional vertical channel is investigated as a model of instilled liquid transport in the lungs. There are a number of clinical situations in which liquids are instilled into the lungs. Of particular interest is liquid ventilation where perfluorocarbon liquids are delivered to the lung and subsequently used for ventilation in place of gas. Additionally the perfuorocarbon can be used as a carrier for drugs or genetic material. Some other examples of liquid instillation into the lungs include surfactant replacement therapy, lung lavage, and cardio-pulmonary resuscitation. The desired distribution of liquid depends on the application. Our model is developed using the Stokes equation subject to interfacial and wall boundary conditions, and is solved using the boundary element method. We obtain steady-state and time-dependent solutions. As the plug propagates along the thin-film-lined channel, it takes up liquid from the leading film and deposit liquid in the trailing film. The trailing film thickness, interface shapes and plug speed are determined as functions of the parameters of the problem, Bond number, driving pressure, and leading film thickness and initial plug length for the time-dependent problem. These results are important clinically since the trailing film thickness determines when the plug ruptures affecting the ultimate liquid distribution, and thicker films can result in airway closure. This research was supported by NIH grants HL41126, HL64373, and HL54224-04S1. J.L. Bull is a Parker B. Francis Fellow in Pulmonary Research.
Topological transitions in unidirectional flow of nematic liquid crystal
NASA Astrophysics Data System (ADS)
Cummings, Linda; Anderson, Thomas; Mema, Ensela; Kondic, Lou
2015-11-01
Recent experiments by Sengupta et al. (Phys. Rev. Lett. 2013) revealed interesting transitions that can occur in flow of nematic liquid crystal under carefully controlled conditions within a long microfluidic channel of rectangular cross-section, with homeotropic anchoring at the walls. At low flow rates the director field of the nematic adopts a configuration that is dominated by the surface anchoring, being nearly parallel to the channel height direction over most of the cross-section; but at high flow rates there is a transition to a flow-dominated state, where the director configuration at the channel centerline is aligned with the flow (perpendicular to the channel height direction). We analyze simple channel-flow solutions to the Leslie-Ericksen model for nematics. We demonstrate that two solutions exist, at all flow rates, but that there is a transition between the elastic free energies of these solutions: the anchoring-dominated solution has the lowest energy at low flow rates, and the flow-dominated solution has lowest energy at high flow rates. NSF DMS 1211713.
Ultrasound Doppler Velocimetry Measurements in Turbulent Liquid Metal Channel Flow
NASA Astrophysics Data System (ADS)
Rivero, Michel; Jian, Dandan; Karcher, Christian; Cuevas, Sergio
2010-11-01
Control of molten metal flow using magnetic fields is important in industrial applications. The Electromagnetic Flow Control Channel (EFCO) is an experimental test facility, located at Ilmenau University of Technology, for the development of such kind of control systems. The working fluid is the low-melting liquid metal alloy GaInSn in eutectic composition. In this channel, flow control is realized by combining and coupling the non-contact flow driving technology of electromagnetic pumps based on rotating permanent magnets and the non-contact flow rate measurement technology termed Lorentz Force Velocimetry (LFV). The flow rate is adjusted by controlling the rotation rate of the permanent magnet system. Physically, LFV is based on measuring the force acting on a magnet system. This force is induced by the melt flow passing through the static magnetic field generated by the system and is proportional to the flow. To calibrate such flow meters, we apply UDV technique to measure and analyse both turbulent hydrodynamic and MHD flow profiles in EFCO at various Reynolds numbers.
Numerical modeling of liquid-liquid bi-propellant droplet/gas reacting flows
NASA Astrophysics Data System (ADS)
Tang, Yupai L.; Schuman, M. D.
1992-01-01
A liquid-liquid bipropellant capability for numerically simulating droplets and gas two-phase flows for impinging type rocket injectors was developed through modification of the KIVA-II computer program. This added feature of liquid-liquid bipropellant sprays makes it possible to analyze the impinging type injectors through prescribed drop size and velocity distributions near the point of impingement. Two sample cases for LOX/liquid propane were run at mixture ratios of 3.06 and 2.72 respectively for a 3.4-inch diameter rocket engine with a contraction ratio of four and an expansion ratio of two. The predicted performance as well as the chamber heat transfer were found to be in reasonable agreement with the experimental data.
Parallel magnetic resonance imaging of gas-liquid flows
NASA Astrophysics Data System (ADS)
Mueller, Christoph; Penn, Alexander; Pruessmann, Klaas P.
2015-03-01
Gas-liquids flows are commonly encountered in nature and industry. Experimental measurements of gas-liquid flows are challenging since such systems can be visually opaque and highly dynamic. Here we report the implementation of advanced magnetic resonance imaging (MRI) strategies allowing us to probe the dynamics (voidage and velocity measurements) of gas-liquid flows with ultra-fast acquisition speeds. Specifically, parallel MRI which exploits the spatial encoding capabilities of multiple receiver coils was implemented. To this end a tailored, 16 channels MR receive array was constructed and employed in the MR acquisition. A magnetic susceptibility matched gas-liquid system was set-up and used to probe the motion, splitting and coalescence of bubbles. The temporal and spatial resolution of our acquired data was 5 ms and 3.5 mm x 3.5 mm, respectively. The total field of view was 200 mm x 200 mm. We will conclude with an outlook of further possible advances in MRI that have the potential to reduce substantially the acquisition time, providing flexible gains in temporal and spatial resolution.
Analysis of Developing Gas/liquid Two-Phase Flows
Elena A. Tselishcheva; Michael Z. Podowski; Steven P. Antal; Donna Post Guillen; Matthias Beyer; Dirk Lucas
2010-06-01
The goal of this work is to develop a mechanistically based CFD model that can be used to simulate process equipment operating in the churn-turbulent regime. The simulations were performed using a state-of-the-art computational multiphase fluid dynamics code, NPHASE–CMFD [Antal et al,2000]. A complete four-field model, including the continuous liquid field and three dispersed gas fields representing bubbles of different sizes, was first carefully tested for numerical convergence and accuracy, and then used to reproduce the experimental results from the TOPFLOW test facility at Forschungszentrum Dresden-Rossendorf e.V. Institute of Safety Research [Prasser et al,2007]. Good progress has been made in simulating the churn-turbulent flows and comparison the NPHASE-CMFD simulations with TOPFLOW experimental data. The main objective of the paper is to demonstrate capability to predict the evolution of adiabatic churn-turbulent gas/liquid flows. The proposed modelling concept uses transport equations for the continuous liquid field and for dispersed bubble fields [Tselishcheva et al, 2009]. Along with closure laws based on interaction between bubbles and continuous liquid, the effect of height on air density has been included in the model. The figure below presents the developing flow results of the study, namely total void fraction at different axial locations along the TOPFLOW facility test section. The complete model description, as well as results of simulations and validation will be presented in the full paper.
Liquid and liquid–gas flows at all speeds
LeMartelot, S.; Nkonga, B.; Saurel, R.
2013-12-15
All speed flows and in particular low Mach number flow algorithms are addressed for the numerical approximation of the Kapila et al. [1] multiphase flow model. This model is valid for fluid mixtures evolving in mechanical equilibrium but out of temperature equilibrium and is efficient for material interfaces computation separating miscible and non-miscible fluids. In this context, the interface is considered as a numerically diffused zone, captured as well as all present waves (shocks, expansion waves). The same flow model can be used to solve cavitating and boiling flows [2]. Many applications occurring with liquid–gas interfaces and cavitating flows involve a very wide range of Mach number, from 10{sup −3} to supersonic (and even hypersonic) conditions with respect to the mixture sound speed. It is thus important to address numerical methods free of restrictions regarding the Mach number. To do this, a preconditioned Riemann solver is built and embedded into the Godunov explicit scheme. It is shown that this method converges to exact solutions but needs too small time steps to be efficient. An implicit version is then derived, first in one dimension and second in the frame of 2D unstructured meshes. Two-phase flow preconditioning is then addressed in the frame of the Saurel et al. [3] algorithm. Modifications of the preconditioned Riemann solver are needed and detailed. Convergence of both single phase and two-phase numerical solutions are demonstrated with the help of single phase and two-phase steady nozzle flow solutions. Last, the method is illustrated by the computation of real cavitating flows in Venturi nozzles. Vapour pocket size and instability frequencies are reproduced by the model and method without using any adjustable parameter.
Liquid-liquid extraction based on a new flow pattern: Two-fluid Taylor-Couette flow
NASA Astrophysics Data System (ADS)
Baier, Gretchen
The exploitation of flow instabilities that can occur in rotating flows is investigated as a new approach to liquid extraction. Two immiscible liquids are radially stratified by centrifugal force in the annulus between corotating coaxial cylinders. The inner cylinder is rotated above a critical speed to form Taylor vortices in one or both of the fluids. This flow pattern produces a relatively small amount interfacial surface area that is of highly active for interphase mass transfer. Continuous processing is also possible with the addition of countercurrent axial flow. The present study includes: (1)A review of aqueous- aqueous and reversed micelle extraction techniques, the commercially available centrifugal extractors, and one fluid Taylor-Couette flow and its variations. (2)A theoretical analysis to predict the onset of the two- fluid Taylor-Couette instability in the presence of countercurrent axial flow. (3)Theoretical predictions for interphase mass transfer using penetration theory and computational fluid dynamics. (4)The demonstration of two-fluid Taylor-Couette flow with countercurrent axial flow in the laboratory, including: (1) fluid mechanics studies to determine the onset of vortices, and (2) mass transfer studies to characterize intraphase and interphase mass transfer. The agreement between the experiments and theory is good for both the fluid mechanics and the mass transfer. Furthermore, the extraction performance is quite promising with the mass transfer coefficient approximately proportional to the vortex strength. Even higher extraction efficiencies should be obtainable with even larger relative rotation rates or cylinder modification to promote vortex formation. Besides two-fluid Taylor-Couette flow, other instabilities can also occur. With low viscosity fluids at low rotation rates, the ``barber pole'' pattern is observed experimentally and is believed to be a lingering gravitational effect. At high countercurrent axial flowrates, the linear
Asymptotic and numerical analysis of electrohydrodynamic flows of dielectric liquid.
Suh, Y K; Baek, K H; Cho, D S
2013-08-01
We perform an asymptotic analysis of electrohydrodynamic (EHD) flow of nonpolar liquid subjected to an external, nonuniform electric field. The domain of interest covers the bulk as well as the thin dissociation layers (DSLs) near the electrodes. Outer (i.e., bulk) equations for the ion transport in hierarchical order of perturbation parameters can be expressed in linear form, whereas the inner (i.e., DSL) equations take a nonlinear form. We derive a simple formula in terms of various parameters which can be used to estimate the relative importance of the DSL-driven flow compared with the bulk-driven flow. EHD flow over a pair of cylindrical electrodes is then solved asymptotically and numerically. It is found that in large geometric scale and high ion concentration the EHD flow is dominated by the bulk-charge-induced flow. As the scale and concentration are decreased, the DSL-driven slip velocity increases and the resultant flow tends to dominate the domain and finally leads to flow reversal. We also conduct a flow-visualization experiment to verify the analysis and attain good agreement between the two results with parameter tuning. We finally show, based on the comparison of experimental and numerical solutions, that the rate of free-ion generation (dissociation) should be less than the one predicted from the existing formula. PMID:24032920
Liquid chromatography/Fourier transform IR spectrometry interface flow cell
Johnson, Charles C.; Taylor, Larry T.
1986-01-01
A zero dead volume (ZDV) microbore high performance liquid chromatography (.mu.HPLC)/Fourier transform infrared (FTIR) interface flow cell includes an IR transparent crystal having a small diameter bore therein through which a sample liquid is passed. The interface flow cell further includes a metal holder in combination with a pair of inner, compressible seals for directly coupling the thus configured spectrometric flow cell to the outlet of a .mu.HPLC column end fitting to minimize the transfer volume of the effluents exiting the .mu.HPLC column which exhibit excellent flow characteristics due to the essentially unencumbered, open-flow design. The IR beam passes transverse to the sample flow through the circular bore within the IR transparent crystal, which is preferably comprised of potassium bromide (KBr) or calcium fluoride (CaF.sub.2), so as to minimize interference patterns and vignetting encountered in conventional parallel-plate IR cells. The long IR beam pathlength and lensing effect of the circular cross-section of the sample volume in combination with the refractive index differences between the solvent and the transparent crystal serve to focus the IR beam in enhancing sample detection sensitivity by an order of magnitude.
Liquid chromatography/Fourier transform IR spectrometry interface flow cell
Johnson, C.C.; Taylor, L.T.
1985-01-04
A zero dead volume (ZDV) microbore high performance liquid chromatography (..mu.. HPLC)/Fourier transform infrared (FTIR) interface flow cell includes an IR transparent crystal having a small diameter bore therein through which a sample liquid is passed. The interface flow cell further includes a metal holder in combination with a pair of inner, compressible seals for directly coupling the thus configured spectrometric flow cell to the outlet of a ..mu.. HPLC column end fitting to minimize the transfer volume of the effluents exiting the ..mu.. HPLC column which exhibit excellent flow characteristics due to the essentially unencumbered, open-flow design. The IR beam passes transverse to the sample flow through the circular bore within the IR transparent crystal, which is preferably comprised of potassium bromide (KBr) or calcium fluoride (CaF/sub 2/), so as to minimize interference patterns and vignetting encountered in conventional parallel-plate IR cells. The long IR beam pathlength and lensing effect of the circular cross-section of the sample volume in combination with the refractive index differences between the solvent and the transparent crystal serve to focus the IR beam in enhancing sample detection sensitivity by an order of magnitude.
Study of interfacial behavior in cocurrent gas-liquid flows
McCready, M.J.
1990-01-01
We have examined the mechanism of formation of solitary waves on gas-liquid flows and found, that these form from existing periodic waves which have sufficiently large ({approximately}1.5 to 2 depending upon fluid properties) amplitude to liquid layer-thickness ratios. The exact process for the wave shape change is not understood but it does not seem to be related to the wave steepness (amplitude/wavelength) or to separation of gas flow over the waves. The observed confinement of solitary waves to low liquid Reynolds numbers results because the necessary large precursor waves do not form if the wave speed dispersion is too large or if the wavelength of the dominant waves is too short, as occurs for higher Re{sub L}. Measurements of interface tracings and calculations of power spectra and bispectra as a function of flow distance for conditions close to neutral stability reveal that the initially, linearly unstable mode is stabilized by formation of overtones which are linearly stable and can dissipate energy. As a result, a stable wave field can occur. Mode equations, which include quadratic nonlinearities, can model this process to the extent of producing some degree of quantitative predictions for the amplitudes of the wave modes. However, a complete picture of the wave field must include sidebands as well because these are observed for some flow conditions. 34 refs., 12 figs., 2 tabs.
Transition of Thermocapillary Flow in Low Prandtl Number Liquid Bridge
NASA Astrophysics Data System (ADS)
Sasaki, Hiroei; Matsumoto, Satoshi; Yoda, Erika; Imaishi, Nobuyuki; Yoda, Shinichi
2005-11-01
An experimental study of thermocapillary convection in the half-zone liquid bridge of low Prandtl number fluid was performed to observe the transition behavior from steady to oscillatory flows. In thermocapillary convection, one of the still open problems is the observation of onset of oscillatory flow in low Prandtl number fluids. Numerical simulations predicted that there would be two transition points which were a first and second critical Marangoni number (Mac1 and Mac2). However, an experimental verification has not been performed previously because of its difficulties. A molten tin was used as test fluid and a liquid bridge configuration was employed. The temperature distribution at the interface between the liquid bridge and the cold disk was measured by using several fine thermocouples. It could be experimentally detected that the axisymmetric steady flow changes to three-dimensional steady one with increasing the temperature difference. At higher temperature difference, onset of oscillatory flow was also observed. Experimental results concerning the critical Marangoni numbers agreed very well with numerical simulation.
Ramírez-Miquet, Evelio E; Perchoux, Julien; Loubière, Karine; Tronche, Clément; Prat, Laurent; Sotolongo-Costa, Oscar
2016-01-01
Optical feedback interferometry (OFI) is a compact sensing technique with recent implementation for flow measurements in microchannels. We propose implementing OFI for the analysis at the microscale of multiphase flows starting with the case of parallel flows of two immiscible fluids. The velocity profiles in each phase were measured and the interface location estimated for several operating conditions. To the authors knowledge, this sensing technique is applied here for the first time to multiphase flows. Theoretical profiles issued from a model based on the Couette viscous flow approximation reproduce fairly well the experimental results. The sensing system and the analysis presented here provide a new tool for studying more complex interactions between immiscible fluids (such as liquid droplets flowing in a microchannel). PMID:27527178
Two-dimensional ultrasound Doppler velocimeter for flow mapping of unsteady liquid metal flows.
Franke, S; Lieske, H; Fischer, A; Büttner, L; Czarske, J; Räbiger, D; Eckert, S
2013-03-01
We present a novel pulsed-wave ultrasound Doppler system for fluid flow investigations being able to determine two-dimensional vector fields of flow velocities. Electromagnetically-driven liquid metal flows appear as an attractive application field for such a measurement system. Two linear ultrasound transducer arrays each equipped with 25 transducer elements are used to measure the flow field in a square plane of 67×67 mm(2). The application of advanced processing methods as a multi-beam operation, an interlaced echo signal acquisition and a segmental array technique enable high data acquisition rates and concurrently a high spatial resolution, which have not been obtained so far for flow measurements in liquid metals. The extended pulsing strategy and essential operation principles such as the multiplexing electronic concept will be presented within this paper. The capabilities of the measuring system make it suitable for investigations of non-transparent, turbulent flows. Here, we present measurements of liquid metal flows driven by a rotating magnetic field for demonstration purposes. The measuring setup realized here reveals details of the swirling fluid motion in a horizontal section of a cube. Frame acquisition rates up to 30 fps were achieved for a complete two-dimensional flow mapping. PMID:23186828
Mechanism of magnetic liquid flowing in the magnetic liquid seal gap of reciprocating shaft
NASA Astrophysics Data System (ADS)
Li, Decai; Xu, Haiping; He, Xinzhi; Lan, Huiqing
2005-03-01
In order to solve the problems that exist in the magnetic liquid seal of reciprocating shaft, we have set up an experimental facility, which composes a camera, microscope, step-by-step motor, pin roller screw, reciprocating motion shaft, pole pieces, permanent magnet and the magnetic liquid in the seal gap. Through the optical technology and image process of the experimental facility, we have studied the magnetic liquid flow in the seal gap when the reciprocating shaft moves with different velocities and strokes. This study specially concentrates on: (1) the regular pattern of such flow; (2) the loss quantity of magnetic liquid caused by the reciprocating motion shaft; (3) the failure reasons of this magnetic liquid seal; and (4) the design of a new structure for the magnetic liquid seal of reciprocating shaft. The application indicates that the new structure is very effective in some occasions. The new structure was accepted as the state patent in 2001 and authenticated as the achievement in the scientific research in 2002.
Low-gravity sensing of liquid/vapor interface and transient liquid flow
NASA Astrophysics Data System (ADS)
Jacobson, Saul A.; Korba, James M.; Lynnworth, Lawrence C.; Nguyen, Toan H.; Orton, George F.
1987-03-01
The work reported here deals mainly with tests on internally vaned cylindrical shell acrylic containers capped by hemispherical acrylic or aluminum end domes. Three different ultrasonic sensor techniques and one nucleonic technique presently are evaluated as possible solutions to the low-gravity liquid gauging problem. The ultrasonic techniques are as follows: use of a torsional wave sensor in which transit time is proportional to the integral of wetted distance x liquid density; integration of the flow rate output signal of a fast-response ultrasonic flowmeter; and use of multiplexed externally mounted 'point-sensor' transducers that sense transit times to liquid-gas interfaces. Using two commercial flowmeters and a thickness gauge modified for this particular project, bench tests were conducted at 1 g on liquids such as water, freon, and solvent 140, including both steady flow and pulsating flow with 40, 80, and 120 ms flow pulses. Subsequently, flight tests were conducted in the NASA KC-135 aircraft in which nearly 0-g conditions are obtainable for up to about 5 s in each of a number of repetitive parabolic flight trajectories. In some of these brief low-gravity flight tests freon was replaced with a higher-viscosity fuel to reduce sloshing and thereby obtain settled surfaces more quickly.
NASA Astrophysics Data System (ADS)
Prins, Steven L.; Blatchford, James; Olubuyide, Oluwamuyiwa; Riley, Deborah; Chang, Simon; Hong, Qi-Zhong; Kim, T. S.; Borges, Ricardo; Lin, Li
2009-03-01
As design rules and corresponding logic standard cell layouts continue to shrink node-on-node in accordance with Moore's law, complex 2D interactions, both intra-cell and between cells, become much more prominent. For example, in lithography, lack of scaling of λ/NA implies aggressive use of resolution enhancement techniques to meet logic scaling requirements-resulting in adverse effects such as 'forbidden pitches'-and also implies an increasing range of optical influence relative to cell size. These adverse effects are therefore expected to extend well beyond the cell boundary, leading to lithographic marginalities that occur only when a given cell is placed "in context" with other neighboring cells in a variable design environment [1]. This context dependence is greatly exacerbated by increased use of strain engineering techniques such as SiGe and dual-stress liners (DSL) to enhance transistor performance, both of which also have interaction lengths on the order of microns. The use of these techniques also breaks the formerly straightforward connection between lithographic 'shapes' and end-of-line electrical performance, thus making the formulation of design rules that are robust to process variations and complex 2D interactions more difficult. To address these issues, we have developed a first-principles-based simulation flow to study contextdependent electrical effects in layout, arising not only from lithography, but also from stress and interconnect parasitic effects. This flow is novel in that it can be applied to relatively large layout clips- required for context-dependent analysis-without relying on semi-empirical or 'black-box' models for the fundamental electrical effects. The first-principles-based approach is ideal for understanding contextdependent effects early in the design phase, so that they can be mitigated through restrictive design rules. The lithographic simulations have been discussed elsewhere [1] and will not be presented in detail. The
Voss, Clifford I.; Provost, A.M.
2002-01-01
SUTRA (Saturated-Unsaturated Transport) is a computer program that simulates fluid movement and the transport of either energy or dissolved substances in a subsurface environment. This upgraded version of SUTRA adds the capability for three-dimensional simulation to the former code (Voss, 1984), which allowed only two-dimensional simulation. The code employs a two- or three-dimensional finite-element and finite-difference method to approximate the governing equations that describe the two interdependent processes that are simulated: 1) fluid density-dependent saturated or unsaturated ground-water flow; and 2) either (a) transport of a solute in the ground water, in which the solute may be subject to: equilibrium adsorption on the porous matrix, and both first-order and zero-order production or decay; or (b) transport of thermal energy in the ground water and solid matrix of the aquifer. SUTRA may also be used to simulate simpler subsets of the above processes. A flow-direction-dependent dispersion process for anisotropic media is also provided by the code and is introduced in this report. As the primary calculated result, SUTRA provides fluid pressures and either solute concentrations or temperatures, as they vary with time, everywhere in the simulated subsurface system. SUTRA flow simulation may be employed for two-dimensional (2D) areal, cross sectional and three-dimensional (3D) modeling of saturated ground-water flow systems, and for cross sectional and 3D modeling of unsaturated zone flow. Solute-transport simulation using SUTRA may be employed to model natural or man-induced chemical-species transport including processes of solute sorption, production, and decay. For example, it may be applied to analyze ground-water contaminant transport problems and aquifer restoration designs. In addition, solute-transport simulation with SUTRA may be used for modeling of variable-density leachate movement, and for cross sectional modeling of saltwater intrusion in
Nonlinear flow behaviors of nematic liquid crystals in complex geometries
NASA Astrophysics Data System (ADS)
Araki, Takeaki
2013-02-01
We study nematic liquid crystals flowing in a regular-shaped porous medium by means of lattice Boltzmann simulations. With strong anchoring, the director field cannot align uniformly and topological defects are stably formed with a large number of possible configurations. In a quiescent state, each configuration is arrested since the energy barriers between possible configurations are higher than the thermal energy. If the flow speed is slow enough, the defect pattern is not changed from the initial quiescent configuration. Above a critical flow speed, the defect pattern transforms to a new stable configuration. In a regular-shaped porous matrix, there remain regularly aligned disclination loops. This regular pattern is maintained even after the flow is stopped.
Standard Flow Liquid Chromatography for Shotgun Proteomics in Bioenergy Research
González Fernández-Niño, Susana M.; Smith-Moritz, A. Michelle; Chan, Leanne Jade G.; Adams, Paul D.; Heazlewood, Joshua L.; Petzold, Christopher J.
2015-01-01
Over the past 10 years, the bioenergy field has realized significant achievements that have encouraged many follow on efforts centered on biosynthetic production of fuel-like compounds. Key to the success of these efforts has been transformational developments in feedstock characterization and metabolic engineering of biofuel-producing microbes. Lagging far behind these advancements are analytical methods to characterize and quantify systems of interest to the bioenergy field. In particular, the utilization of proteomics, while valuable for identifying novel enzymes and diagnosing problems associated with biofuel-producing microbes, is limited by a lack of robustness and limited throughput. Nano-flow liquid chromatography coupled to high-mass accuracy, high-resolution mass spectrometers has become the dominant approach for the analysis of complex proteomic samples, yet such assays still require dedicated experts for data acquisition, analysis, and instrument upkeep. The recent adoption of standard flow chromatography (ca. 0.5 mL/min) for targeted proteomics has highlighted the robust nature and increased throughput of this approach for sample analysis. Consequently, we assessed the applicability of standard flow liquid chromatography for shotgun proteomics using samples from Escherichia coli and Arabidopsis thaliana, organisms commonly used as model systems for lignocellulosic biofuels research. Employing 120 min gradients with standard flow chromatography, we were able to routinely identify nearly 800 proteins from E. coli samples; while for samples from Arabidopsis, over 1,000 proteins could be reliably identified. An examination of identified peptides indicated that the method was suitable for reproducible applications in shotgun proteomics. Standard flow liquid chromatography for shotgun proteomics provides a robust approach for the analysis of complex samples. To the best of our knowledge, this study represents the first attempt to validate the standard
Real-time precision concentration measurement for flowing liquid solutions
NASA Astrophysics Data System (ADS)
Krishna, V.; Fan, C. H.; Longtin, J. P.
2000-10-01
The precise, real-time measurement of liquid concentration is important in fundamental research, chemical analysis, mixing processes, and manufacturing, e.g., in the food and semiconductor industries. This work presents a laser-based, noninvasive technique to measure concentration changes of flowing liquids in real time. The essential components in the system include a 5 mW laser diode coupled to a single-mode optical fiber, a triangular optical cell, and a high-resolution beam position sensor. The instrument provides a large range of concentration measurement, typically 0%-100% for binary liquid mixtures, while providing a resolution on the order of 0.05% concentration or better. The experimental configuration is small, reliable, and inexpensive. Results are presented for NaCl and MgCl2 aqueous solutions with concentrations ranging from 0% to 25%, with very good agreement found between measured and true concentrations.
Flow Straightener for a Rotating-Drum Liquid Separator
NASA Technical Reports Server (NTRS)
O'Coin, James R.; Converse, David G.; Rethke, Donald W.
2004-01-01
A flow straightener has been incorporated into a rotary liquid separator that originally comprised an inlet tube, a shroud plate, an impeller, an inner drum, an outer drum, a housing, a pitot tube, and a hollow shaft motor. As a consequence of the original geometry of the impeller, shroud, inner drum, and hollow shaft, swirl was created in the airflow inside the hollow shaft during operation. The swirl speed was large enough to cause a significant pressure drop. The flow straightener consists of vanes on the back side of the shroud plate. These vanes compartmentalize the inside of the inner drum in such a way as to break up the flow path and thereby stop the air from swirling; as a result, the air enters the hollow shaft with a predominantly axial velocity instead of a swirl. Tests of the rotary liquid separator at an airflow rate of 10 cu ft/min (0.0047 cu m/s) revealed that the dynamic pressure drop was 8 in. of water (approx.=2 kPa) in the absence of the flow straightener and was reduced to 1 in. of water (approx.=0.25 kPa) in the presence of the flow straightener.
Orientational dynamics of nematic liquid crystals under shear flow
NASA Astrophysics Data System (ADS)
Rienäcker, G.; Hess, S.
The orientational dynamics of low molecular weight and polymeric nematic liquid crystals in a flow field is investigated, based on a nonlinear relaxation equation for the second rank alignment tensor. Various approximations are discussed: Assuming uniaxial alignment with a constant order parameter, the results of the Ericksen-Leslie theory are recovered. The detailed analysis to be presented here for plane Couette flow concerns (i) uniaxial alignment with a variable degree of order and (ii) the tensorial analysis involving the three symmetry-adapted components of the five components of the alignment tensor. The transitions between tumbling, wagging and aligning behavior observed in polymeric liquid crystals and described by the Doi theory of rod-like nematic polymers are recovered. Consequences for the rheological behavior are indicated.
Viscoelastic Flows in Simple Liquids Generated by Vibrating Nanostructures
NASA Astrophysics Data System (ADS)
Pelton, Matthew; Chakraborty, Debadi; Malachosky, Edward; Guyot-Sionnest, Philippe; Sader, John E.
2013-12-01
Newtonian fluid mechanics, in which the shear stress is proportional to the strain rate, is synonymous with the flow of simple liquids such as water. We report the measurement and theoretical verification of non-Newtonian, viscoelastic flow phenomena produced by the high-frequency (20 GHz) vibration of gold nanoparticles immersed in water-glycerol mixtures. The observed viscoelasticity is not due to molecular confinement, but is a bulk continuum effect arising from the short time scale of vibration. This represents the first direct mechanical measurement of the intrinsic viscoelastic properties of simple bulk liquids, and opens a new paradigm for understanding extremely high frequency fluid mechanics, nanoscale sensing technologies, and biophysical processes.
Modeling of Liquid Flow in a Packed Bed in the Presence of Gas Flow
NASA Astrophysics Data System (ADS)
Singh, V.; Gupta, G. S.; Sarkar, S.
2007-06-01
Liquid metal and slag descend through a porous coke matrix in the lower part of an iron making blast furnace. The size of the raceway is an important factor in determining the gas penetration into the bed, which pushes the liquid toward the deadman region. This, in turn, affects the gas flow in the bed. The current study tries to explain theoretically the effect of cavity size hysteresis on gas-liquid distribution in a packed bed. The liquid flow has been modeled considering it to be discrete in nature. The turbulent nature of gas flow has been modeled using the k-ɛ model for turbulent flow. The model results have been verified on a structured package. It is observed that the liquid is pushed away further from the nozzle-side wall in the case of decreasing gas velocity than increasing gas velocity at the same inlet gas velocity. The implications of the current study to the dropping zone of a blast furnace have been discussed.
Progress in Creating Stabilized Gas Layers in Flowing Liquid Mercury
Wendel, Mark W; Felde, David K; Riemer, Bernie; Abdou, Ashraf A; D'Urso, Brian R; West, David L
2009-01-01
The Spallation Neutron Source (SNS) facility in Oak Ridge, Tennessee uses a liquid mercury target that is bombarded with protons to produce a pulsed neutron beam for materials research and development. In order to mitigate expected cavitation damage erosion (CDE) of the containment vessel, a two-phase flow arrangement of the target has been proposed and was earlier proven to be effective in significantly reducing CDE in non-prototypical target bodies. This arrangement involves covering the beam "window", through which the high-energy proton beam passes, with a protective layer of gas. The difficulty lies in establishing a stable gas/liquid interface that is oriented vertically with the window and holds up to the strong buoyancy force and the turbulent mercury flow field. Three approaches to establishing the gas wall have been investigated in isothermal mercury/gas testing on a prototypical geometry and flow: (1) free gas layer approach, (2) porous wall approach, and (3) surface-modified approach. The latter two of these approaches show success in that a stabilized gas layer is produced. Both of these successful approaches capitalize on the high surface energy of liquid mercury by increasing the surface area of the solid wall, thus increasing gas hold up at the wall. In this paper, a summary of these experiments and findings is presented as well as a description of the path forward toward incorporating the stabilized gas layer approach into a feasible gas/mercury SNS target design.
McGrail, Bernard P.; Martin, Paul F.; Lindenmeier, Clark W.
1999-01-01
The present invention is a method and apparatus for measuring coupled flow, transport and reaction processes under liquid unsaturated flow conditions. The method and apparatus of the present invention permit distinguishing individual precipitation events and their effect on dissolution behavior isolated to the specific event. The present invention is especially useful for dynamically measuring hydraulic parameters when a chemical reaction occurs between a particulate material and either liquid or gas (e.g. air) or both, causing precipitation that changes the pore structure of the test material.
Pálfy, Tamás Gábor; Gribovszki, Zoltán; Langergraber, Günter
2015-01-01
The 4,000 PE (700 m(3)/d) wastewater treatment plant at Balf, Hungary was based on sequencing batch reactor technology with phosphorus precipitation as the tertiary step. Its effluent met quality thresholds on average, with above-threshold peaks mainly in winter. The HYDRUS/CW2D model package (PC Progress s.r.o.) was used to simulate the treatment performance of a horizontal flow constructed wetland for polishing effluent. The goal of this study was to provide design-supportive information about the suitability of the proposed wetland and to prove the applicability of the computational tool used to gain that information. The simulations showed that the wetland with the proposed layout could not tackle peaks in NH4-N. Other effluent thresholds could be met, including chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total nitrogen, total inorganic nitrogen and total phosphorus. The tool was unable to simulate COD and BOD5 removal in periods when the electron acceptors were depleted because anaerobic processes are not modelled. Using a tool of such complexity for designing carries excessive work demands and involves many uncertainties. The simulation study highlighted that the model used could still facilitate the design of an effective system by showing the weaknesses of a test scenario as it was demonstrated. PMID:25860697
Hodgdon, M.L.; Oona, H.; Martinez, A.R.; Salon, S.; Wendling, P.; Krahenbuhl, L.; Nicolas, A.; Nicolas, L.
1989-01-01
We present herein the results of three electromagnetic field problems for compressed magnetic field generators and their associated power flow channels. The first problem is the computation of the transient magnetic field in a two-dimensional model of helical generator during loading. The second problem is the three-dimensional eddy current patterns in a section of an armature beneath a bifurcation point of a helical winding. Our third problem is the calculation of the three-dimensional electrostatic fields in a region known as the post-hole convolute in which a rod connects the inner and outer walls of a system of three concentric cylinders through a hole in the middle cylinder. While analytic solutions exist for many electromagnetic field problems in cases of special and ideal geometries, the solutions of these and similar problems for the proper analysis and design of compressed magnetic field generators and their related hardware require computer simulations. In earlier studies, computer models have been proposed, several based on research oriented hydrocodes to which uncoupled or partially coupled Maxwell's equations solvers are added. Although the hydrocode models address the problem of moving, deformable conductors, they are not useful for electromagnetic analysis, nor can they be considered design tools. For our studies, we take advantage of the commercial, electromagnetic computer-aided design software packages FLUX2D nd PHI3D that were developed for motor manufacturers and utilities industries. 4 refs., 6 figs.
NASA Astrophysics Data System (ADS)
Salah, Nebya; Allano, Daniel; Godard, Gilles; Malek, Mokrane; Lebrun, Denis; Paranthoën, P.
2006-09-01
Digital In-line Holography is widely used to visualize fluid flows seeded with small particles. Such holograms record directly the far-field diffraction patterns of particles on a CCD camera. From the successive reconstruction planes, the three-dimensional location of the particles can be determined. This imaging system doesn't need focusing. The principle is based on the direct analysis of the diffraction patterns by mean of space-frequency operators such as Wavelet Transformation or Fractional Fourier Transformation. This method, already tested in our laboratory, leads to a better resolution than classical holography for the estimation of 3D particle locations (50μm instead of 0.5mm in depth). In the case of moving particles, it is interesting to illuminate the sample volume by several laser pulses. This can be easily realized by controlling the input current of a modulated laser diode. Then, the CCD camera cumulates the sum of in-line particle holograms recorded at different times. By searching for the best focus plane of each particle image, the 3D coordinate of each particle can be extracted at a given time. This technique is applied to determine trajectories of small particles in a well-controlled 2D Benard-von Karman street allowing a Lagrangian approach. Preliminary results are presented.
Annular Flow Liquid Film Dynamics in Pipes and Bod Bundle
NASA Astrophysics Data System (ADS)
Ju, Peng
Average liquid film thickness is important for detailed mechanistic modeling of annular two-phase flow in engineering applications. The existing models and correlations either have large relative errors or narrow application range. Because of this, a new liquid film thickness model has been developed for vertical annular flow in pipes based on three databases. The model includes the pressure, liquid and gas velocities, diameter, and viscosity effects on liquid film thickness. Analysis indicates the film thickness to be a function of Weber numbers for both liquid and gas, and the viscosity number. The model is compared with film thickness data which considers a wide range of liquid and gas superficial velocities, system pressure, fluid properties, as well as several pipe diameters. The trend in the current and available film thickness models at various system conditions are analyzed, highlighting the improvement and widening applicability of the new model. The newly proposed film thickness model results in an average relative error of 14% considering the complete database. Interfacial friction factor in annular two-phase flow is essential both for detailed modeling of two-fluid model and the calculation of pressure gradient. Most of the existing correlations on interfacial friction factor are based on Wallis 1969's correlation, which considers the interfacial friction factor as a function of film thickness. In this research, a new correlation of interfacial friction factor that is based on the wave characteristics has been proposed. The wave characteristics is considered to be a function of a group of non-dimensional numbers. Since the effects of wave characteristics for ripples waves and disturbance waves on interfacial friction factors are different, the correlation is divided into two sub-correlations based on these two wave regimes. The new correlation has been compared with a wide range of data. From the data comparison, the new correlation shows significant
Flow characteristics of a partially submerged liquid pickup. Final report
Bartz D.
1984-02-17
Biphase Energy Systems has been developing the technology for two-phase power production. The Biphase turbine is a state-of-the-art two-phase turbine with many potential advantages, including low cost, high efficiency, high torque, and simplicity: The potential exists for substantial performance improvements. This report concludes the third phase of a three-part program funded by the DOE to study energy transfer processes associated with two-phase turbine operation. Figure I-1 shows a schematic of the impulse version of the two-phase turbine. A liquid-gas mixture enters the turbine through the inlet two-phase nozzle. The first energy transfer process occurs here where the mixture expands through the nozzle, converting pressure and thermal energy into flow kinetic energy at the nozzle discharge. Phase I of the progeam determined experimentally the efficiency of the nozzle expansion process. The two-phase jets departing the nozzles impinge on the inner surface of a rotating separator. Here the flow exerts a torque on the separator, which may be used as a drag turbine to convert the flow's kinetic energy into mechanical shaft power. A measure of the momentum transfer from the nozzle exit jet to the rotary separator, defined as torque ratio, was determined. Alternatively, the liquid in the separator may be collected by a stationary diffuser. In this case the liquid kinetic energy is converted to pressure energy by means of momentum diffusion as the flow velocity decreases in a diverging section of diffuser. Phase III of the program examines the characteristics of these enegy conversion processes. In particular, mechanical energy losses associated with external drag, after body wake and spray, and the internal flow losses are predicted and measured.
NASA Astrophysics Data System (ADS)
Kharlamov, S. M.; Guzanov, V. V.; Bobylev, A. V.; Alekseenko, S. V.; Markovich, D. M.
2015-11-01
This article presents the results of experimental investigations of the process of transition from two-dimensional (2D) to three-dimensional (3D) waves in liquid films falling down a vertical plate. The method of laser induced fluorescence was used to obtain instant shapes of three dimensional waves and to investigate the regularities of formation of 3D wave patterns arising due to transverse instability of 2D waves. The obtained results were compared to the results from the published literature on the modeling of 3D wave regimes of film flow. Although many details of 3D wave patterns correspond well, there are a few significant distinctions between our experiments and modeling. In particular, during 2D-3D wave transition, we observed a strong transverse redistribution of liquid leading to the formation of rivulets on the surface of isothermal liquid film, which is a phenomenon not described previously. Possible discrepancies between modeling and experiments, including applicability of boundary layer models and downstream periodic boundary conditions, are discussed. The authors hope that the results presented in the article are of interest not only for modeling of film flows but also for practical applications because at large distances from the film inlet due to 2D-3D wave transition the local flow rates can differ several times at the transverse distances of about 1 cm, which is an effect that cannot be neglected.
Liquid Droplet Detachment and Entrainment in Microscale Flows
NASA Astrophysics Data System (ADS)
Hidrovo, Carlos
2005-11-01
In this talk we will present a first order study of liquid water detachment and entrainment into air flows in hydrophobic microchannels. Silicon based microstructures consisting of 23 mm long U-shaped channels of different geometry were used for this purpose. The structures are treated with a Molecular Vapor Deposition (MVD) process that renders them hydrophobic. Liquid water is injected through a side slot located 2/3 of the way downstream from the air channel inlet. The water entering the air channel beads up into slugs or droplets that grow in size at this injection location until they fill and flood the channel or are carried away by the air flow. The slugs/droplets dimensions at detachment are correlated against superficial gas velocity and proper dimensionless parameters are postulated and examined to compare hydrodynamic forces against surface tension. It is found that slug/droplet detachment is dominated by two main forces: pressure gradient drag, arising from confinement of a viscous flow in the channel, and inertial drag, arising from the stagnation of the air due to obstruction by the slugs/droplets. A detachment regime map is postulated based on the relative importance of these forces under different flow conditions.
Impact of droplets on inclined flowing liquid films.
Che, Zhizhao; Deygas, Amandine; Matar, Omar K
2015-08-01
The impact of droplets on an inclined falling liquid film is studied experimentally using high-speed imaging. The falling film is created on a flat substrate with controllable thicknesses and flow rates. Droplets with different sizes and speeds are used to study the impact process under various Ohnesorge and Weber numbers, and film Reynolds numbers. A number of phenomena associated with droplet impact are identified and analyzed, such as bouncing, partial coalescence, total coalescence, and splashing. The effects of droplet size, speed, as well the film flow rate are studied culminating in the generation of an impact regime map. The analysis of the lubrication force acted on the droplet via the gas layer shows that a higher flow rate in the liquid film produces a larger lubrication force, slows down the drainage process, and increases the probability of droplet bouncing. Our results demonstrate that the flowing film has a profound effect on the droplet impact process and associated phenomena, which are markedly more complex than those accompanying impact on initially quiescent films. PMID:26382528
The Three-D Flow Structures of Gas and Liquid Generated by a Spreading Flame Over Liquid Fuel
NASA Technical Reports Server (NTRS)
Tashtoush, G.; Ito, A.; Konishi, T.; Narumi, A.; Saito, K.; Cremers, C. J.
1999-01-01
We developed a new experimental technique called: Combined laser sheet particle tracking (LSPT) and laser holographic interferometry (HI), which is capable of measuring the transient behavior of three dimensional structures of temperature and flow both in liquid and gas phases. We applied this technique to a pulsating flame spread over n-butanol. We found a twin vortex flow both on the liquid surface and deep in the liquid a few mm below the surface and a twin vortex flow in the gas phase. The first twin vortex flow at the liquid surface was observed previously by NASA Lewis researchers, while the last two observations are new. These observations revealed that the convective flow structure ahead of the flame leading edge is three dimensional in nature and the pulsating spread is controlled by the convective flow of both liquid and gas.
Comaskey, Brian J.; Ault, Earl R.; Kuklo, Thomas C.
2005-07-05
A high average power, low optical distortion laser gain media is based on a flowing liquid media. A diode laser pumping device with tailored irradiance excites the laser active atom, ion or molecule within the liquid media. A laser active component of the liquid media exhibits energy storage times longer than or comparable to the thermal optical response time of the liquid. A circulation system that provides a closed loop for mixing and circulating the lasing liquid into and out of the optical cavity includes a pump, a diffuser, and a heat exchanger. A liquid flow gain cell includes flow straighteners and flow channel compression.
A handy liquid metal based electroosmotic flow pump.
Gao, Meng; Gui, Lin
2014-06-01
A room temperature liquid metal based electroosmotic flow (EOF) pump has been proposed in this work. This low-cost EOF pump is convenient for both fabrication and integration. It utilizes polydimethylsiloxane (PDMS) microchannels filled with the liquid-metal as non-contact pump electrodes. The electrode channels are fabricated symmetrically to both sides of the pumping channel, having no contact with the pumping channel. To test the pumping performance of the EOF pump, the mean flow velocities of the fluid (DI water) in the EOF pumps were experimentally measured by tracing the fluorescent microparticles in the flow. To provide guidance for designing a low voltage EOF pump, parametric studies on dimensions of the electrode and pumping channels were performed in this work. According to the experimental results, the pumping speed can reach 5.93 μm s(-1) at a driving voltage of only 1.6 V, when the gap between the electrode and the pumping channel is 20 μm. Injecting a room temperature liquid metal into microchannels can provide a simple, rapid, low-cost but accurately self-aligned way to fabricate microelectrodes for EOF pumps, which is a promising method to achieve the miniaturization and integration of the EOF pump in microfluidic systems. The non-contact liquid electrodes have no influence on the fluid in the pumping channel when pumping, reducing Joule heat generation and preventing gas bubble formation at the surface of electrodes. The pump has great potential to drive a wide range of fluids, such as drug reagents, cell suspensions and biological macromolecule solutions. PMID:24706096
Convection flows driven by laser heating of a liquid layer
NASA Astrophysics Data System (ADS)
Rivière, David; Selva, Bertrand; Chraibi, Hamza; Delabre, Ulysse; Delville, Jean-Pierre
2016-02-01
When a fluid is heated by the absorption of a continuous laser wave, the fluid density decreases in the heated area. This induces a pressure gradient that generates internal motion of the fluid. Due to mass conservation, convection eddies emerge in the sample. To investigate these laser-driven bulk flows at the microscopic scale, we built a setup to perform temperature measurements with a fluorescent-sensitive dye on the one hand, and measured the flow pattern at different beam powers, using a particle image velocimetry technique on the other hand. Temperature measurements were also used in numerical simulations in order to compare predictions to the experimental velocity profiles. The combination of our numerical and experimental approaches allows a detailed description of the convection flows induced by the absorption of light, which reveals a transition between a thin and a thick liquid layer regime. This supports the basis of optothermal approaches for microfluidic applications.
NASA Astrophysics Data System (ADS)
Moura, Marcel; Fiorentino, Eve-Agnès; Jørgen Måløy, Knut; Toussaint, Renaud; Schäfer, Gerhard
2015-04-01
We have performed two-phase flow experiments to analyze the drainage from a quasi-2D random porous medium. The medium is transparent, which allows for the visualization of the invasion pattern during the flow and is initially fully saturated with a viscous fluid (a dyed glycerol-water mix). As the pressure in the fluid is gradually reduced, air penetrates from an open inlet, thus displacing the fluid which leaves the system from the outlet in the opposite side. A feedback mechanism was devised to control the experiment: the capillary pressure (difference in pressure between the non-wetting and wetting phases) is continuously increased to be just above the threshold value necessary to drive the invasion process. This mechanism is intended to keep the invasion process slow, in the so-called capillary regime, where capillary forces dominate the dynamics. Pressure measurements and pictures of the flow are recorded and the pressure-saturation relationship is computed. The effects of the boundary conditions to this quantity are verified experimentally by repeatedly performing the analysis using porous media of different sizes. We show that some features of the pressure-saturation curve are strongly affected by boundary effects. The invasion close to the inlet and outlet of the model are particularly influenced by the boundaries and this is reflected in the phases of pressure building up in the pressure-saturation curves, in the beginning and end of the invasion process. Conversely, at the central part of the model (away from the boundaries), the invasion process happens at an essentially constant capillary pressure, which is reflected as a plateau in the pressure-saturation curve. Additionally, the use of a high-resolution camera allows us to analyze the images down to the pore scale. We can directly obtain a distribution of pore-throat sizes in the model (and their associated capillary pressure thresholds) and divide it into distributions of invaded / non-invaded pores
Tschäppät, Viviane; Varesio, Emmanuel; Signor, Luca; Hopfgartner, Gérard
2005-09-01
2-D nanoscale LC combined with a triple quadrupole-linear ion trap mass spectrometer was applied to the analysis of a complex peptide mixture. A 2-D dual nanoscale LC-MS/MS system was compared to a conventional one. Peptides were separated with a strong cation exchange (SCX) microcolumn in the first dimension and two C18 nanocolumns were used as second dimension. MS experiments were performed using information-dependent data acquisition, where two precursor ions were selected from an enhanced MS (EMS) or an enhanced multicharged ion (EMC) as survey scan. The major benefit of EMC instead of EMS was a two-fold reduction of the data file and a 15% increase of characterized proteins. The advantage of the 2-D dual nanoscale LC-MS/MS system versus the conventional 2-D nanoscale LC-MS/MS system was reflected in the significant increase of peptides which were successfully identified within the same time frame. The first factor contributing to this increase was that the mass spectrometer was collecting twice the number of relevant MS/MS data. The second factor is the use of twice the number of SCX salt fractions in the first dimension, allowing a better sample fractionation, thereby reducing the number of peptides transferred to the second chromatographic dimension per salt fraction. PMID:16224964
Bubble Generation in a Flowing Liquid Medium and Resulting Two-Phase Flow in Microgravity
NASA Technical Reports Server (NTRS)
Pais, S. C.; Kamotani, Y.; Bhunia, A.; Ostrach, S.
1999-01-01
The present investigation reports a study of bubble generation under reduced gravity conditions, using both a co-flow and a cross-flow configuration. This study may be used in the conceptual design of a space-based thermal management system. Ensuing two-phase flow void fraction can be accurately monitored using a single nozzle gas injection system within a continuous liquid flow conduit, as utilized in the present investigation. Accurate monitoring of void fraction leads to precise control of heat and mass transfer coefficients related to a thermal management system; hence providing an efficient and highly effective means of removing heat aboard spacecraft or space stations. Our experiments are performed in parabolic flight aboard the modified DC-9 Reduced Gravity Research Aircraft at NASA Lewis Research Center, using an air-water system. For the purpose of bubble dispersion in a flowing liquid, we use both a co-flow and a cross-flow configuration. In the co-flow geometry, air is introduced through a nozzle in the same direction with the liquid flow. On the other hand, in the cross-flow configuration, air is injected perpendicular to the direction of water flow, via a nozzle protruding inside the two-phase flow conduit. Three different flow conduit (pipe) diameters are used, namely, 1.27 cm, 1.9 cm and 2.54 cm. Two different ratios of nozzle to pipe diameter (D(sub N))sup * are considered, namely (D(sub N))sup * = 0.1 and 0.2, while superficial liquid velocities are varied from 8 to 70 cm/s depending on flow conduit diameter. It is experimentally observed that by holding all other flow conditions and geometry constant, generated bubbles decrease in size with increase in superficial liquid velocity. Detached bubble diameter is shown to increase with air injection nozzle diameter. Likewise, generated bubbles grow in size with increasing pipe diameter. Along the same lines, it is shown that bubble frequency of formation increases and hence the time to detachment of a
Intermittency of rheological regimes in uniform liquid-granular flows.
Armanini, Aronne; Larcher, Michele; Fraccarollo, Luigi
2009-05-01
We present a detailed analysis of a free surface-saturated liquid-granular mixture flowing over a static loose bed of grains, where the coexistence of layers dominated by collisional and frictional interactions among particles was observed. Kinetic theory was applied to the flow described above and it proved suitable for describing a realistic behavior of the collisional layers, although it failed to interpret the regions of the flow domain dominated by the frictional contacts. The paper provides a conceptual scheme with which to overcome this problem by focusing on the mechanisms governing the transition from the frictional to the collisional regime. In particular we observed that in highly concentrated flows the transition layer exhibits a typical intermittency of the dominating rheological regime, switching alternately from the frictional to the collisional one. By filtering the velocity signal, we introduced an intermittency function that made it possible to extend the validity of the equations derived from dense gas analogy, typical of the collisional regimes, also in the intermittent phase of the flow. Owing to the small values of the Stokes number, in the application of the kinetic theory we accounted for the possible variation of the elastic restitution coefficient along the flow depth. PMID:19518448
Gas and liquid measurements in air-water bubbly flows
Zhou, X.; Doup, B.; Sun, X.
2012-07-01
Local measurements of gas- and liquid-phase flow parameters are conducted in an air-water two-phase flow loop. The test section is a vertical pipe with an inner diameter of 50 mm and a height of 3.2 m. The measurements are performed at z/D = 10. The gas-phase measurements are performed using a four-sensor conductivity probe. The data taken from this probe are processed using a signal processing program to yield radial profiles of the void fraction, bubble velocity, and interfacial area concentration. The velocity measurements of the liquid-phase are performed using a state-of-the-art Particle Image Velocimetry (PIV) system. The raw PIV images are acquired using fluorescent particles and an optical filtration device. Image processing is used to remove noise in the raw PIV images. The statistical cross correlation is introduced to determine the axial velocity field and turbulence intensity of the liquid-phase. Measurements are currently being performed at z/D = 32 to provide a more complete data set. These data can be used for computational fluid dynamic model development and validation. (authors)
Guo, Shuang; Zhu, Chenqi; Gao-Yang, Yaya; Qiu, Bailing; Wu, Di; Liang, Qihui; He, Jiayuan; Han, Nanyin
2016-02-01
Gravitational field-flow fractionation is the simplest field-flow fractionation technique in terms of principle and operation. The earth' s gravity is its external field. Different sized particles are injected into a thin channel and carried by carrier fluid. The different velocities of the carrier liquid in different places results in a size-based separation. A gravitational field-flow fractionation (GrFFF) instrument was designed and constructed. Two kinds of polystyrene (PS) particles with different sizes (20 µm and 6 µm) were chosen as model particles. In this work, the separation of the sample was achieved by changing the concentration of NaN3, the percentage of mixed surfactant in the carrier liquid and the flow rate of carrier liquid. Six levels were set for each factor. The effects of these three factors on the retention ratio (R) and plate height (H) of the PS particles were investigated. It was found that R increased and H decreased with increasing particle size. On the other hand, the R and H increased with increasing flow rate. The R and H also increased with increasing NaN3 concentration. The reason was that the electrostatic repulsive force between the particles and the glass channel wall increased. The force allowed the samples approach closer to the channel wall. The results showed that the resolution and retention time can be improved by adjusting the experimental conditions. These results can provide important values to the further applications of GrFFF technique. PMID:27382718
Effect of Energetic Plasma Flux on Flowing Liquid Lithium Surfaces
NASA Astrophysics Data System (ADS)
Kalathiparambil, Kishor; Jung, Soonwook; Christenson, Michael; Fiflis, Peter; Xu, Wenyu; Szott, Mathew; Ruzic, David
2014-10-01
An operational liquid lithium system with steady state flow driven by thermo-electric magneto-hydrodynamic force and capable of constantly refreshing the plasma exposed surface have been demonstrated at U of I. To evaluate the system performance in reactor relevant conditions, specifically to understand the effect of disruptive plasma events on the performance of the liquid metal PFCs, the setup was integrated to a pulsed plasma generator. A coaxial plasma generator drives the plasma towards a theta pinch which preferentially heats the ions, simulating ELM like flux, and the plasma is further guided towards the target chamber which houses the flowing lithium system. The effect of the incident flux is examined using diagnostic tools including triple Langmuir probe, calorimeter, rogowski coils, Ion energy analyzers, and fast frame spectral image acquisition with specific optical filters. The plasma have been well characterized and a density of ~1021 m-3, with electron temperature ~10 - 20 eV is measured, and final plasma velocities of 34 - 74 kms-1 have been observed. Calorimetric measurements using planar molybdenum targets indicate a maximum plasma energy (with 6 kV plasma gun and 20 kV theta pinch) of 0.08 MJm-2 with plasma divergence effects resulting in marginal reduction of 40 +/- 23 J in plasma energy. Further results from the other diagnostic tools, using the flowing lithium targets and the planar targets coated with lithium will be presented. DOE DE-SC0008587.
Mechanical annealing in the flow of supercooled metallic liquid
Zhang, Meng; Dai, Lan Hong; Liu, Lin
2014-08-07
Flow induced structural evolution in a supercooled metallic liquid Vit106a (Zr{sub 58.5}Cu{sub 15.6}Al{sub 10.3}Ni{sub 12.8}Nb{sub 2.8}, at. %) was investigated via uni-axial compression combined with differential scanning calorimeter (DSC). Compression tests at strain rates covering the transition from Newtonian flow to non-Newtonian flow and at the same strain rate 2 × 10{sup −1} s{sup −1} to different strains were performed at the end of glass transition (T{sub g-end} = 703 K). The relaxation enthalpies measured by DSC indicate that the samples underwent non-Newtonian flow contain more free volume than the thermally annealed sample (703 K, 4 min), while the samples underwent Newtonian flow contain less, namely, the free volume of supercooled metallic liquids increases in non-Newtonian flow, while decreases in Newtonian flow. The oscillated variation of the relaxation enthalpies of the samples deformed at the same strain rate 2 × 10{sup −1} s{sup −1} to different strains confirms that the decrease of free volume was caused by flow stress, i.e., “mechanical annealing.” Micro-hardness tests were also performed to show a similar structural evolution tendency. Based on the obtained results, the stress-temperature scaling in the glass transition of metallic glasses are supported experimentally, as stress plays a role similar to temperature in the creation and annihilation of free volume. In addition, a widening perspective angle on the glass transition of metallic glasses by exploring the 3-dimensional stress-temperature-enthalpy phase diagram is presented. The implications of the observed mechanical annealing effect on the amorphous structure and the work-hardening mechanism of metallic glasses are elucidated based on atomic level stress model.
Visualization of diffuser outlet flow using liquid crystal sheets
Kirkpatrick, A.T.
1995-08-01
This article describes a new imaging technique to determine air temperatures and flow fields from HVAC diffusers. The technique uses liquid crystal sheets to record the airflow and temperatures in color. The air temperature field is an important contributor to the thermal comfort in a room and is used to evaluate diffuser performance. Visualization of the temperature field allows one to see directly the flow field and how it is interacting with the room air. a particular application is to cold-air distribution systems that supply cooling and ventilation air to rooms at temperatures lower than in conventional systems. In these systems the cold-air supply is as low as 39 F (4 C), instead of the conventional value of 55 F (13 C). This new technique uses a temperature-sensitive liquid crystal sheet to create a visual measuring tool. The liquid crystals are layered on a plane sheet and produce two-dimensional color images of the air temperature field. Since air is invisible, some type of indicator placed in the air stream is required to determine the air temperature. At present, instruments such as thermocouples and thermistors determine the air temperature in rooms and measure the value at a single point. Information about the temperature and flow field in a room is obtained by moving the device, or using multiple sensors. This is a time-consuming process, and only yields information at the points of measurement. However, the temperature field is usually unsteady, due to variable air currents and cooling loads, so a movable device is not entirely suitable, and multiple instruments require multiple data acquisition channels. It would be more informative to visualize the entire airflow from the diffuser at any instant. This article deals with a temperature characterization method.
Optimizing the flow in a liquid sodium dynamo experiment
NASA Astrophysics Data System (ADS)
Taylor, N. Zane
The Madison Dynamo experiment drives a turbulent flow of liquid sodium in a sphere in order to observe a MHD dynamo instability: An exponentially growing magnetic field at the expense of kinetic energy. Initial runs of the experiment observed intermittent bursts of the predicted magnetic mode, but no self-excited field was observed. It was found that turbulent fluctuations were producing large-scale magnetic fields that were a significant fraction of the magnitude of the fields induced by the mean flow. These turbulent-induced fields were solely detrimental, opposing the generation of the magnetic field produced by the mean flow. Baffles and vanes were added to the experiment to optimize the helical pitch of the mean flow and to remove the large-scale detrimental fluctuations. The observed drop in required motor power and a drop in specific measured magnetic response modes gives direct confirmation that these large detrimental eddies have been removed. A probe was developed to characterize the turbulence in the MDE after the baffles were installed and it was determined that the remaining turbulent EMF was mostly acting as an enhanced dissipation to the induced magnetic field. After these modifications, the induced magnetic field produced by the flowing sodium interacting with a seed magnetic field now closely matches laminar predictions. However, no self-excited field has been observed. A velocity inversion technique has been developed that compares internal and external field measurements with a predictive model and determines what the effective mean flow is in the experiment. Results from this velocity inversion give another metric on how optimized the flow profile is and also provide the most robust method of determining how close the experiment is to achieving a dynamo.
Instability of flow of liquid film over a heated surface
Sha, W.T.; Soo, S.L.
1994-08-01
Fundamental concepts and basic equations of a flowing thin liquid film cooling a heated surfaced by its vaporization and the effect of dry patches were treated. Stable film flow prior to the appearance of dry patches on the heated surface is maintained by a balance of various forces due to surface tension, shear stress, heat and mass transfer, and gravity. Film splitting at a critical film thickness produces dry patches due to perturbation by waves on a perfect surface, and often by surface imperfection and uneven heating. This work is primarily motivated by the design of next-generation nuclear reactors, which employ many novel passive heat-removal systems via natural circulation. These systems are design to prevent damage to the reactor core and containment without action by the reactor operators during or after a design basis accident such as a loss of coolant accident (LOCA) or a main steam-line break (MSLB) accident.
Characterization of annular two-phase gas-liquid flows in microgravity
NASA Technical Reports Server (NTRS)
Bousman, W. Scott; Mcquillen, John B.
1994-01-01
A series of two-phase gas-liquid flow experiments were developed to study annular flows in microgravity using the NASA Lewis Learjet. A test section was built to measure the liquid film thickness around the perimeter of the tube permitting the three dimensional nature of the gas-liquid interface to be observed. A second test section was used to measure the film thickness, pressure drop and wall shear stress in annular microgravity two-phase flows. Three liquids were studied to determine the effects of liquid viscosity and surface tension. The result of this study provide insight into the wave characteristics, pressure drop and droplet entrainment in microgravity annular flows.
Pinch off and reconnection in liquid/liquid flows: joint experimental and numerical studies
Ellen K. Longmire; John S. Lowengrub
2005-09-26
Liquid/liquid systems appear in applications involving transport, mixing, and separation of petroleum, chemical, and waste products. Breakup and coalescence transitions often determine flow regimes as well as reaction and separation rates. Because they occur over very small time and length scales compared with the larger scales that dominate the flow, they are difficult to quantify experimentally and simulate numerically. Thus far, no accurate models exist for engineers to predict these flows. Experiments and computations were performed so that accurate engineering models can be developed. Jet pinch off and drop coalescence were examined in mixtures of water/glycerin and silicone oil. Index matching, laser sheet illumination, and the PIV method were applied to obtain visualization and velocity field sequences through transitions. The computations used a novel, physically-based method that captures interface breakup and coalescence automatically without resorting to ad-hoc cut-and-connect methods. To achieve enhanced accuracy near transitions, new adaptive time and space meshes were developed. The computations were validated through direct comparison with the experiments. The detailed results should lead to improved understanding of transition behavior. This understanding is needed to develop engineering models of multiphase flows. Such predictive models will lead to extensive cost savings in device and process design.
Marangoni instability of a liquid film flow with viscous dissipation.
Celli, Michele; Barletta, Antonio; Alves, Leonardo S de B
2015-02-01
A linear stability analysis of a thin liquid film flowing over a plate is performed. The plate is considered as impermeable and adiabatic. The upper surface of the film is assumed to be a free boundary with a non-negligible surface tension, characterized by a Robin thermal boundary condition. The thermoconvective instability is generated by the interplay between the heating due to viscous dissipation and the temperature-dependent surface tension at the free boundary. A basic parallel flow, arbitrarily oriented, is assumed and the basic temperature profile is determined analytically. In order to investigate the linear stability of the system, the normal mode method is employed. A system of ordinary differential equations defining an eigenvalue problem is thus obtained. The case of longitudinal rolls, where the base flow velocity is parallel to the axis rolls, is solved both analytically and numerically. Other possible inclinations of the base flow are investigated by means of a numerical procedure based on combining the Runge-Kutta and the shooting methods. PMID:25768596
Marangoni instability of a liquid film flow with viscous dissipation
NASA Astrophysics Data System (ADS)
Celli, Michele; Barletta, Antonio; Alves, Leonardo S. de B.
2015-02-01
A linear stability analysis of a thin liquid film flowing over a plate is performed. The plate is considered as impermeable and adiabatic. The upper surface of the film is assumed to be a free boundary with a non-negligible surface tension, characterized by a Robin thermal boundary condition. The thermoconvective instability is generated by the interplay between the heating due to viscous dissipation and the temperature-dependent surface tension at the free boundary. A basic parallel flow, arbitrarily oriented, is assumed and the basic temperature profile is determined analytically. In order to investigate the linear stability of the system, the normal mode method is employed. A system of ordinary differential equations defining an eigenvalue problem is thus obtained. The case of longitudinal rolls, where the base flow velocity is parallel to the axis rolls, is solved both analytically and numerically. Other possible inclinations of the base flow are investigated by means of a numerical procedure based on combining the Runge-Kutta and the shooting methods.
Flowing Foam: T1 events and solid-liquid transitions.
NASA Astrophysics Data System (ADS)
Dennin, Michael
2005-11-01
Flowing aqueous foam is found in many applications ranging from oil recovery, to fire fighting, to spreading shaving cream. Aqueous foam consists of gas bubbles with liquid walls. One of the striking features of foam is that despite being composed entirely of fluids, its mechanical properties are either those of a solid (elastic response) or fluid (viscous flow), depending on the nature of the applied stress and strains. We study the transition between these two regimes using a model foam system: bubble rafts. Bubble rafts are a single layer of bubbles floating on the air-water surface. This allows us to track the motion of all the bubbles during flow. In this talk, we will present two main results. First, we will discuss the observation of the coexistence between a solid-like and fluid-like state during flow. Second, we will discuss the role played by nonlinear, topological rearrangements, known as T1 events, in determining the mechanical response of the system.
NASA Astrophysics Data System (ADS)
Torii, Hajime
2012-12-01
A time-domain computational method for calculating 1D and 2D spectra of resonantly-coupled vibrations in condensed-phase systems is presented. This method simultaneously takes into account the diagonal frequency modulations, the off-diagonal vibrational couplings, and the dynamics of the system, and is applicable to systems of wide interest, e.g., the O-H stretching modes of water and alcohols, and the amide I modes of proteins. The case of the amide I mode of (Ala-d)4 in D2O solution is shown as an example.
Measurements of Gas Bubble Size Distributions in Flowing Liquid Mercury
Wendel, Mark W; Riemer, Bernie; Abdou, Ashraf A
2012-01-01
ABSTRACT Pressure waves created in liquid mercury pulsed spallation targets have been shown to induce cavitation damage on the target container. One way to mitigate such damage would be to absorb the pressure pulse energy into a dispersed population of small bubbles, however, measuring such a population in mercury is difficult since it is opaque and the mercury is involved in a turbulent flow. Ultrasonic measurements have been attempted on these types of flows, but the flow noise can interfere with the measurement, and the results are unverifiable and often unrealistic. Recently, a flow loop was built and operated at Oak Ridge National Labarotory to assess the capability of various bubbler designs to deliver an adequate population of bubbles to mitigate cavitation damage. The invented diagnostic technique involves flowing the mercury with entrained gas bubbles in a steady state through a horizontal piping section with a glass-window observation port located on the top. The mercury flow is then suddenly stopped and the bubbles are allowed to settle on the glass due to buoyancy. Using a bright-field illumination and a high-speed camera, the arriving bubbles are detected and counted, and then the images can be processed to determine the bubble populations. After using this technique to collect data on each bubbler, bubble size distributions were built for the purpose of quantifying bubbler performance, allowing the selection of the best bubbler options. This paper presents the novel procedure, photographic technique, sample visual results and some example bubble size distributions. The best bubbler options were subsequently used in proton beam irradiation tests performed at the Los Alamos National Laboratory. The cavitation damage results from the irradiated test plates in contact with the mercury are available for correlation with the bubble populations. The most effective mitigating population can now be designed into prototypical geometries for implementation into
Large Flow-Birefringence of Nematogenic Bent-Core Liquid Crystals
NASA Astrophysics Data System (ADS)
Bailey, Christopher; Fodor-Csorba, Katalin; Verduzco, Rafael; Gleeson, James; Sprunt, Samuel; Jakli, Antal
2009-03-01
We have found that bent-core liquid crystalline materials show exceptionally large flow birefringence in their isotropic liquid phase. The flow birefringence is over two orders of magnitude larger than usual for low molecular weight liquid crystals. Comparing the flow birefringence per unit viscosity, the observed values are an order of magnitude larger than low molecular weight and side-chain polymeric calamitic liquid crystals. This large flow birefringence is attributed to the nanostructure of these materials that contain temporary smectic clusters of a few smectic layers, which exist even in their isotropic phase. These smectic clusters appear to shear align resulting in the observed flow birefringence behavior.
Gravity-driven liquid flow over a flexible beam
NASA Astrophysics Data System (ADS)
Kim, Hyoungsoo; Howell, Peter; Popova, Marinela; Stone, Howard
2015-11-01
We study theoretically and experimentally the time dependence of a liquid spreading along a flexible beam. The flow is modeled using lubrication theory and the substrate is modeled as an (Euler-Bernoulli) elastic beam. We classify the model problem into two cases depending on the maximum beam deflection angle ϕmax from the horizontal, i.e. a small deflection (ϕmax < 30°) and large deflection (30° < ϕmax < 90°). For a small deflection case, we obtain asymptotic solutions for the liquid propagation speed for the early time and terminal time periods, which for the front position σ(t) show power-law behaviors σ(t) ~ t 4 / 5 and σ(t) ~ t4, respectively. The theoretical model also predicts the deflection angle of the beam at the propagating liquid front. We validate the results with experiments, which show good agreement with theory. Furthermore, for large beam deflections, we obtain experimental results demonstrating power-law behaviors, σ(t) ~ t and ϕ(t) ~ t2 for the early time period.
Two-phase, gas-liquid flows in static mixers
Shah, N.F.; Kale, D.D. )
1992-02-01
This paper reports that static mixers are used for many gas-liquid two-phase operations. some of the typical applications are processing of natural gas to remove hydrogen sulfide or carbon dioxide, waste water treatment, dissolution of gases, hydrogenation, chlorination, and so on. They have experimentally studied the pressure drop for oxygen-water system in a bubble column packed with Sulzer-Koch-type mixing elements. They observed that the ratio of pressure drop through the packed bubble column to that through the unpacked one was slightly greater than one. The suitability of static mixers to mix fluids of very widely different viscosities has been demonstrated. Two-phase operations in polymer industry involve very viscous fluids. Due to the high viscosity of these fluids, the flow will be predominantly in laminar region for both fluids. There are no data on gas-liquid two-phase systems incorporating viscous Newtonian and non-Newtonian fluids where flows are predominantly in laminar region.
Stabilising falling liquid film flows using feedback control
NASA Astrophysics Data System (ADS)
Thompson, Alice B.; Gomes, Susana N.; Pavliotis, Grigorios A.; Papageorgiou, Demetrios T.
2016-01-01
Falling liquid films become unstable due to inertial effects when the fluid layer is sufficiently thick or the slope sufficiently steep. This free surface flow of a single fluid layer has industrial applications including coating and heat transfer, which benefit from smooth and wavy interfaces, respectively. Here, we discuss how the dynamics of the system are altered by feedback controls based on observations of the interface height, and supplied to the system via the perpendicular injection and suction of fluid through the wall. In this study, we model the system using both Benney and weighted-residual models that account for the fluid injection through the wall. We find that feedback using injection and suction is a remarkably effective control mechanism: the controls can be used to drive the system towards arbitrary steady states and travelling waves, and the qualitative effects are independent of the details of the flow modelling. Furthermore, we show that the system can still be successfully controlled when the feedback is applied via a set of localised actuators and only a small number of system observations are available, and that this is possible using both static (where the controls are based on only the most recent set of observations) and dynamic (where the controls are based on an approximation of the system which evolves over time) control schemes. This study thus provides a solid theoretical foundation for future experimental realisations of the active feedback control of falling liquid films.
Numerical simulations of high Knudsen number gas flows and microchannel electrokinetic liquid flows
NASA Astrophysics Data System (ADS)
Yan, Fang
Low pressure and microchannel gas flows are characterized by high Knudsen numbers. Liquid flows in microchannels are characterized by non-conventional driving potentials like electrokinetic forces. The main thrust of the dissertation is to investigate these two different kinds of flows in gases and liquids respectively. High Knudsen number (Kn) gas flows were characterized by 'rarified' or 'microscale' behavior. Because of significant non-continuum effect, traditional CFD techniques are often inaccurate for analyzing high Kn number gas flows. The direct simulation Monte Carlo (DSMC) method offers an alternative to traditional CFD which retains its validity in slip and transition flow regimes. To validate the DSMC code, comparisons of simulation results with theoretical analysis and experimental data are made. The DSMC method was first applied to compute low pressure, high Kn flow fields in partially heated two dimensional channels. The effects of varying pressure, inlet flow and gas transport properties (Kn, Reynolds number, Re and the Prandtl number, Pr respectively) on the wall heat transfer (Nusselt number, Nu) were examined. The DSMC method was employed to explore mixing gas flows in two dimensional microchannels. Mixing of two gas streams (H2 and O2) was considered within a microchannel. The effect of the inlet-outlet pressure difference, the pressure ratio of the incoming streams and the accommodation coefficient of the solid wall on mixing length were all examined. Parallelization of a three-dimensional DSMC code was implemented using OpenMP procedure on a shared memory multi-processor computer. The parallel code was used to simulate 3D high Kn number Couette flow and the flow characteristics are found to be very different from their continuum counterparts. A mathematical model describing electrokinetically driven mass transport phenomena in microfabricated chip devices will also be presented. The model accounts for the principal physical phenomena affecting
Kaluza, Dawid; Adamiak, Wojciech; Kalwarczyk, Tomasz; Sozanski, Krzysztof; Opallo, Marcin; Jönsson-Niedziolka, Martin
2013-12-23
We have investigated the oxidation of ferrocene at a flowing organic solvent|aqueous electrolyte|solid electrode junction in a microfluidic setup using cyclic voltammetry and fluorescent laser scanning confocal microscopy. At low flow rates the oxidation current decreases with increasing flow, contrary to the Levich equation, but at higher flow rates the current increases linearly with the cube root of the flow rate. This behavior is explained using a simple model postulating a smallest effective width of the three-phase junction, which after fitting to the data comes to be ca. 20 μm. The fluorescence microscopy reveals mixing of the two phases close to the PDMS cover, but the liquid|liquid junction is stable close to the glass support. This study shows the importance of the solid|liquid|liquid junctions for the behavior of multiphase systems under microfluidic conditions. PMID:24328179
NASA Astrophysics Data System (ADS)
Castro, Maria Clara; Patriarche, Delphine; Goblet, Patrick
2005-09-01
Because helium and heat production results from a common source, a continental 4He crustal flux of 4.65 * 10 - 14 mol m - 2 s - 1 has been estimated based on heat flow considerations. In addition, because the observed mantle He / heat flux ratio at the proximity of mid-ocean ridges (6.6 * 10 - 14 mol J - 1 ) is significantly lower than the radiogenic production ratio (1.5 * 10 - 12 mol J - 1 ), the presence of a terrestrial helium-heat imbalance was suggested. The latter could be explained by the presence of a layered mantle in which removal of He is impeded from the lower mantle [R.K. O'Nions, E.R. Oxburgh, Heat and helium in the Earth, Nature 306 (1983) 429-431; E.R. Oxburgh, R.K. O'Nions, Helium loss, tectonics, and the terrestrial heat budget, Science 237 (1987) 1583-1588]. van Keken et al. [P.E. van Keken, C.J. Ballentine, D. Porcelli, A dynamical investigation of the heat and helium imbalance, Earth Planet, Sci. Lett. 188 (2001) 421-434] have recently claimed that the helium-heat imbalance remains a robust observation. Such conclusions, however, were reached under the assumption that a steady-state regime was in place for both tracers and that their transport properties are similar at least in the upper portion of the crust. Here, through 2-D simulations of groundwater flow, heat transfer and 4He transport carried out simultaneously in the Carrizo aquifer and surrounding formations in southwest Texas, we assess the legitimacy of earlier assumptions. Specifically, we show that the driving transport mechanisms for He and heat are of a fundamentally different nature for a high range of permeabilities ( k ≤ 10 - 16 m 2) found in metamorphic and volcanic rocks at all depths in the crust. The assumption that transport properties for these two tracers are similar in the crust is thus unsound. We also show that total 4He / heat flux ratios lower than radiogenic production ratios do not reflect a He deficit in the crust or mantle original reservoir. Instead, they
NASA Astrophysics Data System (ADS)
Arapov, Yu. G.; Yakunin, M. V.; Gudina, S. V.; Harus, G. I.; Neverov, V. N.; Shelushinina, N. G.; Podgornyh, S. M.; Uskova, E. A.; Zvonkov, B. N.
2007-04-01
The resistivity ρ of low mobility dilute 2D-elecron gas in a InGaAs/GaAs double quantum well (DQW) exhibits the monotonic "insulating-like" temperature dependence (dρ/dT < 0) at T = 1.8-70K in zero magnetic field. This temperature interval corresponds to a ballistic regime (kBTτ/ℏ > 0.1) for our samples. We observed the coexistence of both the quantum Hall (QH) effect for the filling factors v = 2, 4 and the low magnetic field insulator — QH liquid (with v = 10) transition.
NASA Astrophysics Data System (ADS)
Rosenauer, M.; Vellekoop, M. J.
2009-10-01
In this paper we present the design and operation of a micro flow cell comprising a liquid-core/liquid-twin-cladding waveguide for on-chip fluorescence spectroscopy based on evanescent field illumination. The application of an inner (sample) and outer cladding stream minimizes the sample volume for optical measurements and ensures the analyte position in the evanescent field for excitation at the core/cladding interface. The fiber-chip-coupled laser light is guided by the fluidic waveguide providing a uniform excitation along the analysis channel. Fluorescence intensity measurements of different sample solutions were conducted to illustrate the operational quality. The fluidics device is fabricated by laser microstereolithography in 1.5 h.
Light-Driven Transport of a Liquid Marble with and against Surface Flows.
Kavokine, Nikita; Anyfantakis, Manos; Morel, Mathieu; Rudiuk, Sergii; Bickel, Thomas; Baigl, Damien
2016-09-01
Liquid marbles, that is, liquid drops coated by a hydrophobic powder, do not wet any solid or liquid substrate, making their transport and manipulation both highly desirable and challenging. Herein, we describe the light-driven transport of floating liquid marbles and emphasize a surprising motion behavior. Liquid marbles are deposited on a water solution containing photosensitive surfactants. Irradiation of the solution generates photoreversible Marangoni flows that transport the liquid marbles toward UV light and away from blue light when the thickness of the liquid substrate is large enough (Marangoni regime). Below a critical thickness, the liquid marbles move in the opposite direction to that of the surface flow at a speed increasing with decreasing liquid thickness (anti-Marangoni). We demonstrate that the anti-Marangoni motion is driven by the free surface deformation, which propels the non-wetting marble against the surface flow. We call this behavior "slide effect". PMID:27381297
NASA Technical Reports Server (NTRS)
Thompson, David S.; Soni, Bharat K.
2000-01-01
An integrated software package, ICEG2D, was developed to automate computational fluid dynamics (CFD) simulations for single-element airfoils with ice accretion. ICEG2D is designed to automatically perform three primary functions: (1) generating a grid-ready, surface definition based on the geometrical characteristics of the iced airfoil surface, (2) generating a high-quality grid using the generated surface point distribution, and (3) generating the input and restart files needed to run the general purpose CFD solver NPARC. ICEG2D can be executed in batch mode using a script file or in an interactive mode by entering directives from a command line. This report summarizes activities completed in the first year of a three-year research and development program to address issues related to CFD simulations for aircraft components with ice accretion. Specifically, this document describes the technology employed in the software, the installation procedure, and a description of the operation of the software package. Validation of the geometry and grid generation modules of ICEG2D is also discussed.
Eyler, L.L.; Budden, M.J.
1985-03-01
The objective of this work is to assess prediction capabilities and features of the MAGNUM-2D computer code in relation to its intended use in the Basalt Waste Isolation Project (BWIP). This objective is accomplished through a code verification and benchmarking task. Results are documented which support correctness of prediction capabilities in areas of intended model application. 10 references, 43 figures, 11 tables.
Digal, Sanatan; Ray, Rajarshi; Saumia, P S; Srivastava, Ajit M
2013-10-01
We analyze the dynamics of dark brushes connecting point vortices of strength ±1 formed in the isotropic-nematic phase transition of a thin layer of nematic liquid crystals, using a crossed polarizer set up. The evolution of the brushes is seen to be remarkably similar to the evolution of line defects in a three-dimensional nematic liquid crystal system. Even phenomena like the intercommutativity of strings are routinely observed in the dynamics of brushes. We test the hypothesis of a duality between the two systems by determining exponents for the coarsening of total brush length with time as well as shrinking of the size of an isolated loop. Our results show scaling behavior for the brush length as well as the loop size with corresponding exponents in good agreement with the 3D case of string defects. PMID:24026004
NASA Astrophysics Data System (ADS)
Baudon, Catherine; Gillet, Hervé; Cremer, Michel
2013-04-01
High-quality bathymetric, 2D seismic and Chirp data located in the southern parts of the Bay of Biscay, France, collected by the University of Bordeaux 1 (Cruises ITSAS 2, 2001; PROSECAN 3, 2006 and SARGASS, 2010) have recently been compiled. The survey area widely covers the Capbreton Canyon, which lies on the boundary between two major structural zones: the Aquitanian passive margin to the North, and the Basque-Cantabrian margin to the South which corresponds to the offshore Pyrenean front. The dataset revealed a large number of key seafloor features potentially associated with focused fluid-flow processes and subsurface sediment-remobilization. Focused fluid migration through sub-seabed sediments is a common phenomenon on continental margins worldwide and has widespread implications from both industrial and fundamental perspectives, from seafloor marine environmental issues to petroleum exploration and hazard assessments. Our study analyses the relationships between seafloor features, deeper structures and fluid migration through the Plio-Quaternary sedimentary pile. The geometrical characteristics, mechanisms of formation and kinematics of four main groups of seabed features have been investigated. (i) A 150km2 field of pockmarks can be observed on the Basque margin. These features are cone-shaped circular or elliptical depressions that are either randomly distributed as small pockmarks (diameter < 20m) or aligned in trains of large pockmarks (ranging from 200 to 600m in diameter) along shallow troughs leading downstream to the Capbreton Canyon. Seismic data show that most pockmarks reach the seabed through vertically staked V-shaped features but some are buried and show evidence of lateral migration through time. (ii) A second field of widely-spaced groups of pockmarks pierce the upper slope of the Aquitanian margin. These depressions are typically a few hundred meters in diameter and seem to be preferentially located in the troughs or on the stoss sides of
Rocket engine coaxial injector liquid/gas interface flow phenomena
Mayer, W.; Kruelle, G.
1995-05-01
Coaxial injectors are used for the injection and mixing of propellants H2/O2 in cryogenic rocket engines. The aim of the theoretical and experimental investigations presented here is to elucidate some of the physical processes in coaxial injector flow with respect to their significance for atomization and mixing. Experiments with the simulation fluids H2O and air were performed under ambient conditions and at elevated counter pressures up to 20 bar. This article reports on phenomenological studies of spray generation under a broad variation of parameters using nanolight photography and high-speed cinematography (up to 3 x 10(exp 4) frames/s). Detailed theoretical and experimental studies of the surface evolution of turbulent jets were performed. Proof was obtained of the impact of internal fluid jet motions on surface deformation. The m = 1 nonaxisymmetric instability of the liquid jet seems to be superimposed onto the small-scale atomization process. A model is presented that calculates droplet atomization quantities as frequency, droplet diameter, and liquid core shape. The overall procedure for implementing this model as a global spray model is also described and an example calculation is presented. 15 refs.
NASA Astrophysics Data System (ADS)
Zhou, Xinquan; Doup, Benjamin; Sun, Xiaodong
2013-12-01
Liquid-phase turbulence measurements were performed in an air-water two-phase flow loop with a circular test section of 50 mm inner diameter using a particle image velocimetry (PIV) system. An optical phase separation method--planar laser-induced fluorescence (PLIF) technique—which uses fluorescent particles and an optical filtration technique, was employed to separate the signals of the fluorescent seeding particles from those due to bubbles and other noises. An image pre-processing scheme was applied to the raw PIV images to remove the noise residuals that are not removed by the PLIF technique. In addition, four-sensor conductivity probes were adopted to measure the radial distribution of the void fraction. Two benchmark tests were performed: the first was a comparison of the PIV measurement results with those of similar flow conditions using thermal anemometry from previous studies; the second quantitatively compared the superficial liquid velocities calculated from the local liquid velocity and void fraction measurements with the global liquid flow rate measurements. The differences of the superficial liquid velocity obtained from the two measurements were bounded within ±7% for single-phase flows and two-phase bubbly flows with the area-average void fraction up to 18%. Furthermore, a preliminary uncertainty analysis was conducted to investigate the accuracy of the two-phase PIV measurements. The systematic uncertainties due to the circular pipe curvature effects, bubble surface reflection effects and other potential uncertainty sources of the PIV measurements were discussed. The purpose of this work is to facilitate the development of a measurement technique (PIV-PLIF) combined with image pre-processing for the liquid-phase turbulence in gas-liquid two-phase flows of relatively high void fractions. The high-resolution data set can be used to more thoroughly understand two-phase flow behavior, develop liquid-phase turbulence models, and assess high
NASA Astrophysics Data System (ADS)
Wang, Z.; McKeown Walker, S.; Tamai, A.; Wang, Y.; Ristic, Z.; Bruno, F. Y.; de la Torre, A.; Riccò, S.; Plumb, N. C.; Shi, M.; Hlawenka, P.; Sánchez-Barriga, J.; Varykhalov, A.; Kim, T. K.; Hoesch, M.; King, P. D. C.; Meevasana, W.; Diebold, U.; Mesot, J.; Moritz, B.; Devereaux, T. P.; Radovic, M.; Baumberger, F.
2016-08-01
Surfaces and interfaces offer new possibilities for tailoring the many-body interactions that dominate the electrical and thermal properties of transition metal oxides. Here, we use the prototypical two-dimensional electron liquid (2DEL) at the SrTiO3(001) surface to reveal a remarkably complex evolution of electron-phonon coupling with the tunable carrier density of this system. At low density, where superconductivity is found in the analogous 2DEL at the LaAlO3/SrTiO3 interface, our angle-resolved photoemission data show replica bands separated by 100 meV from the main bands. This is a hallmark of a coherent polaronic liquid and implies long-range coupling to a single longitudinal optical phonon branch. In the overdoped regime the preferential coupling to this branch decreases and the 2DEL undergoes a crossover to a more conventional metallic state with weaker short-range electron-phonon interaction. These results place constraints on the theoretical description of superconductivity and allow a unified understanding of the transport properties in SrTiO3-based 2DELs.
Wang, Z; McKeown Walker, S; Tamai, A; Wang, Y; Ristic, Z; Bruno, F Y; de la Torre, A; Riccò, S; Plumb, N C; Shi, M; Hlawenka, P; Sánchez-Barriga, J; Varykhalov, A; Kim, T K; Hoesch, M; King, P D C; Meevasana, W; Diebold, U; Mesot, J; Moritz, B; Devereaux, T P; Radovic, M; Baumberger, F
2016-08-01
Surfaces and interfaces offer new possibilities for tailoring the many-body interactions that dominate the electrical and thermal properties of transition metal oxides. Here, we use the prototypical two-dimensional electron liquid (2DEL) at the SrTiO3(001) surface to reveal a remarkably complex evolution of electron-phonon coupling with the tunable carrier density of this system. At low density, where superconductivity is found in the analogous 2DEL at the LaAlO3/SrTiO3 interface, our angle-resolved photoemission data show replica bands separated by 100 meV from the main bands. This is a hallmark of a coherent polaronic liquid and implies long-range coupling to a single longitudinal optical phonon branch. In the overdoped regime the preferential coupling to this branch decreases and the 2DEL undergoes a crossover to a more conventional metallic state with weaker short-range electron-phonon interaction. These results place constraints on the theoretical description of superconductivity and allow a unified understanding of the transport properties in SrTiO3-based 2DELs. PMID:27064529
A Study of Liquid Metal Film Flow, Under Fusion Relevant Magnetic Fields
Narula, M.; Ying, A.; Abdou, M.A.
2005-04-15
The use of flowing liquid metal streams or 'liquid walls' as a plasma contact surface is a very attractive option and has received considerable attention over the past several years both in the plasma physics and fusion engineering programs. A key issue for the feasibility of flowing liquid metal plasma facing component (PFC) systems, lies in their magnetohydrodynamic (MHD) behavior. The spatially varying magnetic field environment, typical of a fusion device can lead to serious flow disrupting MHD forces that hinder the development of a smooth and controllable flow needed for PFC applications. The present study builds up on the ongoing research effort at UCLA, directed towards providing qualitative and quantitative data on liquid metal free surface flow behavior under fusion relevant magnetic fields, to aid in better understanding of flowing liquid metal PFC systems.
Feedback control of flow alignment in sheared liquid crystals.
Strehober, David A; Schöll, Eckehard; Klapp, Sabine H L
2013-12-01
Based on a continuum theory, we investigate the manipulation of the nonequilibrium behavior of a sheared liquid crystal via closed-loop feedback control. Our goal is to stabilize a specific dynamical state, that is, the stationary "flow alignment," under conditions where the uncontrolled system displays oscillatory director dynamics with in-plane symmetry. To this end we employ time-delayed feedback control (TDFC), where the equation of motion for the ith component q(i)(t) of the order parameter tensor is supplemented by a control term involving the difference q(i)(t)-q(i)(t-τ). In this diagonal scheme, τ is the delay time. We demonstrate that the TDFC method successfully stabilizes flow alignment for suitable values of the control strength K and τ; these values are determined by solving an exact eigenvalue equation. Moreover, our results show that only small values of K are needed when the system is sheared from an isotropic equilibrium state, contrary to the case where the equilibrium state is nematic. PMID:24483470
Feedback control of flow alignment in sheared liquid crystals
NASA Astrophysics Data System (ADS)
Strehober, David A.; Schöll, Eckehard; Klapp, Sabine H. L.
2013-12-01
Based on a continuum theory, we investigate the manipulation of the nonequilibrium behavior of a sheared liquid crystal via closed-loop feedback control. Our goal is to stabilize a specific dynamical state, that is, the stationary "flow alignment," under conditions where the uncontrolled system displays oscillatory director dynamics with in-plane symmetry. To this end we employ time-delayed feedback control (TDFC), where the equation of motion for the ith component qi(t) of the order parameter tensor is supplemented by a control term involving the difference qi(t)-qi(t-τ). In this diagonal scheme, τ is the delay time. We demonstrate that the TDFC method successfully stabilizes flow alignment for suitable values of the control strength K and τ; these values are determined by solving an exact eigenvalue equation. Moreover, our results show that only small values of K are needed when the system is sheared from an isotropic equilibrium state, contrary to the case where the equilibrium state is nematic.
Mass flow of a volatile organic liquid mixture in soils
Gerstl, Z.; Galin, Ts.; Yaron, B.
1994-05-01
The flow of kerosene, a volatile organic liquid mixture (VOLM), was studied in loam and clay soils and in a medium sand. The kerosene residual capacity and conductivity were determined for all three media at different initial moisture contents and with kerosene of different compositions. The kerosene conductivity of the soil was found to be strongly influenced by the soil texture and initial moisture content as well as by the kerosene composition. The kerosene conductivity of the sand was two orders of magnitude greater than that of the soils and was unaffected by initial moisture contents as high as field capacity. The kerosene conductivity of the loam soil was similar in oven dry and air dry soils, but increased significantly in soils at 70% and fun field capacity due to the Yuster effect. In the clay soil the kerosene conductivity of the air dry sod was four times that of the oven dry sod and increased somewhat in the soil at 70% field capacity. No kerosene flow was observed in the oven dry soil at full field capacity. The differences in kerosene conductivity in these soils and the effect of moisture content were attributed to the different pore-sin distributions of the soil& Changes in the composition of the kerosene due to volatilization of the light fractions resulted in increased viscosity of the residual kerosene. This increased viscosity affected the fluid properties of kerosene, which resulted in decreased kerosene conductivity in the sand and the soils. 29 refs., 4 figs., 4 tabs.
Simulations of a Liquid Hydrogen Inducer at Low-Flow Off-Design Flow Conditions
NASA Technical Reports Server (NTRS)
Hosangadi, A.; Ahuja, V.; Ungewitter, R. J.
2005-01-01
The ability to accurately model details of inlet back flow for inducers operating a t low-flow, off-design conditions is evaluated. A sub-scale version of a three-bladed liquid hydrogen inducer tested in water with detailed velocity and pressure measurements is used as a numerical test bed. Under low-flow, off-design conditions the length of the separation zone as well as the swirl velocity magnitude was under predicted with a standard k-E model. When the turbulent viscosity coefficient was reduced good comparison was obtained a t all the flow conditions examined with both the magnitude and shape of the profile matching well with the experimental data taken half a diameter upstream of the leading edge. The velocity profiles and incidence angles a t the leading edge itself were less sensitive to the back flow length predictions indicating that single-phase performance predictions may be well predicted even if the details of flow separation modeled are incorrect. However, for cavitating flow situations the prediction of the correct swirl in the back flow and the pressure depression in the core becomes critical since it leads to vapor formation. The simulations have been performed using the CRUNCH CFD(Registered Trademark) code that has a generalized multi-element unstructured framework and a n advanced multi-phase formulation for cryogenic fluids. The framework has been validated rigorously for predictions of temperature and pressure depression in cryogenic fluid cavities and has also been shown to predict the cavitation breakdown point for inducers a t design conditions.
2d-LCA - an alternative to x-wires
NASA Astrophysics Data System (ADS)
Puczylowski, Jaroslaw; Hölling, Michael; Peinke, Joachim
2014-11-01
The 2d-Laser Cantilever Anemometer (2d-LCA) is an innovative sensor for two-dimensional velocity measurements in fluids. It uses a micostructured cantilever made of silicon and SU-8 as a sensing element and is capable of performing mesurements with extremly high temporal resolutions up to 150 kHz. The size of the cantilever defines its spatial resolution, which is in the order of 150 μm only. Another big feature is a large angular range of 180° in total. The 2d-LCA has been developed as an alternative measurement method to x-wires with the motivation to create a sensor that can operate in areas where the use of hot-wire anemometry is difficult. These areas include measurements in liquids and in near-wall or particle-laden flows. Unlike hot-wires, the resolution power of the 2d-LCA does not decrease with increasing flow velocity, making it particularly suitable for measurements in high speed flows. Comparative measurements with the 2d-LCA and hot-wires have been carried out in order to assess the performance of the new anemometer. The data of both measurement techniques were analyzed using the same stochastic methods including a spectral analysis as well as an inspection of increment statistics and structure functions. Furthermore, key parameters, such as mean values of both velocity components, angles of attack and the characteristic length scales were determined from both data sets. The analysis reveals a great agreement between both anemometers and thus confirms the new approach.
Modeling of two-layer liquid-gas flow with account for evaporation
NASA Astrophysics Data System (ADS)
Goncharova, O. N.; Rezanova, E. V.; Lyulin, Yu. V.; Kabov, O. A.
2015-09-01
Two-layer gas-liquid flows and evaporation intensity at the interface were studied. The influence of gas flow rate, longitudinal gradient of temperature, the Soret effect on the nature of flow and transfer processes was demonstrated. Experimental and theoretical results were compared; they show dependence of evaporation at the interface on gas flow rates.
Electric current induced flow of liquid metals: Mechanism and substrate-surface effects
Kumar, P.; Howarth, J.; Dutta, I.
2014-01-28
Long range, continuous flow of liquid metals occurs upon application of an electric current. Here, we report experimental results elucidating the mechanism of current-induced liquid metal flow, and its dependence on substrate surface condition. It is shown that the observed flow is diffusion-controlled, with the flow-rate depending linearly on applied current density, indicating that it is driven by electromigration. The effective charge number for liquid electromigration, Z*, of several pure metals, such as Al, Bi, Ga, Sn, and Pb, were deduced from the experimental results and were found to be close to the elemental valency. With the exception of liquid Pb, Z* for all liquid metals tested in this study were positive, indicating that: (i) electron wind contributes much less to Z* in liquid metals than in solids, and (ii) with a few exceptions, liquid metals generally flow in the direction of the electric current. On smooth substrates which are wetted well by the liquid metal, flow occurs in a thin, continuous stream. On rough surfaces which are poorly wetted, on the other hand, discrete beads of liquid form, with mass transport between adjacent beads occurring by surface diffusion on the substrate. A rationale for the role of substrate roughness in fostering this observed transition in flow mechanism is presented.
Experiment and computational simulations of liquid-liquid flow displacement in microchannels
NASA Astrophysics Data System (ADS)
Lu, Yu; Simmons, Mark
2015-11-01
Microfluidics has great potential for tight process control in the generation of high value-added products and there is a requirement to understand how one fluid displaces another for either cleaning or control of the interfacial phenomena. Micro-Particle Image Velocimetry (μ-PIV) and shadowgraphy have been used to examine the injection of a fluid into a circular or semi-circular microchannel (with diameters of 200 μm and 205 μm respectively) which is pre-filled with another fluid. Both immiscible and miscible Newtonian fluid pairs with varying viscosity ratio have been used. Flow instabilities and regimes have been observed which can be characterised using dimensionless flow maps. Displacement efficiency, residual liquid film thickness on the wall, velocity fields and the effect of wall conditions such as wall wettability are also studied. The flow phenomena observed have been modelled using the finite volume ANSYS Fluent CFD package and compared with the experiments. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.
2005-07-01
Aniso2d is a two-dimensional seismic forward modeling code. The earth is parameterized by an X-Z plane in which the seismic properties Can have monoclinic with x-z plane symmetry. The program uses a user define time-domain wavelet to produce synthetic seismograms anrwhere within the two-dimensional media.
NASA Astrophysics Data System (ADS)
Miura, Masato; Ueki, Yoshitaka; Yokomine, Takehiko; Kunugi, Tomoaki
2012-11-01
Magnetohydrodynamics (MHD) problem which is caused by interaction between electrical conducting fluid flow and the magnetic field is one of the biggest problem in the liquid metal blanket of the fusion reactor. In the liquid metal blanket concept, it is necessary to distribute liquid metal flows uniformly in the manifold because imbalance of flow rates should affect the heat transfer performance directly, which leads to safety problem. While the manifold is insulated electrically as well as the flow duct, the 3D-MHD effect on the flowing liquid metal in the manifold is more apparent than that in straight duct. With reference to the flow distribution in this concept, the liquid metal flow in the electrical insulating manifold under the uniform transverse magnetic field is investigated experimentally. In this study, GaInSn is selected as working fluid. The experimental system includes the electrical magnet and the manifold test section which is made of acrylic resin for perfectly electrical insulation. The liquid metal flows in a non-symmetric 180°-turn with manifold, which consists of one upward channel and two downward channels. The flow rates in each channel are measured by electromagnetic flow meters for several combinations Reynolds number and Hartman number. The effects of magnetic field on the uniformity of flow distribution are cleared.
NASA Astrophysics Data System (ADS)
Kundu, Santanu
The microstructure development within mesophase pitch-based carbon materials depends on the flow history that the pitch is subjected to. Therefore, a fundamental understanding of flow and its influence on the microstructure is required to obtain carbon materials with desired properties. The objective of this research was to investigate the flow and microstructural behavior of a synthetic mesophase pitch (AR-HP) in rheometric and processing flow conditions. In addition, simulation studies were performed to establish a frame work for modeling the flow behavior of this complex material in different flow situations. The steady-shear viscosities obtained from a cone-plate rheometer during increasing rate-sweep experiments exhibited shear-thinning (Region I) and plateau (Region II) responses. However, the slope of the shear-thinning region was only about -0.2, much lower than -0.5 observed in some pitches and liquid-crystalline polymers. This difference could arise from the different molecular constituents of pitches. At higher shear rates, as measured from capillary rheometers, the viscosity values remained almost constant. The transient shear stress responses, as measured from cone-plate rheometer, exhibited nonmonotonic behavior as a function of applied strain at all shear rates and temperatures tested. After rheological experiments, the samples were collected by developing a new experimental protocol for preservation of the sample for microstructural analysis. Microstructural observations obtained from three orthogonal sections, reported for the first time in the literature, indicate that the local maximum in shear stress was due to yielding of initial microstructure. The microstructure became flow oriented with further shearing, and the structure size decreased with increasing shear rates. In addition to high-strain experiments, dynamic experiments were also performed in the linear viscoelastic region where no significant deformation of fluid takes place. The
Effect of surface condition on the flow in segmented gas-liquid microreactors
NASA Astrophysics Data System (ADS)
Pouya, Shahram; Koochesfahani, Manoochehr
2010-11-01
The mixing process within segmented gas-liquid microreactors is of significance importance in design and optimization of devices for high throughput material synthesis. In a typical slug flow regime the liquid slugs are connected through a thin liquid film that plays an important role in hydrodynamics of the microreactor flow. Among the parameters that can influence the thin film layer, and the overall flow, is the surface condition of microchannel walls. We present preliminary results of this influence in the segmented gas-liquid flow of Ethanol/Nitrogen within PDMS microreactors. The results are presented specifically for microreactors with different level of roughness on the channel walls. The range of stable slug flow regime and behavior of liquid film are studied as a function of surface roughness.
NASA Astrophysics Data System (ADS)
Wu, C.; Chang, T.
2010-12-01
A new method in describing the multifractal characteristics of intermittent events was introduced by Cheng and Wu [Chang T. and Wu C.C., Physical Rev, E77, 045401(R), 2008]. The procedure provides a natural connection between the rank-ordered spectrum and the idea of one-parameter scaling for monofractals. This technique has been demonstrated using results obtained from a 2D MHD simulation. It has also been successfully applied to in-situ solar wind observations [Chang T., Wu, C.C. and Podesta, J., AIP Conf Proc. 1039, 75, 2008], and the broadband electric field oscillations from the auroral zone [Tam, S.W.Y. et al., Physical Rev, E81, 036414, 2010]. We take the next step in this procedure. By using the ROMA spectra and the scaled probability distribution functions (PDFs), raw PDFs can be calculated, which can be compared directly with PDFs from observations or simulation results. In addition to 2D MHD simulation results and in-situ solar wind observation, we show clearly using the ROMA analysis the multifractal character of the 3D fluid simulation data obtained from the JHU turbulence database cluster at http://turbulence.pha.jhu.edu. In particular, we show the scaling of the non-symmetrical PDF for the parallel-velocity fluctuations of this 3D fluid data.
Special Features in Application of Nuclear Magnetic Spectroscopy to Study Flows of Liquid Media
NASA Astrophysics Data System (ADS)
Davydov, V. V.; Dudkin, V. I.; Karseev, A. Yu.; Vologdin, V. A.
2016-01-01
We consider the special features involved in studying flows of liquid media using a nuclear magnetic resonance spectrometer. Taking these special features into account in the design of the NMR spectrometer lets us determine the relative concentrations of paramagnetic ions, and also lets us measure the longitudinal (T1 ) and transverse (T2 ) relaxation times within <0.5% in liquid flows. This lets us completely eliminate errors in determining the state of the flowing medium using the measured relaxation constants T1 and T2, which is especially important when working with medicinal suspensions and biological solutions. We present the results of experimental studies on flows of liquid media.
NASA Astrophysics Data System (ADS)
Li, L.; Xu, S. L.; Ren, Y. J.; Liu, G. R.; Ren, X. B.; Xie, W. J.; Li, Y. C.; Wang, Z. L.
The liquid flow during the process of liquid explosion dissemination is a typical complex high-speed unsteady motion with multi-scale in space and time. The motion of liquid flow may be partitioned to several stages. The first is initial liquid expansion by the action of shock wave and explosive gaseous products. The second is breakup of liquid annulus and turbulent mixing, which is called near-field flow. The third is two-phase mixing flow of gas and liquid drops, which is called far-field flow. To first stage, a compressible inviscid liquid model was used, while an elastic and plastic model was used to depict the expansion of solid shell. Numerical study in two dimensional has been made by using the Arbitrary Euler-Lagrange (ALE) methods. In near-field, the unstable flow of liquid annulus is dominated by many factors. (1) The shock action of gaseous expansive products. (2) The geometric structure of wave system in liquid. (3) The local bubble and cavitating flow in annulus, induce much of local unstable interface, tear up interfaces, and enhance the instability and breakup of liquid annulus. In this paper, some postulations are proposed that the cavitations in liquid annulus are induced by shock wave and the flow of liquid annulus is a two phase flow (liquid and a discrete bubble groups). Some experimental results will be presented that the breakup of interface and turbulent mixing is visualized qualitatively and measured quantitatively by using shadow photography method. The primary results are some flow patten of interfaces and some transient flow parameters by which the nonlinear character will be obtained, and provide an experiential support for modeling to unstable interface flow and turbulent mixing. The two-phase mixing flow between liquid drops and gas in far-field can be studied by numerical methods where the turbulent motion of gas phase is represented with k-ɛ model in Euler system, the motion of particle phase is represented with particle stochastic
Equation of DNB Heat Flux for Upward Forced Flow of Cryogenic Liquids
NASA Astrophysics Data System (ADS)
Shiotsu, M.; Tatsumoto, H.; Shirai, Y.; Hata, K.; Naruo, Y.; Kobayashi, H.; Inatani, Y.; Kinoshita, K.
Knowledge of departure from nucleate boiling (DNB) heat flux is important for design of superconducting systems cooled by cryogenic liquids. We have already presented the equation of DNB heat flux that can describe the experimental data of liquid hydrogen. To see the applicability of the equation to other cryogenic liquids, similar heat transfer tests in forced flow of liquid nitrogen are performed for wide ranges of conditions in this work. It was confirmed that the DNB heat flux equation derived by the authors can express not only the data for liquid hydrogen but also those for liquid nitrogen.
Control of Flowing Liquid Films by Electrostatic Fields in Space
NASA Technical Reports Server (NTRS)
Griffing, E. M.; Bankoff, S. G.; Schluter, R. A.; Miksis, M. J.
1999-01-01
The interaction of a spacially varying electric field and a flowing thin liquid film is investigated experimentally for the design of a proposed light weight space radiator. Electrodes are utilized to create a negative pressure at the bottom of a fluid film and suppress leaks if a micrometeorite punctures the radiator surface. Experimental pressure profiles under a vertical falling film, which passes under a finite electrode, show that fields of sufficient strength can be used safely in such a device. Leak stopping experiments demonstrate that leaks can be stopped with an electric field in earth gravity. A new type of electrohydrodynamic instability causes waves in the fluid film to develop into 3D cones and touch the electrode at a critical voltage. Methods previously used to calculate critical voltages for non moving films are shown to be inappropriate for this situation. The instability determines a maximum field which may be utilized in design, so the possible dependence of critical voltage on electrode length, height above the film, and fluid Reynolds number is discussed.
Greg Flach, Frank Smith
2011-12-31
Mesh2d is a Fortran90 program designed to generate two-dimensional structured grids of the form [x(i),y(i,j)] where [x,y] are grid coordinates identified by indices (i,j). The x(i) coordinates alone can be used to specify a one-dimensional grid. Because the x-coordinates vary only with the i index, a two-dimensional grid is composed in part of straight vertical lines. However, the nominally horizontal y(i,j0) coordinates along index i are permitted to undulate or otherwise vary. Mesh2d also assigns an integer material type to each grid cell, mtyp(i,j), in a user-specified manner. The complete grid is specified through three separate input files defining the x(i), y(i,j), and mtyp(i,j) variations.
2011-12-31
Mesh2d is a Fortran90 program designed to generate two-dimensional structured grids of the form [x(i),y(i,j)] where [x,y] are grid coordinates identified by indices (i,j). The x(i) coordinates alone can be used to specify a one-dimensional grid. Because the x-coordinates vary only with the i index, a two-dimensional grid is composed in part of straight vertical lines. However, the nominally horizontal y(i,j0) coordinates along index i are permitted to undulate or otherwise vary. Mesh2d also assignsmore » an integer material type to each grid cell, mtyp(i,j), in a user-specified manner. The complete grid is specified through three separate input files defining the x(i), y(i,j), and mtyp(i,j) variations.« less
NASA Astrophysics Data System (ADS)
Lotsch, Bettina V.
2015-07-01
Graphene's legacy has become an integral part of today's condensed matter science and has equipped a whole generation of scientists with an armory of concepts and techniques that open up new perspectives for the postgraphene area. In particular, the judicious combination of 2D building blocks into vertical heterostructures has recently been identified as a promising route to rationally engineer complex multilayer systems and artificial solids with intriguing properties. The present review highlights recent developments in the rapidly emerging field of 2D nanoarchitectonics from a materials chemistry perspective, with a focus on the types of heterostructures available, their assembly strategies, and their emerging properties. This overview is intended to bridge the gap between two major—yet largely disjunct—developments in 2D heterostructures, which are firmly rooted in solid-state chemistry or physics. Although the underlying types of heterostructures differ with respect to their dimensions, layer alignment, and interfacial quality, there is common ground, and future synergies between the various assembly strategies are to be expected.
Experimental investigation of non-Newtonian/Newtonian liquid-liquid flow in microchannel
NASA Astrophysics Data System (ADS)
Roumpea, Eynagelia-Panagiota; Weheliye, Weheliye; Chinaud, Maxime; Angeli, Panagiota; Lyes Kahouadji Collaboration; Omar. K. Matar Collaboration
2015-11-01
Plug flow of an organic phase and an aqueous non-Newtonian solution was investigated experimentally in a quartz microchannel with I.D. 200 μm. The aqueous phase was a glycerol solution where 1000 and 2000 ppm of xanthan gum was added while the organic phase was silicon oil with 155 and 5 cSt viscosity. The two phases were brought together in a T-junction and their flowrates varied from 0.3 to 6 ml/hr. High speed imaging was used to study the characteristics of the plugs and the effect of the liquid properties on the flow patterns while a two-colour micro-PIV technique was used to investigate velocity profiles and circulation patterns within the plugs. The experimental results revealed that plug length was affected by both flowrate and viscosity. In all cases investigated, a film of the continuous phase always surrounded the plugs and its thickness was compared with existing literature models. Circulation patterns inside plugs were obtained by subtracting the plug velocity and found to be depended on the plug length and the amount of xanthan gum in the aqueous phase. Finally, the dimensionless circulation time was calculated and plotted as a function of the plug length. Department of Chemical Engineering South Kensington Campus Imperial College London SW7 2AZ.
Li, Cunman; Zhao, Yanyan; Guo, Zhimou; Zhang, Xiuli; Xue, Xingya; Liang, Xinmiao
2014-10-01
An effective method aiming at enrichment and analysis of micro-components in traditional Chinese medicine (TCM) was developed. One fraction (fraction E) from the extract of Hedyotis diffusa Willd. was selected as test sample, which was isolated by using the XAD-4 macroporous resin. To study the micro-components, a two-dimensional reverse-phase liquid chromatography (2D-RPLC/RPLC) method was developed, comprising Click OEG and C18 stationary phases as the first and second dimensions, respectively. Of the eight sub-fractions isolated from the first dimension, three sub-fractions (fractions II-IV) containing micro-components were further separated with the second dimension. The 2D-RPLC/RPLC system was proved to possess high orthogonality. Furthermore, the micro-components were characterized by using ultra-performance liquid chromatography-diode array detector/quadrupole time-of-flight mass spectrometry (UPLC-DAD/Q-TOF MS) with electrospray ionization (ESI) source. With the optimized separation and characterization method, a large number (>400) of micro-components were enriched and detected from the extracts of H. diffusa Willd., the majority of which has not been isolated from the herb before. Among these isolated micro-components, 38 compounds involving 24 phenylpropanoids, 7 flavonoids and 7 iridoid glucosides (IGs), were identified or tentatively identified from the H. diffusa extracts on the basis of spectral data of the authentic standards and the fragmentation characteristics information available in literatures. The proposed method made it possible to effectively screen and analyze the micro-components in TCMs or other complex natural medicines. PMID:25061712
Jubin, R.T.; Randolph, J.D.
1991-06-18
This patent describes a centrifugal contactor for solvent extraction systems. The centrifugal contactor is provided with an annular vertically oriented mixing chamber between the rotor housing and the rotor for mixing process liquids such as the aqueous and organic phases of the solvent extraction process used for nuclear fuel reprocessing. A set of stationary helically disposed vanes carried by the housing is in the lower region of the mixing chamber at a location below the process-liquid inlets for the purpose of urging the liquids in an upward direction toward the inlets and enhancing the mixing of the liquids and mass transfer between the liquids. The upper region of the mixing vessel above the inlets for the process liquids is also provided with a set helically disposed vanes carried by the housing for urging the process liquids in a downward direction when the liquid flow rates through the inlets are relatively high and the liquids contact the vane set in the upper region. The use of these opposing vane sets in the mixing zone maintains the liquid in the mixing zone at suitable levels.
Rheological Properties of Quasi-2D Fluids in Microgravity
NASA Technical Reports Server (NTRS)
Stannarius, Ralf; Trittel, Torsten; Eremin, Alexey; Harth, Kirsten; Clark, Noel; Maclennan, Joseph; Glaser, Matthew; Park, Cheol; Hall, Nancy; Tin, Padetha
2015-01-01
In recent years, research on complex fluids and fluids in restricted geometries has attracted much attention in the scientific community. This can be attributed not only to the development of novel materials based on complex fluids but also to a variety of important physical phenomena which have barely been explored. One example is the behavior of membranes and thin fluid films, which can be described by two-dimensional (2D) rheology behavior that is quite different from 3D fluids. In this study, we have investigated the rheological properties of freely suspended films of a thermotropic liquid crystal in microgravity experiments. This model system mimics isotropic and anisotropic quasi 2D fluids [46]. We use inkjet printing technology to dispense small droplets (inclusions) onto the film surface. The motion of these inclusions provides information on the rheological properties of the films and allows the study of a variety of flow instabilities. Flat films have been investigated on a sub-orbital rocket flight and curved films (bubbles) have been studied in the ISS project OASIS. Microgravity is essential when the films are curved in order to avoid sedimentation. The experiments yield the mobility of the droplets in the films as well as the mutual mobility of pairs of particles. Experimental results will be presented for 2D-isotropic (smectic-A) and 2D-nematic (smectic-C) phases.
Observations of Gas-Liquid Flows Through Contractions in Microgravity
NASA Technical Reports Server (NTRS)
McQuillen, John
1996-01-01
Tests were conducted for an air-water flow through two sudden contractions aboard the NASA DC-9 low gravity aircraft. Flow rate, residual accelerations, void fraction, film thickness, and pressure drop data were recorded and flow visualization at 250 images per second were recorded. Some preliminary results based on the flow visualization data are presented for bubbly, slug and annular flow.
Large-Flow-Area Flow-Selective Liquid/Gas Separator
NASA Technical Reports Server (NTRS)
Vasquez, Arturo; Bradley, Karla F.
2010-01-01
This liquid/gas separator provides the basis for a first stage of a fuel cell product water/oxygen gas phase separator. It can separate liquid and gas in bulk in multiple gravity environments. The system separates fuel cell product water entrained with circulating oxygen gas from the outlet of a fuel cell stack before allowing the gas to return to the fuel cell stack inlet. Additional makeup oxygen gas is added either before or after the separator to account for the gas consumed in the fuel cell power plant. A large volume is provided upstream of porous material in the separator to allow for the collection of water that does not exit the separator with the outgoing oxygen gas. The water then can be removed as it continues to collect, so that the accumulation of water does not impede the separating action of the device. The system is designed with a series of tubes of the porous material configured into a shell-and-tube heat exchanger configuration. The two-phase fluid stream to be separated enters the shell-side portion of the device. Gas flows to the center passages of the tubes through the porous material and is then routed to a common volume at the end of the tubes by simple pressure difference from a pumping device. Gas flows through the porous material of the tubes with greater ease as a function of the ratio of the dynamic viscosity of the water and gas. By careful selection of the dimensions of the tubes (wall thickness, porosity, diameter, length of the tubes, number of the tubes, and tube-to-tube spacing in the shell volume) a suitable design can be made to match the magnitude of water and gas flow, developed pressures from the oxygen reactant pumping device, and required residual water inventory for the shellside volume.
MHD Effect of Liquid Metal Film Flows as Plasma-Facing Components
NASA Astrophysics Data System (ADS)
Zhang, Xiujie; Xu, Zengyu; Pan, Chuanjie
2008-12-01
Stability of liquid metal film flow under gradient magnetic field is investigated. Three dimensional numerical simulations on magnetohydrodynamics (MHD) effect of free surface film flow were carried out, with emphasis on the film thickness variation and its surface stability. Three different MHD phenomena of film flow were observed in the experiment, namely, retardant, rivulet and flat film flow. From our experiment and numerical simulation it can be concluded that flat film flow is a good choice for plasma-facing components (PFCs)
A visual study of radial inward choked flow of liquid nitrogen
NASA Technical Reports Server (NTRS)
Hendricks, R. C.; Simoneau, R. J.; Hsu, Y. Y.
1973-01-01
A visual study of the radial inward choked flow of liquid nitrogen was conducted. Data and high speed moving pictures were obtained. The study indicated the following: (1) steady radial inward choked flow seems equivalent to steady choked flow through axisymmetric nozzles, (2) transient choked flows through the radial gap are not uniform and the discharge pattern appears as nonuniform impinging jets, and (3) the critical mass flow rate data for the transient case appear different from those of the steady case.
NASA Astrophysics Data System (ADS)
Voytkov, Ivan V.; Zabelin, Maksim V.; Vysokomornaya, Olga V.
2016-02-01
The processes of heat and mass transfer were investigated experimentally while moving and evaporating the atomized water flow in high-temperature combustion products of typical liquid fuels and organic flammable liquids: gasoline, kerosene, acetone, crude oil, industrial alcohol. We determined typical periods of liquid extinguishing by an atomized water flow of various dispersability. Data of the discharge of extinguishing medium corresponding to various parameters of atomization and duration of using the atomization devices was presented. It is shown that Um≈3.5 m/s is a minimal outflow velocity of droplets during moving while passing the distance of 1m in the high-temperature gas medium to stop the combustion of organic liquids.
Effects of Gravity on Cocurrent Two-Phase Gas-Liquid Flows Through Packed Columns
NASA Technical Reports Server (NTRS)
Motil, Brian J.; Balakotaiah, Vemuri; Kamotani, Yasuhiro
2001-01-01
This work presents the experimental results of research on the influence of gravity on flow pattern transitions, pressure drop and flow characteristics for cocurrent gas-liquid two-phase flow through packed columns. The flow pattern transition data indicates that the pulse flow regime exists over a wider range of gas and liquid flow rates under reduced gravity conditions compared to normal gravity cocurrent down-flow. This is illustrated by comparing the flow regime transitions found in reduced gravity with the transitions predicted by Talmor. Next, the effect of gravity on the total pressure drop in a packed column is shown to depend on the flow regime. The difference is roughly equivalent to the liquid static head for bubbly flow but begins to decrease at the onset of pulse flow. As the spray flow regime is approached by increasing the gas to liquid ratio, the effect of gravity on pressure drop becomes negligible. Finally, gravity tends to suppress the amplitude of each pressure pulse. An example of this phenomenon is presented.
NASA Astrophysics Data System (ADS)
Matsunaga, Akio; Kasagi, Nobuhide
1993-09-01
A turbulent separated and reattaching flow was predicted with several, including two low-Reynolds number, kappa-epsilon models. These results were compared with the experimental result that was obtained through the use of three-dimensional particle tracking velocimetry. Although the standard model generally gives better results than the low-Reynolds model in the separated free shear layer, the latter works better in the near-wall region. Further improvement in the low-Reynolds kappa-epsilon model, particularly in the model parameters, should make its prediction of turbulent flows with separation and reattachment accurate enough for engineering applications.
NASA Astrophysics Data System (ADS)
Heiland, Hans Georg; Wozniak, Günter; Wozniak, Klaus
2007-07-01
Thermal convection in a small vertical gap is studied experimentally applying digital particle image velocimetry/thermometry. This optical method enables the simultaneous measurement of two-dimensional flow and temperature fields in a liquid. The principle is based on seeding the liquid flow medium with thermochromic liquid crystal particles. The temperature is measured by the crystal particles which change their reflected colour as function of temperature. The flow velocity is measured by using the same particles as flow tracers. The investigation shall contribute to the understanding of the fluid mechanical behaviour of biological liquids within micro reactor systems. However, the problem is also of fundamental interest as far as heat and mass transfer is concerned. Measured temperature and flow velocity fields are presented and discussed.
Velocity Vector Field Visualization of Flow in Liquid Acquisition Device Channel
NASA Technical Reports Server (NTRS)
McQuillen, John B.; Chao, David F.; Hall, Nancy R.; Zhang, Nengli
2012-01-01
A capillary flow liquid acquisition device (LAD) for cryogenic propellants has been developed and tested in NASA Glenn Research Center to meet the requirements of transferring cryogenic liquid propellants from storage tanks to an engine in reduced gravity environments. The prototypical mesh screen channel LAD was fabricated with a mesh screen, covering a rectangular flow channel with a cylindrical outlet tube, and was tested with liquid oxygen (LOX). In order to better understand the performance in various gravity environments and orientations at different liquid submersion depths of the screen channel LAD, a series of computational fluid dynamics (CFD) simulations of LOX flow through the LAD screen channel was undertaken. The resulting velocity vector field visualization for the flow in the channel has been used to reveal the gravity effects on the flow in the screen channel.
Cross-flow heat exchangers for anti-freezing of liquid nitrogen
NASA Astrophysics Data System (ADS)
Chang, Ho-Myung; Gwak, Kyung Hyun; Yang, Hyung Suk; Hwang, Si-Dole
2013-10-01
Cross-flow heat exchangers are proposed and experimentally investigated as an anti-freezing scheme of liquid nitrogen. The possibility of freeze-out of liquid nitrogen is an important design issue in developing long superconducting cables, as the supply temperature of liquid nitrogen is close to its freezing temperature (63.3 K). Plate-fin heat exchangers are fabricated as typical counter-flow and newly proposed two-pass cross-flow in laboratory scale, and tested with cold helium gas at temperatures below 60 K. The experimental results show that the cross-flow heat exchanger is less vulnerable to the freeze-out condition, since the temperature distribution is basically two-dimensional. The cross-flow heat exchangers are effective in avoiding a complete clog-up of all passages and reducing the risk of freeze-out of liquid nitrogen.
NASA Astrophysics Data System (ADS)
Juez, C.; Caviedes-Voullième, D.; Murillo, J.; García-Navarro, P.
2014-12-01
Dense granular flows are present in geophysics and in several industrial processes, which has lead to an increasing interest for the knowledge and understanding of the physics which govern their propagation. For this reason, a wide range of laboratory experiments on gravity-driven flows have been carried out during the last two decades. The present work is focused on geomorphological processes and, following previous work, a series of laboratory studies which constitute a further step in mimicking natural phenomena are described and simulated. Three situations are considered with some common properties: a two-dimensional configuration, variable slope of the topography and the presence of obstacles. The setup and measurement technique employed during the development of these experiments are deeply explained in the companion work. The first experiment is based on a single obstacle, the second one is performed against multiple obstacles and the third one studies the influence of a dike on which overtopping occurs. Due to the impact of the flow against the obstacles, fast moving shocks appear, and a variety of secondary waves emerge. In order to delve into the physics of these types of phenomena, a shock-capturing numerical scheme is used to simulate the cases. The suitability of the mathematical models employed in this work has been previously validated. Comparisons between computed and experimental data are presented for the three cases. The computed results show that the numerical tool is able to predict faithfully the overall behavior of this type of complex dense granular flow.
Measuring the rate of local evaporation from the liquid surface under the action of gas flow
NASA Astrophysics Data System (ADS)
Lyulin, Yu. V.; Feoktistov, D. V.; Afanas'ev, I. A.; Chachilo, E. S.; Kabov, O. A.; Kuznetsov, G. V.
2015-07-01
The dynamics of evaporation from the surface of a liquid layer under the action of a gas flow has been studied. Correlation dependences of the rate of liquid evaporation on the gas flow rate and temperature for the ethanol-air system have been obtained and compared to other published experimental data. It is established that, for the two-phase systems studied, the evaporation rate growth with increasing temperature exhibits an almost identical character independently of the thermal properties of particular liquids and gases. In contrast, the character of the evaporation rate growth with increasing gas flow velocity significantly depends on these properties.
Stopper, U.; Aigner, M.; Ax, H.; Meier, W.; Sadanandan, R.; Stoehr, M.; Bonaldo, A.
2010-04-15
Several laser diagnostic measurement techniques have been applied to study the lean premixed natural gas/air flames of an industrial swirl burner. This was made possible by equipping the burner with an optical combustion chamber that was installed in the high-pressure test rig facility at the DLR Institute of Combustion Technology in Stuttgart. The burner was operated with preheated air at various operating conditions with pressures up to p = 6 bar and a maximum thermal power of P = 1 MW. The instantaneous planar flow field inside the combustor was studied with particle image velocimetry (PIV). Planar laser induced fluorescence (PLIF) of OH radicals on a single-shot basis was used to determine the shape and the location of the flame front as well as the spatial distribution of reaction products. 1D laser Raman spectroscopy was successfully applied for the measurement of the temperature and the concentration of major species under realistic gas turbine conditions. Results of the flow field analysis show the shape and the size of the main flow regimes: the inflow region, the inner and the outer recirculation zone. The highly turbulent flow field of the inner shear layer is found to be dominated by small and medium sized vortices. High RMS fluctuations of the flow velocity in the exhaust gas indicate the existence of a rotating exhaust gas swirl. From the PLIF images it is seen that the primary reactions happened in the shear layers between inflow and the recirculation zones and that the appearance of the reaction zones changed with flame parameters. The results of the multiscalar Raman measurements show a strong variation of the local mixture fraction allowing conclusions to be drawn about the premix quality. Furthermore, mixing effects of unburnt fuel and air with fully reacted combustion products are studied giving insights into the processes of the turbulence-chemistry interaction. (author)
Bae, Soo Hyeon; Lee, Joeng Kee; Cho, Doo-Yeoun; Bae, Soo Kyung
2014-06-01
A rapid and simple LC with MS/MS method for the simultaneous determination of metoprolol and its two CYP2D6-derived metabolites, α-hydroxy- and O-desmethylmetoprolol, in human plasma was established. Metoprolol (MET), its two metabolites, and the internal standard chlorpropamide were extracted from plasma (50 μL) using ethyl acetate. Chromatographic separation was performed on a Luna CN column with an isocratic mobile phase consisting of distilled water and methanol containing 0.1% formic acid (60:40, v/v) at a flow rate of 0.3 mL/min. The total run time was 3.0 min per sample. Mass spectrometric detection was conducted by ESI in positive ion selected-reaction monitoring mode. The linear ranges of concentration for MET, α-hydroxymetoprolol, and O-desmethylmetoprolol were 2-1000, 2-500, and 2-500 ng/mL, respectively, with a lower limit of quantification of 2 ng/mL for all analytes. The coefficient of variation for the assay's precision was ≤ 13.2%, and the accuracy was 89.1-110%. All analytes were stable under various storage and handling conditions and no relevant cross-talk and matrix effect were observed. Finally, this method was successfully applied to assess the influence of CYP2D6 genotypes on the pharmacokinetics of MET after oral administration of 100 mg to healthy Korean volunteers. PMID:24648255
Effect of ambient pressure on liquid swirl injector flow dynamics
NASA Astrophysics Data System (ADS)
Chen, Xiaodong; Yang, Vigor
2014-10-01
In this paper, a combined theoretical and numerical analysis is performed to study the internal and external flowfields of a liquid swirl injector. The effect of ambient pressure on the injector dynamics is explored systematically over a range of 1-50 atm. An increase in the ambient pressure increases the liquid film thickness, but decreases the spreading angle. This phenomenon can be attributed to the modification of the velocity profiles within the liquid film near the gas-liquid interface due to the alteration of the gas-phase shear stresses with pressure. The friction force at the interface plays a minor role. The generation and existence of stationary waves in the injector nozzle is also considered. At a higher ambient pressure, the pressure drop across the liquid sheet downstream of the injector exit increases, thereby suppressing the spreading of the liquid sheet. This in turn increases the thickness of the liquid sheet, and subsequently increases the breakup length at higher pressure. A semi-empirical model is developed to relate the velocity and pressure distributions near the surface of the liquid sheet. Good agreement is achieved between the measured and predicted shape and spreading angle of the liquid sheet.
A Study of Bubble and Slug Gas-Liquid Flow in a Microgravity Environment
NASA Technical Reports Server (NTRS)
McQuillen, J.
2000-01-01
The influence of gravity on the two-phase flow dynamics is obvious.As the gravity level is reduced,there is a new balance between inertial and interfacial forces, altering the behavior of the flow. In bubbly flow,the absence of drift velocity leads to spherical-shaped bubbles with a rectilinear trajectory.Slug flow is a succession of long bubbles and liquid slug carrying a few bubbles. There is no flow reversal in the thin liquid film as the long bubble and liquid slug pass over the film. Although the flow structure seems to be simpler than in normal gravity conditions,the models developed for the prediction of flow behavior in normal gravity and extended to reduced gravity flow are unable to predict the flow behavior correctly.An additional benefit of conducting studies in microgravity flows is that these studies aide the development of understanding for normal gravity flow behavior by removing the effects of buoyancy on the shape of the interface and density driven shear flows between the gas and the liquid phases. The proposal calls to study specifically the following: 1) The dynamics of isolated bubbles in microgravity liquid flows will be analyzed: Both the dynamics of spherical isolated bubbles and their dispersion by turbulence, their interaction with the pipe wall,the behavior of the bubbles in accelerated or decelerated flows,and the dynamics of isolated cylindrical bubbles, their deformation in accelerated/decelerated flows (in converging or diverging channels), and bubble/bubble interaction. Experiments will consist of the use of Particle Image Velocimetry (PIV) and Laser Doppler Velocimeters (LDV) to study single spherical bubble and single and two cylindrical bubble behavior with respect to their influence on the turbulence of the surrounding liquid and on the wall 2) The dynamics of bubbly and slug flow in microgravity will be analyzed especially for the role of the coalescence in the transition from bubbly to slug flow (effect of fluid properties and
NASA Astrophysics Data System (ADS)
Mohammad, Abdulrahman Th.; Mat, Sohif Bin; Sulaiman, M. Y.; Sopian, K.; Al-abidi, Abduljalil A.
2013-11-01
A computer simulation using MATLAB is investigated to predict the distribution of air stream parameters (humidity ratio and temperature) as well as desiccant parameters (temperature and concentration) inside the parallel plate absorber. The present absorber consists of fourteen parallel plates with a surface area per unit volume ratio of 80 m2/m3. Calcium chloride as a liquid desiccant flows through the top of the plates to the bottom while the air flows through the gap between the plates making it a cross flow configuration. The model results show the effect of desiccant mass flow rate on the performance of the dehumidifier (moisture removal and dehumidifier effectiveness). Performance comparisons between present cross-flow dehumidifier and another experimental cross-flow dehumidifier in the literature are carried out. The simulation is expected to help in optimizing of a cross flow dehumidifier.
NASA Technical Reports Server (NTRS)
Monta, William J.
1992-01-01
A pitot-rake survey of the simulated exhaust of a half-span scramjet nozzle model was conducted in the Langley 20-Inch Mach 6 Tunnel to provide an additional data set for computational fluid dynamics (CFD) code comparisons. A wind-tunnel model was tested with a 26-tube pitot rake that could be manually positioned along the mid-semispan plane of the model. The model configuration had an external expansion surface of 20 degrees and an internal cowl expansion of 12 degrees; tests were also performed with a flow fence. Tests were conducted at a free-stream Reynolds number of approximately 6.5 x 10(exp 6) per foot and a model angle of attack of -0.75 degrees. The two exhaust gas mediums that were tested were air and a Freon 12-argon mixture. Each medium was tested at two jet total pressures at approximately 28 and 14 psia. This document presents the flow-field survey results in graphical as well as tabular form, and several observations concerning the results are discussed. The surveys reveal the major expected flow-field characteristics for each test configuration. For a 50-percent freon 12 and 50-percent argon mixture by volume (Fr-Ar), the exhaust jet pressures were slightly higher than those for air. The addition of a flow fence slightly raised the pitot pressure for the Fr-Ar mixture, but it produced little change for air. For the Fr-Ar exhaust, the plume was larger and the region between the shock wave and plume was smaller.
NASA Astrophysics Data System (ADS)
Adjali, Saadia; Belkadi, Mustapha; Aounallah, Mohammed; Imine, Omar
2015-05-01
Accurate simulation of turbulent free surface flows around surface ships has a central role in the optimal design of such naval vessels. The flow problem to be simulated is rich in complexity and poses many modeling challenges because of the existence of breaking waves around the ship hull, and because of the interaction of the two-phase flow with the turbulent boundary layer. In this paper, our goal is to estimate the lift and drag coefficients for NACA 0012 of hydrofoil advancing in calm water under steady conditions with free surface and emerged NACA 0015. The commercial CFD software FLUENT version 14 is used for the computations in the present study. The calculated grid is established using the code computer GAMBIT 2.3.26.The shear stress k-ωSST model is used for turbulence modeling and the volume of fluid technique is employed to simulate the free-surface motion. In this computation, the second order upwind scheme is used for discretizing the convection terms in the momentum transport equations, the Modified HRIC scheme for VOF discretisation. The results obtained compare well with the experimental data.
High average power laser using a transverse flowing liquid host
Ault, Earl R.; Comaskey, Brian J.; Kuklo, Thomas C.
2003-07-29
A laser includes an optical cavity. A diode laser pumping device is located within the optical cavity. An aprotic lasing liquid containing neodymium rare earth ions fills the optical cavity. A circulation system that provides a closed loop for circulating the aprotic lasing liquid into and out of the optical cavity includes a pump and a heat exchanger.
High throughput analysis of samples in flowing liquid
Ambrose, W. Patrick; Grace, W. Kevin; Goodwin, Peter M.; Jett, James H.; Orden, Alan Van; Keller, Richard A.
2001-01-01
Apparatus and method enable imaging multiple fluorescent sample particles in a single flow channel. A flow channel defines a flow direction for samples in a flow stream and has a viewing plane perpendicular to the flow direction. A laser beam is formed as a ribbon having a width effective to cover the viewing plane. Imaging optics are arranged to view the viewing plane to form an image of the fluorescent sample particles in the flow stream, and a camera records the image formed by the imaging optics.
Pumping of Dielectric Liquids Using Non-Uniform-Field Induced Electrohydrodynamic Flow
NASA Astrophysics Data System (ADS)
Ryu, Jae Chun; Kim, Wonkyoung; Kang, Kwan Hyoung
2010-11-01
Pumping of dielectric liquids or poorly conducting liquids is necessary in cooling of microelectronic devices, dispensing liquids in miniature systems for chemical and biological analysis, and micropumping of organic solvents for microreactor. Electrical pumping of liquids is more attractive than conventional mechanical pumping methods because of many advantages such as simple design, no mechanical parts, low acoustic noise, and lightweight. We present a new electrohydrodynamic (EHD) pumping method for dielectric liquids. The pumping method relies on the EHD flow generated by electric-field dependent electrical conductivity (Onsager effect). A polar additive plays an important role in enhancing the field-dependency of conductivity. When ac voltage is applied, a fast and regular flow was produced around electrodes. Flow speed is proportional to cube of electric-field strength and inversely to applied frequency. The experimental results showed good agreement with numerical analysis which is based on our model.
Flowmeter for determining average rate of flow of liquid in a conduit
Kennerly, John M.; Lindner, Gordon M.; Rowe, John C.
1982-01-01
This invention is a compact, precise, and relatively simple device for use in determining the average rate of flow of a liquid through a conduit. The liquid may be turbulent and contain bubbles of gas. In a preferred embodiment, the flowmeter includes an electrical circuit and a flow vessel which is connected as a segment of the conduit conveying the liquid. The vessel is provided with a valved outlet and is partitioned by a vertical baffle into coaxial chambers whose upper regions are vented to permit the escape of gas. The inner chamber receives turbulent downflowing liquid from the conduit and is sized to operate at a lower pressure than the conduit, thus promoting evolution of gas from the liquid. Lower zones of the two chambers are interconnected so that the downflowing liquid establishes liquid levels in both chambers. The liquid level in the outer chamber is comparatively calm, being to a large extent isolated from the turbulence in the inner chamber once the liquid in the outer chamber has risen above the liquid-introduction zone for that chamber. Lower and upper probes are provided in the outer chamber for sensing the liquid level therein at points above its liquid-introduction zone. An electrical circuit is connected to the probes to display the time required for the liquid level in the outer chamber to successively contact the lower and upper probes. The average rate of flow through the conduit can be determined from the above-mentioned time and the vessel volume filled by the liquid during that time.
Flowmeter for determining average rate of flow of liquid in a conduit
Kennerly, J.M.; Lindner, G.M.; Rowe, J.C.
1981-04-30
This invention is a compact, precise, and relatively simple device for use in determining the average rate of flow of a liquid through a conduit. The liquid may be turbulent and contain bubbles of gas. In a preferred embodiment, the flowmeter includes an electrical circuit and a flow vessel which is connected as a segment of the conduit conveying the liquid. The vessel is provided with a valved outlet and is partitioned by a vertical baffle into coaxial chambers whose upper regions are vented to permit the escape of gas. The inner chamber receives turbulent downflowing liquid from the conduit and is sized to operate at a lower pressure than the conduit, thus promoting evolution of gas from the liquid. Lower zones of the two chambers are interconnected so that the downflowing liquid establishes liquid levels in both chambers. The liquid level in the outer chamber is comparatively calm, being to a large extent isolated from the turbulence in the inner chamber once the liquid in the outer chamber has risen above the liquid-introduction zone for that chamber. Lower and upper probes are provided in the outer chamber for sensing the liquid level therein at points above its liquid-introduction zone. An electrical circuit is connected to the probes to display the time required for the liquid level in the outer chamber to successively contact the lower and upper probes. The average rate of flow through the conduit can be determined from the above-mentioned time and the vessel volume filled by the liquid during that time.
Cortical shell-liquid core model for passive flow of liquid-like spherical cells into micropipets.
Yeung, A; Evans, E
1989-01-01
Many nonadherent cells exist as spheres in suspension and when sucked into pipets, deform continuously like liquids within the fixed surface area limitation of a plasma membrane envelope. After release, these cells eventually recover their spherical form. Consequently, pipet aspiration test provides a useful method to assay the apparent viscosity of such cells. For this purpose, we have analyzed the inertialess flow of a liquid-like model cell into a tube at constant suction pressure. The cell is modeled as a uniform liquid core encapsulated by a distinct cortical shell. The method of analysis employs a variational approach that minimizes errors in boundary conditions defined by the equations of motion for the cortical shell where the trial functions are exact solutions for the flow field inside the liquid core. For the particular case of an anisotropic liquid cortex with persistent tension, we have determined universal predictions for flow rate scaled by the ratio of excess pressure (above the threshold established by the cortical tension) and core viscosity which is the reciprocal of the dynamic resistance to entry. The results depend on pipet to cell size ratio and a parameter that characterizes the ratio of viscous flow resistance in the cortex to that inside the cytoplasmic core. The rate of entry increases markedly as the pipet size approaches the outer segment diameter of the cell. Viscous dissipation in the cortex strongly influences the entry flow resistance for small tube sizes but has little effect for large tubes. This indicates that with sufficient experimental resolution, measurement of cell entry flow with different-size pipets could establish both the cortex to cell dissipation ratio as well as the apparent viscosity of the cytoplasmic core. Images FIGURE 1 PMID:2752083
Drainage of the air film during drop impact on flowing liquid films
NASA Astrophysics Data System (ADS)
Che, Zhizhao; Matar, Omar
2015-11-01
Immediately upon the impact of a droplet on a liquid or a solid, a thin air cushion is formed by trapping air beneath the droplet. The drainage of the air film is critical in determining the eventual outcome of the impact. Here we propose a model to study the drainage of the gas film between a droplet and a flowing liquid film. The effects of a wide range of parameters influencing the drainage process are studied, such as the fluid viscosities, the surface tension, the velocity of the droplet, the velocity of the liquid film. The results show that the tangential movement of the liquid film can delay the drainage of the air film and promote the bouncing of droplets. This confirms our previous experimental results, which show that during the impact of droplets on flow liquid films, the probability of bouncing increases with the Reynolds number of the liquid film. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.
On the Motion of an Annular Film in Microgravity Gas-Liquid Flow
NASA Technical Reports Server (NTRS)
McQuillen, John B.
2002-01-01
Three flow regimes have been identified for gas-liquid flow in a microgravity environment: Bubble, Slug, and Annular. For the slug and annular flow regimes, the behavior observed in vertical upflow in normal gravity is similar to microgravity flow with a thin, symmetrical annular film wetting the tube wall. However, the motion and behavior of this film is significantly different between the normal and low gravity cases. Specifically, the liquid film will slow and come to a stop during low frequency wave motion or slugging. In normal gravity vertical upflow, the film has been observed to slow, stop, and actually reverse direction until it meets the next slug or wave.
Keska, Jerry K.; Hincapie, Juan; Jones, Richard
2011-02-15
In the steady-state flow of a heterogeneous mixture such as an air-liquid mixture, the velocity and void fraction are space- and time-dependent parameters. These parameters are the most fundamental in the analysis and description of a multiphase flow. The determination of flow patterns in an objective way is extremely critical, since this is directly related to sudden changes in spatial and temporal changes of the random like characteristic of concentration. Flow patterns can be described by concentration signals in time, amplitude, and frequency domains. Despite the vital importance and countless attempts to solve or incorporate the flow pattern phenomena into multiphase models, it has still been a very challenging topic in the scientific community since the 1940's and has not yet reached a satisfactory solution. This paper reports the experimental results of the impact of fluid viscosity on flow patterns for two-phase flow. Two-phase flow was created in laboratory equipment using air and liquid as phase medium. The liquid properties were changed by using variable concentrations of glycerol in water mixture which generated a wide-range of dynamic viscosities ranging from 1 to 1060 MPa s. The in situ spatial concentration vs. liquid viscosity and airflow velocity of two-phase flow in a vertical ID=50.8 mm pipe were measured using two concomitant computer-aided measurement systems. After acquiring data, the in situ special concentration signals were analyzed in time (spatial concentration and RMS of spatial concentration vs. time), amplitude (PDF and CPDF), and frequency (PSD and CPSD) domains that documented broad flow pattern changes caused by the fluid viscosity and air velocity changes. (author)
Bubble Formation from Wall Orifice in Liquid Cross-Flow Under Low Gravity
NASA Technical Reports Server (NTRS)
Nahra, Henry K.; Kamotani, Y.
2000-01-01
Two-phase flows present a wide variety of applications for spacecraft thermal control systems design. Bubble formation and detachment is an integral part of the two phase flow science. The objective of the present work is to experimentally investigate the effects of liquid cross-flow velocity, gas flow rate, and orifice diameter on bubble formation in a wall-bubble injection configuration. Data were taken mainly under reduced gravity conditions but some data were taken in normal gravity for comparison. The reduced gravity experiment was conducted aboard the NASA DC-9 Reduced Gravity Aircraft. The results show that the process of bubble formation and detachment depends on gravity, the orifice diameter, the gas flow rate, and the liquid cross-flow velocity. The data are analyzed based on a force balance, and two different detachment mechanisms are identified. When the gas momentum is large, the bubble detaches from the injection orifice as the gas momentum overcomes the attaching effects of liquid drag and inertia. The surface tension force is much reduced because a large part of the bubble pinning edge at the orifice is lost as the bubble axis is tilted by the liquid flow. When the gas momentum is small, the force balance in the liquid flow direction is important, and the bubble detaches when the bubble axis inclination exceeds a certain angle.
Bubble formation during horizontal gas injection into downward-flowing liquid
NASA Astrophysics Data System (ADS)
Bai, Hua; Thomas, Brian G.
2001-12-01
Bubble formation during gas injection into turbulent downward-flowing water is studied using high-speed videos and mathematical models. The bubble size is determined during the initial stages of injection and is very important to turbulent multiphase flow in molten-metal processes. The effects of liquid velocity, gas-injection flow rate, injection hole diameter, and gas composition on the initial bubble-formation behavior have been investigated. Specifically, the bubble-shape evolution, contact angles, size, size range, and formation mode are measured. The bubble size is found to increase with increasing gas-injection flow rate and decreasing liquid velocity and is relatively independent of the gas injection hole size and gas composition. Bubble formation occurs in one of four different modes, depending on the liquid velocity and gas flow rate. Uniform-sized spherical bubbles form and detach from the gas injection hole in mode I for a low liquid speed and small gas flow rate. Modes III and IV occur for high-velocity liquid flows, where the injected gas elongates down along the wall and breaks up into uneven-sized bubbles. An analytical two-stage model is developed to predict the average bubble size, based on realistic force balances, and shows good agreement with measurements. Preliminary results of numerical simulations of bubble formation using a volume-of-fluid (VOF) model qualitatively match experimental observations, but more work is needed to reach a quantitative match. The analytical model is then used to estimate the size of the argon bubbles expected in liquid steel in tundish nozzles for conditions typical of continuous casting with a slide gate. The average argon bubble sizes generated in liquid steel are predicted to be larger than air bubbles in water for the same flow conditions. However, the differences lessen with increasing liquid velocity.
Recent developments of analysis for hydrodynamic flow of nematic liquid crystals
Lin, Fanghua; Wang, Changyou
2014-01-01
The study of hydrodynamics of liquid crystals leads to many fascinating mathematical problems, which has prompted various interesting works recently. This article reviews the static Oseen–Frank theory and surveys some recent progress on the existence, regularity, uniqueness and large time asymptotic of the hydrodynamic flow of nematic liquid crystals. We will also propose a few interesting questions for future investigations. PMID:25332384
Steady flow and evaporation of a volatile liquid in a wedge
NASA Astrophysics Data System (ADS)
Markos, Mulugeta; Ajaev, Vladimir S.; Homsy, G. M.
2006-09-01
We develop a lubrication-type model of a liquid flow in a wedge in the limit of small capillary numbers and negligible gravity. Liquid flows under the action of capillary pressure gradients and thermocapillary stresses, and evaporates due to heating from the solid walls on which a constant axial temperature gradient is imposed. Steady vapor-liquid interface shapes are found for different wedge angles and material properties of the liquid. In the limit of weak evaporation (e.g., in the adiabatic region of a heat pipe) and negligible Marangoni number, the flow rate is the same in all cross sections and can be controlled by changing the wedge angle. We find the wedge angle that results in the maximum value of the flow rate for a given contact angle. For finite evaporation rates, both the flow rate and the amount of liquid in each cross section along the wedge decrease until the point of dry-out is reached. The location of the dry-out point is studied as a function of evaporation conditions. Somewhat counterintuitively, we find that the dry-out point shifts toward the region of higher temperature as evaporation intensity is increased. The effect of thermocapillary stresses on the vapor-liquid interface shape is also investigated in the limit of negligible evaporation. Since thermocapillarity generally opposes the capillary flow, it leads to shorter wetted lengths. The implications of the results for design and optimization of micro heat pipes are discussed.
Dispersiveness of Liquid Droplets Sprayed with Cocurrent Gas Flow
NASA Astrophysics Data System (ADS)
Arkhipov, Vladimir; Antonnikova, Alexandra; Basalayev, Sergey; Zharova, Irina; Orlov, Sergey
2016-02-01
Pneumohydraulic stand, equipped with a set of aerosol systems laser diagnostics devices, are presented. The results of experimental measurements of the aerosol liquid-drop size distribution in the ejection nozzle spray pattern are provided.
Komatsu, Takanori; Ohishi, Risa; Shino, Amiu; Kikuchi, Jun
2016-05-10
Improved signal identification for biological small molecules (BSMs) in a mixture was demonstrated by using multidimensional NMR on samples from (13) C-enriched Rhododendron japonicum (59.5 atom%) cultivated in air containing (13) C-labeled carbon dioxide for 14 weeks. The resonance assignment of 386 carbon atoms and 380 hydrogen atoms in the mixture was achieved. 42 BSMs, including eight that were unlisted in the spectral databases, were identified. Comparisons between the experimental values and the (13) C chemical shift values calculated by density functional theory supported the identifications of unlisted BSMs. Tracing the (13) C/(12) C ratio by multidimensional NMR spectra revealed faster and slower turnover ratios of BSMs involved in central metabolism and those categorized as secondary metabolites, respectively. The identification of BSMs and subsequent flow analysis provided insight into the metabolic systems of the plant. PMID:27060701
NASA Astrophysics Data System (ADS)
Erwee, M. W.; Reynolds, Q. G.; Zietsman, J. H.
2016-03-01
Furnace tap-holes vary in design depending on the type of furnace and process involved, but they share one common trait: The tap-hole must be opened and closed periodically. In general, tap-holes are plugged with refractory clay after tapping, thereby stopping the flow of molten material. Once a furnace is ready to be tapped, drilling and/or lancing with oxygen are typically used to remove tap-hole clay from the tap-hole. Lancing with oxygen is an energy-intensive, mostly manual process, which affects the performance and longevity of the tap-hole refractory material as well as the processes inside the furnace. Computational modeling offers an opportunity to gain insight into the possible effects of oxygen lancing on various aspects of furnace operation.
NASA Astrophysics Data System (ADS)
Erwee, M. W.; Reynolds, Q. G.; Zietsman, J. H.
2016-06-01
Furnace tap-holes vary in design depending on the type of furnace and process involved, but they share one common trait: The tap-hole must be opened and closed periodically. In general, tap-holes are plugged with refractory clay after tapping, thereby stopping the flow of molten material. Once a furnace is ready to be tapped, drilling and/or lancing with oxygen are typically used to remove tap-hole clay from the tap-hole. Lancing with oxygen is an energy-intensive, mostly manual process, which affects the performance and longevity of the tap-hole refractory material as well as the processes inside the furnace. Computational modeling offers an opportunity to gain insight into the possible effects of oxygen lancing on various aspects of furnace operation.
NASA Astrophysics Data System (ADS)
Campbell, Bryce; Hendrickson, Kelli; Liu, Yuming; Subramani, Hariprasad
2014-11-01
For gas-liquid flows through pipes and channels, a flow regime (referred to as slug flow) may occur when waves form at the interface of a stratified flow and grow until they bridge the pipe diameter trapping large elongated gas bubbles within the liquid. Slug formation is often accompanied by strong nonlinear wave-wave interactions, wave breaking, and gas entrainment. This work numerically investigates the fully nonlinear interfacial evolution of a two-phase density/viscosity stratified flow through a horizontal channel. A Navier-Stokes flow solver coupled with a conservative volume-of-fluid algorithm is use to carry out high resolution three-dimensional simulations of a turbulent gas flowing over laminar (or turbulent) liquid layers. The analysis of such flows over a range of gas and liquid Reynolds numbers permits the characterization of the interfacial stresses and turbulent flow statistics allowing for the development of physics-based models that approximate the coupled interfacial-turbulent interactions and supplement the heuristic models built into existing industrial slug simulators.
Two-Dimensional Numerical Simulation of Boiling Two-Phase Flow of Liquid Nitrogen
NASA Astrophysics Data System (ADS)
Ishimoto, Jun; Oike, Mamoru; Kamijo, Kenjiro
Two-dimensional characteristics of the boiling two-phase flow of liquid nitrogen in a duct flow are numerically investigated to contribute to the further development of new high-performance cryogenic engineering applications. First, the governing equations of the boiling two-phase flow of liquid nitrogen based on the unsteady drift-flux model are presented and several flow characteristics are numerically calculated taking account the effect of cryogenic flow states. Based on the numerical results, a two-dimensional structure of the boiling two-phase flow of liquid nitrogen is shown in detail, and it is found that the phase change of liquid nitrogen occurs in quite a short time interval compared with that of two-phase pressurized water at high temperature. Next, it is clarified that the distributions of pressure and the void fraction in a two-phase flow show a tendency different from those of fluids at room temperature because of the decrease in sound velocity due to large compressibility and the rapid phase change velocity in a cryogenic two-phase mixture flow. According to these numerical results, the fundamental characteristics of the cryogenic two-phase flow are predicted. The numerical results obtained will contribute to advanced cryogenic industrial applications.
NASA Astrophysics Data System (ADS)
Yamamoto, T.; Takagi, Y.; Okano, Y.; Dost, S.
2013-08-01
NASA Astronaut Dr. Pettit carried out a thermocapillary flow experiment onboard the International Space Station in 2003. In this experiment a thin water film containing milk powder was formed in a stainless-steel wire ring. Heating a section of the ring by a soldering iron induced in the water film a thermocapillary flow towards the heated section of the ring (outward flow: cold to hot). This flow was in the opposite direction of the usually observed thermocapillary flows (inward flow: hot to cold). To shed light on this interesting phenomenon observed in the space experiment, we have conducted a three-dimensional numerical simulation study. Simulation results showed that the film geometry of the water film is a key factor determining flow direction and flow strength. When the liquid film free surfaces are convex, i.e., the water film volume is larger than that when the free surfaces are flat, an outward flow develops in the film as observed in the space experiment. However, when the free surfaces are concave, the simulation predicts an inward flow.
Automatic liquid crystal thermography for transient heat transfer measurements in hypersonic flow
NASA Astrophysics Data System (ADS)
Babinsky, H.; Edwards, J. A.
1996-08-01
A technique has been developed to measure surface heat transfer on windtunnel models in hypersonic flow based on the colour response of encapsulated thermochromic liquid crystals. The method supplies results of a superior spatial resolution at experimental uncertainties comparable to traditional methods. The approach is different from other liquid crystal applications in several key areas. It combines the calibration of the liquid crystal coating with the actual mesurement and therefore allows for an efficient experiment. The method is automated in most steps involved. Results are shown for the flow over an axisymmetric compression corner at Mach 5 and compared with surface thermocouple measurements.
NASA Astrophysics Data System (ADS)
Godard, G.; Paranthoen, P.; Gonzalez, M.
Anisotropic small-scale injection of a scalar (e.g. heat) in a turbulent medium can be performed by means of a small-diameter line source as already done in a turbulent plane jet and a turbulent boundary layer (Rosset et al., Phys. Fluids 13, 3729, 2001). In such conditions, however, experiment is revealed delicate especially, as regard to temperature gradient measurements in the near-field of the source. In the present study, we get rid of previous difficulties by setting up the heated line source in a simpler flow namely, a Bénard-von Kármán street. Under this situation, owing to a phase reference, the history of the instantaneous temperature gradient can be scrutinized from the vicinity of the source. Gradient statistics (second-order mo- ments, skewness, kurtosis ...) is derived which allows us to follow the evolution of anisotropy downstream of the line source. Alignment of temperature gradient with respect to strain principal axes is also analyzed. This experiment provides a precise knowledge of the way in which a scalar gradient evolves under the combined actions of strain, vorticity and molecular diffusion.
NASA Astrophysics Data System (ADS)
Bennett, Thomas P.; Proctor, Matthew B.; Kaczmarek, Malgosia; D'Alessandro, Giampaolo
2015-09-01
Optical light modulation in photorefractive liquid crystal cells depends strongly on the relative voltage drop across the photoconductive and liquid crystal layers. This quantity can be estimated using the Voltage Transfer Function, a generalization of the standard cross polarized intensity measurements. Another advantage of this new measurement technique is that we can use it to estimate dynamical parameters of the liquid crystal and of the device, either through simple black-box models or using a full Ericksen-Leslie theory. In this latter case we can obtain estimates of some of the viscosities of the liquid crystal.
Operating experience using venturi flow meters at liquid helium temperature
Wu, K.C.
1992-06-01
Experiences using commercial venturi to measure single phase helium flow near 4 K (degree Kelvin) for cooling superconducting magnets have been presented. The mass flow rate was calculated from the differential pressure and the helium density evaluated from measured pressure and temperature. The venturi flow meter, with a full range of 290 g/s (0.29 Kg/s) at design conditions, has been found to be reliable and accurate. The flow measurements have been used, with great success, for evaluating the performance of a cold centrifugal compressor, the thermal acoustic heat load of a cryogenic system and the cooling of a superconducting magnet after quench.
Operating experience using venturi flow meters at liquid helium temperature
Wu, K.C.
1992-01-01
Experiences using commercial venturi to measure single phase helium flow near 4 K (degree Kelvin) for cooling superconducting magnets have been presented. The mass flow rate was calculated from the differential pressure and the helium density evaluated from measured pressure and temperature. The venturi flow meter, with a full range of 290 g/s (0.29 Kg/s) at design conditions, has been found to be reliable and accurate. The flow measurements have been used, with great success, for evaluating the performance of a cold centrifugal compressor, the thermal acoustic heat load of a cryogenic system and the cooling of a superconducting magnet after quench.
Hsu, Sen-ming; Chang, Hung-chun
2008-12-22
To effectively investigate the fundamental characteristics of two-dimensional (2D) photonic crystals (PCs) with arbitrary 3D material anisotropy under the out-of-plane wave propagation, we establish a full-vectorial finite element method based eigenvalue algorithm to perform related analysis correctly. The band edge diagrams can be conveniently constructed from the band structures of varied propagation constants obtained from the algorithm, which is helpful for the analysis and design of photonic ban gap (PBG) fibers. Several PCs are analyzed to demonstrate the correctness of this numerical model. Our analysis results for simple PCs are checked with others' ones using different methods, including the transfer matrix method, the finite-difference frequency-domain (FDFD) method, and the plane-wave expansion method. And the validity of those for the most complex PC with arbitrary 3D anisotropy is supported by related liquid-crystal-filled PBG fiber mode analysis, which demonstrates the dependence of transmission properties on the PBGs, employing a full-vectorial finite element beam propagation method (FE-BPM). PMID:19104565
Characteristics of flow, mixing and chemical reaction of two liquids in a thin gap
NASA Astrophysics Data System (ADS)
Nagatsu, Yuichiro; Ueda, Toshihisa
1999-11-01
Characteristics of flow, mixing and chemical reaction of two liquids in a thin gap (less than 1mm) are examined experimentally. The flow in a thin gap is formed in a Hele-Shaw cell, consisting of two parallel closely spaced glass plates. A less viscous liquid is injected at a constant volumetric flow rate into the cell that is filled with a more viscous liquid. Experiments are done varying the viscosities of liquids, the concentrations of reactants, the injection flow rate and the gap of the cell respectively. The viscosities of viscous liquids are varied by weight concentrations of water and glycerin. As reactants, Ferric Nitrate(‡V)(Fe(NO3)) is used for the more viscous liquid and Potassium Thiocyanate(KSCN) for the less one. (Chemical reaction used in this study is as follows ; Fe3+(yellow)+KSCN(colorless)\\x81¨[FeSCN]2+(bloody red) ) Regions of reactants and product are identified by the difference of the colors of reactants and product. The images of the patterns of flow, mixing and chemical reaction photographed by a video camera are analyzed. The region of product changes remarkably as the gap of the cell is decreased. Additional experimental results will be presented at the meeting.
Enhanced critical heat flux by capillary driven liquid flow on the well-designed surface
NASA Astrophysics Data System (ADS)
Kim, Dong Eok; Park, Su Cheong; Yu, Dong In; Kim, Moo Hwan; Ahn, Ho Seon
2015-07-01
Based on the unique design of the surface morphology, we investigated the effects of gravity and capillary pressure on Critical heat flux (CHF). The micro-structured surfaces for pool boiling tests were comprised with both the rectangular cavity and microchannel structures. The microcavity structures could intrinsically block the liquid flow by capillary pressure effect, and the capillary flow into the boiling surface was one-dimensionally induced only through the microchannel region. Thus, we could clearly establish the relationship between the CHF and capillary wicking flow. The driving potentials for the liquid inflow can be classified into the hydrostatic head by gravitational force, and the capillary pressure induced by the interactions of vapor bubbles, liquid film, and surface solid structures. Through the analysis of the experimental data and visualization of vapor bubble behaviors, we present that the liquid supplement to maintain the nucleate boiling regime in pool boiling condition is governed by the gravitational pressure head and capillary pressure effect.
Method of driving liquid flow at or near the free surface using magnetic microparticles
Snezhko, Oleksiy; Aronson, Igor; Kwok, Wai-Kwong; Belkin, Maxim V.
2011-10-11
The present invention provides a method of driving liquid flow at or near a free surface using self-assembled structures composed of magnetic particles subjected to an external AC magnetic field. A plurality of magnetic particles are supported at or near a free surface of liquid by surface tension or buoyancy force. An AC magnetic field traverses the free surface and dipole-dipole interaction between particles produces in self-assembled snake structures which oscillate at the frequency of the traverse AC magnetic field. The snake structures independently move across the free surface and may merge with other snake structures or break up and coalesce into additional snake structures experiencing independent movement across the liquid surface. During this process, the snake structures produce asymmetric flow vortices across substantially the entirety of the free surface, effectuating liquid flow across the free surface.
NASA Astrophysics Data System (ADS)
Jin, Haibo; Yuhuan, Han; Suohe, Yang
2009-02-01
Electrical resistance tomography (ERT) is an advanced and new detecting technique that can measure and monitor the parameters of two-phase flow on line, such as gas-liquid bubble column. It is fit for the industrial process where the conductible medium serves as the disperse phase to present the key bubble flow characteristics in multi-phase medium. Radial variation of the gas holdup and mean holdups are investigated in a 0.160 m i. d. bubble column using ERT with two axial locations (Plane 1 and Plane 2). In all the experiments, air was used as the gas phase, tap water as liquid phase, and a series of experiments were done by adding KCl, ethanol, oil sodium, and glycerol to change liquid conductivity, liquid surface tension and viscosity. The superficial gas velocity was varied from 0.02 to 0.2 m/s. The effect of conductivity, surface tension, viscosity on the mean holdups and radial gas holdup distribution is discussed. The results showed that the gas holdup decrease with the increase of surface tension and increase with the increase of viscosity. Meanwhile, the settings of initial liquid conductivity slightly influence the gas holdup values, and the experimental data increases with the increase of the initial setting values in the same conditions.
Rapid flow fractionation of particles combining liquid and particulate dielectrophoresis
NASA Technical Reports Server (NTRS)
King, Michael R. (Inventor); Lomakin, Oleg (Inventor); Jones, Thomas B. (Inventor); Ahmed, Rajib (Inventor)
2007-01-01
Rapid, size-based, deposition of particles from liquid suspension is accomplished using a nonuniform electric field created by coplanar microelectrode strips patterned on an insulating substrate. The scheme uses the dielectrophoretic force both to distribute aqueous liquid containing particles and, simultaneously, to separate the particles. Size-based separation is found within nanoliter droplets formed along the structure after voltage removal. Bioparticles or macromolecules of similar size can also be separated based on subtle differences in dielectric property, by controlling the frequency of the AC current supplied to the electrodes.
Ohira, Shin-Ichi; Toda, Kei
2006-01-01
Accurate liquid flow control is important in most chemical analyses. In this work, the measurement of liquid flow in microliters per minute was performed, and feedback control of the flow rate was examined. The flow sensor was arranged on a channel made in a polydimethylsiloxane (PDMS) block. The center of the channel was cooled by a miniature Peltier device, and the change in temperature balance along the channel formed by the flow was measured by two temperature sensors. Using this flow sensor, feedback flow control was examined with two pumping methods. One was the electroosmotic flow method, made by applying a high voltage (HV) between the reagent and waste reservoirs; the other was the piezo valve method, in which a micro-valve-seat was fabricated in a PDMS cavity with a silicone diaphragm. The latter was adopted for a micro gas analysis system (microGAS) for measuring atmospheric H2S and SO2. The obtained baselines were stable, and better limits of detection were obtained. PMID:16429774
Numerical simulation of cavitating flow of liquid helium in a pipe using multi-fluid model
NASA Astrophysics Data System (ADS)
Ishimoto, J.; Oike, M.; Kamijo, K.
2002-05-01
The two-dimensional characteristics of the cavitating flow of liquid helium in a pipe are numerically investigated to realize the further development and high performance of new cryogenic engineering applications. First, the governing equations of the cavitating flow of liquid helium based on the unsteady thermal nonequilibrium multi-fluid model are presented and several flow characteristics are numerically calculated, taking into account the effect of superfluidity. Based on the numerical results, the two-dimensional structure of the turbulent cavitating flow of liquid helium passing through the orifice is shown in detail, and it is also found that the phase transition of the normal fluid to the superfluid and the generation of superfluid counterflow against normal fluid flow are conspicuous in the large gas phase volume fraction region where the liquid to gas phase change actively occurs. Furthermore, it is clarified that the mechanism of the He I to He II phase transition caused by the temperature decrease is due to the deprivation of latent heat for vaporization from the liquid phase. According to these theoretical results, the fundamental characteristics of the cryogenic cavitating flow are predicted.
The effects of bubbles on the structure of upward gas-liquid flow
NASA Astrophysics Data System (ADS)
Gubaidulin, D. A.; Snigerev, B. A.
2016-01-01
The paper presents the results of study of the local structure of turbulent gas-liquid flow in vertical pipe. A mathematical model based on the use of Eulerian description for both phases taking into account the action of different forces of interfacial interaction. Special attention is paid to the development of approaches for the simulation of polydispersed bubbly flows taking into account processes of coagulation and fragmentation. Comparison of simulation results with experimental data showed that the developed approach allows to obtain detailed information about the structures of turbulent gas-liquid flows, the distribution of bubbles by size.
Flow-driven transition and associated velocity profiles in a nematic liquid-crystal cell.
Jewell, S A; Cornford, S L; Yang, F; Cann, P S; Sambles, J R
2009-10-01
The alignment properties and distribution of flow speed during Poiseuille flow through a microchannel of a nematic liquid crystal in a cell with homeotropic surface alignment has been measured using a combination of conoscopy, fluorescence confocal polarizing microscopy, and time-lapse imaging. Two topologically distinct director profiles, with associated fluid velocity fields, are found to exist with the preferred state dictated by the volumetric flow rate of the liquid crystal. The results show excellent agreement with model data produced using the Ericksen-Leslie nematodynamics theory. PMID:19905324
Convective heat and mass transfer during the evaporation of a liquid into a gas flow
NASA Astrophysics Data System (ADS)
Boiarshinov, B. F.; Volchkov, E. P.; Terekhov, V. I.
1985-10-01
Heat and mass transfer processes associated with liquid evaporation are analyzed for adiabatic and nonadiabatic conditions. Experimental data are then presented on heat and mass transfer during the evaporation of water and ethyl alcohol from a porous surface. It is shown that heat and mass transfer under conditions of evaporation can be described by using expressions for flow past a 'dry' wall. A diagram is presented for determining the magnitudes of additional heat sources in the case of nonadiabatic evaporation. Finally, the effect of various factors, such as temperature, flow humidity, and liquid type, on heat and mass transfer during evaporation is analyzed for laminar and turbulent flows.
Pumping of dielectric liquids using non-uniform-field induced electrohydrodynamic flow
NASA Astrophysics Data System (ADS)
Kim, Wonkyoung; Chun Ryu, Jae; Kweon Suh, Yong; Hyoung Kang, Kwan
2011-11-01
We present a method of pumping dielectric (or non-polar) liquids. The pumping method relies on the electrohydrodynamic flow generated by field dependent electrical conductivity (Onsager effect). Adding a small amount of polar liquid increases the field-dependency of conductivity. Applying either dc or ac voltage produces a fast and regular flow around electrodes. Flow speed is proportional to cube of electric-field strength and inversely to applied frequency. The experimental results agreed well with numerical analysis based on our theoretical model.
Performance analysis on solid-liquid mixed flow in a centrifugal pump
NASA Astrophysics Data System (ADS)
Ning, C.; Wang, Y.
2016-05-01
In order to study the solid-liquid mixed flow hydraulic characteristics of centrifugal pump, the Pro/E software was used for three-dimensional modeling of centrifugal pump chamber. By using the computational fluid dynamics software CFX, the numerical simulation calculation of solid-liquid two-phase flow within whole flow passage of centrifugal pump was conducted. Aim at different particle diameters, the Reynolds-averaged N-S equations with the RNG k-Ɛ turbulence model and SIMPLEC algorithm were used to simulate the two-phase flow respectively on the condition of different volume fraction. The influence of internal flow characteristic on pump performance was analyzed. On the conditions of different particle diameter and different volume fraction, the turbulence kinetic energy and particle concentration are analyzed. It can be found that the erosion velocity ratio on the flow channel wall increases along with the increasing of the volume fraction
NASA Astrophysics Data System (ADS)
Noirez, L.; Lapp, A.
1997-01-01
We determine the structure and conformation of side-chain liquid-crystalline polymers subjected to shear flow in the vicinity of the smectic phase by neutron scattering on the velocity gradient plane. Below the nematic-smectic transition we observe a typical liquid-crystal behavior; the smectic layers slide, leading to a main-chain elongation parallel to the velocity direction. In contrast, a shear applied above the transition induces a tilted main-chain conformation which is typical for polymer behavior.
The effect of surfactant on stratified and stratifying gas-liquid flows
NASA Astrophysics Data System (ADS)
Heiles, Baptiste; Zadrazil, Ivan; Matar, Omar
2013-11-01
We consider the dynamics of a stratified/stratifying gas-liquid flow in horizontal tubes. This flow regime is characterised by the thin liquid films that drain under gravity along the pipe interior, forming a pool at the bottom of the tube, and the formation of large-amplitude waves at the gas-liquid interface. This regime is also accompanied by the detachment of droplets from the interface and their entrainment into the gas phase. We carry out an experimental study involving axial- and radial-view photography of the flow, in the presence and absence of surfactant. We show that the effect of surfactant is to reduce significantly the average diameter of the entrained droplets, through a tip-streaming mechanism. We also highlight the influence of surfactant on the characteristics of the interfacial waves, and the pressure gradient that drives the flow. EPSRC Programme Grant EP/K003976/1.
2D-Crystal-Based Functional Inks.
Bonaccorso, Francesco; Bartolotta, Antonino; Coleman, Jonathan N; Backes, Claudia
2016-08-01
The possibility to produce and process graphene, related 2D crystals, and heterostructures in the liquid phase makes them promising materials for an ever-growing class of applications as composite materials, sensors, in flexible optoelectronics, and energy storage and conversion. In particular, the ability to formulate functional inks with on-demand rheological and morphological properties, i.e., lateral size and thickness of the dispersed 2D crystals, is a step forward toward the development of industrial-scale, reliable, inexpensive printing/coating processes, a boost for the full exploitation of such nanomaterials. Here, the exfoliation strategies of graphite and other layered crystals are reviewed, along with the advances in the sorting of lateral size and thickness of the exfoliated sheets together with the formulation of functional inks and the current development of printing/coating processes of interest for the realization of 2D-crystal-based devices. PMID:27273554
Time and flow-direction responses of shear-styress-sensitive liquid crystal coatings
NASA Technical Reports Server (NTRS)
Reda, Daniel C.; Muraqtore, J. J.; Heinick, James T.
1994-01-01
Time and flow-direction responses of shear-stress liquid crystal coatings were exploresd experimentally. For the time-response experiments, coatings were exposed to transient, compressible flows created during the startup and off-design operation of an injector-driven supersonic wind tunnel. Flow transients were visualized with a focusing schlieren system and recorded with a 100 frame/s color video camera.
Reduced Gravity Gas and Liquid Flows: Simple Data for Complex Problems
NASA Technical Reports Server (NTRS)
McQuillen, John; Motil, Brian
2001-01-01
While there have been many studies for two-phase flow through straight cylindrical tubes, more recently, a new group of studies have emerged that examine two-phase flow through non-straight, non-cylindrical geometries, including expansions, contractions, tees, packed beds and cyclonic separation devices. Although these studies are still, relatively speaking, in their infancy, they have provided valuable information regarding the importance of the flow momentum, and the existence of liquid dryout due to sharp comers in microgravity.
Note: Ultrasonic liquid flow meter for small pipes.
Yu, Yang; Zong, Guanghua
2012-02-01
An ultrasonic flow meter for small pipes is presented. For metal pipe diameter smaller than 10 mm, clamp-on ultrasonic contrapropagation flow meters may encounter difficulties if cross talk or the short acoustic path contributes to large uncertainty in transit time measurement. Axial inline flow meters can avoid these problems, but they may introduce other problems if the transducer port is not properly positioned. Three types of pipe connecting tees are compared using the computational fluid dynamics (CFD) method. CFD shows the 45° tee has more uniform velocity distribution over the measuring section. A prototype flow meter using the 45° tee was designed and tested. The zero flow experiment shows the flow meter has a maximum of 0.002 m∕s shift over 24 h. The flow meter is calibrated by only 1 meter factor. After calibration, inaccuracy lower than 0.1% of reading was achieved in the laboratory, for a measuring range from 15 to 150 g∕s (0.29 to 2.99 m∕s; Re = 2688 to 26,876). PMID:22380141
Note: Ultrasonic liquid flow meter for small pipes
NASA Astrophysics Data System (ADS)
Yu, Yang; Zong, Guanghua
2012-02-01
An ultrasonic flow meter for small pipes is presented. For metal pipe diameter smaller than 10 mm, clamp-on ultrasonic contrapropagation flow meters may encounter difficulties if cross talk or the short acoustic path contributes to large uncertainty in transit time measurement. Axial inline flow meters can avoid these problems, but they may introduce other problems if the transducer port is not properly positioned. Three types of pipe connecting tees are compared using the computational fluid dynamics (CFD) method. CFD shows the 45° tee has more uniform velocity distribution over the measuring section. A prototype flow meter using the 45° tee was designed and tested. The zero flow experiment shows the flow meter has a maximum of 0.002 m/s shift over 24 h. The flow meter is calibrated by only 1 meter factor. After calibration, inaccuracy lower than 0.1% of reading was achieved in the laboratory, for a measuring range from 15 to 150 g/s (0.29 to 2.99 m/s; Re = 2688 to 26 876).
Numerical modeling of gas-liquid flows in mini- and microchannels
NASA Astrophysics Data System (ADS)
Guzei, D. V.; Minakov, A. V.; Pryazhnikov, M. I.; Dekterev, A. A.
2015-01-01
The paper presents the results of testing a methodology for calculating two-phase flows in mini- and microchannels. The numerical methodology is based on the known fluid-in-cell method (VOF method) and the CSF procedure to account for surface tension forces. Solutions of several test problems of two-phase flow in microchannels, including the water-oil emulsion flow and gas-liquid flow in microchannels of the T-type and the stationary slug flow in a circular minichannel, were considered with the aid of this technique. Comparisons of numerical results with experimental data were carried out. A good agreement between the results was obtained.
NASA Astrophysics Data System (ADS)
Talmage, Gita; Walker, John S.; Brown, Samuel H.; Sondergaard, Neal A.
1993-09-01
In homopolar motors and generators, large dc electric currents pass through the sliding electrical contacts between rotating copper disks (rotors) and static copper surfaces shrouding the rotor tips (stators). A liquid metal in the small radial gap between the rotor tip and concentric stator surface can provide a low-resistance, low-drag electrical contact. Since there is a strong magnetic field in the region of the electrical contacts, there are large electromagnetic body forces on the liquid metal. The primary, azimuthal motion consists of simple Couette flow, plus an electromagnetically driven flow with large extremes of the azimuthal velocity near the rotor corners. The secondary flow involves the radial and axial velocity components, is driven by the centrifugal force associated with the primary flow, and is opposed by the electromagnetic body force, so that the circulation varies inversely as the square of the magnetic-field strength. Three flow regimes are identified as the angular velocity Ω of the rotor is increased. For small Ω, the primary flow is decoupled from the secondary flow. As Ω increases, the secondary flow begins to convect the azimuthal-velocity peaks radially outward, which in turn changes the centrifugal force driving the secondary flow. At some critical value of Ω, the flow becomes periodic through the coupling of the primary and secondary flows. The azimuthal-velocity peaks begin to move radially in and out with an accompanying oscillation in the secondary-flow strength.
Microprocessor Based Temperature Control of Liquid Delivery with Flow Disturbances.
ERIC Educational Resources Information Center
Kaya, Azmi
1982-01-01
Discusses analytical design and experimental verification of a PID control value for a temperature controlled liquid delivery system, demonstrating that the analytical design techniques can be experimentally verified by using digital controls as a tool. Digital control instrumentation and implementation are also demonstrated and documented for…
Fiber optic liquid mass flow sensor and method
NASA Technical Reports Server (NTRS)
Korman, Valentin (Inventor); Gregory, Don Allen (Inventor); Wiley, John T. (Inventor); Pedersen, Kevin W. (Inventor)
2010-01-01
A method and apparatus are provided for sensing the mass flow rate of a fluid flowing through a pipe. A light beam containing plural individual wavelengths is projected from one side of the pipe across the width of the pipe so as to pass through the fluid under test. Fiber optic couplers located at least two positions on the opposite side of the pipe are used to detect the light beam. A determination is then made of the relative strengths of the light beam for each wavelength at the at least two positions and based at least in part on these relative strengths, the mass flow rate of the fluid is determined.
Liquid flow and distribution in unsaturated porous media
NASA Technical Reports Server (NTRS)
Alexander, J. Iwan
2004-01-01
Flow and transport in permeable or porous media and microchannels occurs in a variety of situations in micro- and reduced-gravity environments, many of them associated with environmental control and life support systems. While the role of gravity is limited, due to the typically small size scales associated permeable media, gravity, at the very least, affects the overall disposition of fluid in a macroscopic system. This presentation will discuss examples where the absence of gravity affects flow and phase distribution in selected examples of unsaturated flow and transport of heat and mass in porous media and microchannels that are pertinent to spacecraft systems.
An ultrasonic flowmeter for measuring dynamic liquid flow
NASA Technical Reports Server (NTRS)
Carpini, T. D.; Monteith, J. H.
1978-01-01
A novel oscillating pipe system was developed to provide dynamic calibration wherein small sinusoidal signals with amplitudes of 0.5 to 10% of the steady-state flow were added to the steady-state flow by oscillating the flowmeter relative to the fixed pipes in the flow system. Excellent agreement was obtained between the dynamic velocities derived from an accelerometer mounted on the oscillating pipe system and those sensed by the flowmeter at frequencies of 7, 19, and 30 Hz. Also described were the signal processing techniques used to retrieve the small sinusoidal signals which were obscured by the fluid turbulence.
Pressure drop in fully developed, duct flow of dispersed liquid-vapor mixture at zero gravity
NASA Technical Reports Server (NTRS)
Sridhar, K. R.; Chao, B. T.; Soo, S. L.
1990-01-01
The dynamics of steady, fully developed dispersed liquid-vapor flow in a straight duct at 0-g is simulated by flowing water containing n-butyl benzoate droplets. Water and benzoate are immiscible and have identical density at room temperature. The theoretical basis of the simulation is given. Experiments showed that, for a fixed combined flow rate of water and benzoate, the frictional pressure drop is unaffected by large changes in the volume fraction of benzoate drops and their size distribution. Measured power spectra of the static wall pressure fluctuations induced by the turbulent water-benzoate flow also revealed that their dynamics is essentially unaltered by the presence of the droplets. These experimental findings, together with the theoretical analysis, led to the conclusion that the pressure drop in fully developed, dispersed liquid-vapor flow in straight ducts of constant cross section at 0-g is identical to that due to liquid flowing alone at the same total volumetric flow rate of the liquid-vapor mixture and, therefore, can be readily determined.
Spatio-temporal evolution of interfacial instabilities in vertical gas-liquid flows
NASA Astrophysics Data System (ADS)
Schmidt, Patrick; Valluri, Prashant; Ó Náraigh, Lennon; Lucquiaud, Mathieu
2014-11-01
Vertical gas-liquid flows are characteristic for process engineering and widely employed in various technical applications. However, the dynamic behaviour of the liquid interface in such flows is still not fully understood. We focus in our work on characterising the interfacial instability as well as associated interfacial waves in vertical laminar-laminar gas-liquid flows over a wide range of parameters covering different flow regimes, i.e. counter-current, zero-interface velocity (loading) and partial-to-full liquid flow reversal (flooding). High-resolution direct numerical simulations using the TPLS flow solver (http://sourceforge.net/projects/tpls/) reveal the existence of weakly nonlinear interfacial waves, which are in good agreement with Stuart-Landau theory. These waves travel down- or upstream, depending on the flow regime. Furthermore, spatio-temporal linear stability analysis indicates the occurrence of absolute instability within the investigated parameter range. DNS is used to analyse this feature in more detail whereby agreement with linear theory has been established.
Two phase flow of liquids in a narrow gap: Phase interference and hysteresis
NASA Astrophysics Data System (ADS)
Raza, Salim; Hejazi, S. Hossein; Gates, Ian D.
2016-07-01
Co-current flow of two immiscible liquids, such as oil and water in a planar fracture, exhibits nonlinear structures which become important in many natural and engineering systems such as subsurface flows, multiphase flows in lubrication joints, and coating flows. In this context, co-current flow of oil and water with variable rates is experimentally studied in a Hele-Shaw cell, various flow regimes are classified, and relative permeabilities for the phases are analysed thoroughly. Similar to multiphase pipe flows, multiphase flow in planar gaps shows various flow regimes, each having different flow rate/pressure gradient behaviour. As well as recovering the known results in the immiscible displacements in Hele-Shaw cell where the fluid-fluid interface remains stable/unstable for favorable/adverse viscosity ratios, it is found that the co-current flow of two fluids with different viscosities results in three distinct flow regimes. Before breakthrough of non-wetting phase, i.e, water, a "linear displacement" flow regime initially establishes at very low water injection rates. This stable movement turns into a "fingering advancement" flow regime at high water flow rates and Saffman-Taylor instability develops normal to the direction of the flow. After the breakthrough, a "droplet formation" flow regime is identified where the droplets of wetting phase, oil, are trapped in the water phase. For subsurface flow applications, we quantify these regimes through relative permeability curves. It is reported that as the water flow rate increases, the relative permeabilities and flow channels become smooth and regular. This behaviour of relative permeability and saturations shows dominance of capillary forces at low flow rates and viscous forces at higher flow rates. Variable injection rates provide the interface structures for both drainage and imbibition process, where the wetting phase saturation decreases and increases respectively. It is shown that relative permeability
Chromatographic sample collection from two-phase (gas+liquid) flows.
Bruno, Thomas J; Windom, Bret C
2011-12-01
A particularly challenging sample presentation in analytical chemistry is a flowing stream that consists of both a gas and liquid phase, combined with the common situation in which a reliable analysis is needed for both phases, separately. In these cases, the vapor and liquid must be physically separated (without change to either), before the individual phases can be collected and analyzed. It is not possible to analyze two-phase flows otherwise. Although the two phases are at equilibrium, it is imperative that no liquid contaminate the vapor, and no vapor be entrained in the liquid at a given temperature and pressure. In this paper, we describe a simple on-line device that can individually separate and collect the vapor and liquid phases of a two-phase flow. The apparatus, which we call P(2)SC, uses an adaptation of the branch point separator, with vapor collection done downstream in a metal bellows. The liquid collection is done in a length of Teflon tube. The separated vapor and liquid phases are then easily transferred into any desired analytical instrument with a syringe, although any sample introduction method, such as a valve, could be used as well. We discuss the application of this device with a stream of thermally stressed rocket kerosene. PMID:22036084
Cycle-Induced Flow and Transport in an Alveolus Partially Filled with Liquid
NASA Astrophysics Data System (ADS)
Wei, Hsien-Hung; Benintendi, Steven W.; Halpern, David; Grotberg, James B.
2001-11-01
The flow and transport in an alveolus are of fundamental importance to partial liquid ventilation, surfactant transport, pulmonary drug administration, and gene therapy. A simplified model is developed for alveolar liquid lining undergoing cyclic stretching which mimics breathing motions. A thin, viscous film coats an extensible slot with small aspect ratio and strained amplitude. We apply scaling analysis and asymptotic theory to describe the interface profile and surfactant distribution during the oscillation cycle for either insoluble or soluble surfactants. The flow consists of two distinct regimes: a near-parallel flow region and a non-parallel flow, end region near the slot pinned wall. Non-zero cycle-averaged flows are shown and their turning directions near the pinned wall depend on the parameters of the system. We also model the case when the liquid is partially filled in the alveolus and has a comparable thickness to the size of the alveolus. The surfactant-free case is first investigated. By assuming a spherical interface due to small capillary number, we solve the Stokes flow analytically in the toroidal coordinate system. For small liquid volume, the flow field is dominated by the normal velocity component while large liquid volume leads to vortex structures near the alveolar opening. The flow is zero cycle-averaged. However, when the interface is deformed away from a spherical shape or surfactants are present, a non-zero cycle-averaged flow is expected. The research is supported by grants NASA NAG3-2196, NIH HL41126 and HL64373.
NASA Astrophysics Data System (ADS)
Howard, J. A.; Walsh, P. A.
2014-07-01
This paper presents an investigation on the heat transfer characteristics associated with liquid-gas Taylor flows in mini channels incorporating microencapsulated phase change materials (MPCM). Taylor flows have been shown to result in heat transfer enhancements due to the fluid recirculation experienced within liquid slugs which is attributable to the alternating liquid slug and gas bubble flow structure. Microencapsulated phase change materials (MPCM) also offer significant potential with increased thermal capacity due to the latent heat required to cause phase change. The primary aim of this work was to examine the overall heat transfer potential associated with combining these two novel liquid cooling technologies. By investigating the local heat transfer characteristics, the augmentation/degradation over single phase liquid cooling was quantified while examining the effects of dimensionless variables, including Reynolds number, liquid slug length and gas void fraction. An experimental test facility was developed which had a heated test section and allowed MPCM-air Taylor flows to be subjected to a constant heat flux boundary condition. Infrared thermography was used to record high resolution experimental wall temperature measurements and determine local heat transfer coefficients from the thermal entrance point. 30.2% mass particle concentration of the MPCM suspension fluid was examined as it provided the maximum latent heat for absorption. Results demonstrate a significant reduction in experimental wall temperatures associated with MPCM-air Taylor flows when compared with the Graetz solution for conventional single phase coolants. Total enhancement in the thermally developed region is observed to be a combination of the individual contributions due to recirculation within the liquid slugs and also absorption of latent heat. Overall, the study highlights the potential heat transfer enhancements that are attainable within heat exchange devices employing MPCM
NASA Astrophysics Data System (ADS)
Jaworski, Michael Andrew
The Solid/Liquid Lithium Divertor experiment (SLiDE) has been designed, constructed and operated in order to determine the behavior of these liquid conductors in a magnetic field with imposed thermal gradients. Liquid lithium is chosen for its applicability to fusion systems as well as recent demonstrations of its ability to passively redistribute incident heat fluxes on the order of 50[MW/m2]. The lithium is contained within a stainless steel tray that is actively cooled and contains a set of temperature diagnostics for analysis of the heat, flux coming from the tray. The system is magnetized by a set of external magnets and a linear electron beam is used to create heat fluxes similar to those found in fusion divertors. Surface velocity of the liquid lithium is measured with a digital camera. A theory explaining the balance between thermoelectric magnetohydrodynamics and thero-capillary driven, free-surface flows in containers of arbitrary type in a magnetized environment has been developed. A new dimensionless group depending on the thermoelectric power of the liquid/container pair, the physical properties of the liquid and solid and the flow geometry has been found that determines which mechanism, TC or TEMHD, is the dominant effect in any given system. Experiments show that TEMHD dominates the flow in SLiDE, consistent with the theory governing these flows. This is verified by series of qualitative experiments, as well as quantitative comparison with theoretical flow predictions. This constitutes the first direct observation of TEMHD driven flow yet reported in the literature. Application of the developed theory indicates liquid lithium fusion systems will operate in a TEMHD dominated regime. Technologies suggested by the exploitation of TEMHD pumping are also presented.
Numerical simulation of cavitating flow of liquid helium in venturi channel
NASA Astrophysics Data System (ADS)
Ishimoto, Jun; Kamijo, Kenjiro
2003-01-01
The fundamental characteristics of the two-dimensional cavitating flow of liquid helium through a venturi channel near the lambda point are numerically investigated to realize the further development and high performance of new multi-phase superfluid cooling systems. First, the governing equations of the cavitating flow of liquid helium based on the unsteady thermal nonequilibrium multi-fluid model with generalized curvilinear coordinates system are presented, and several flow characteristics are numerically calculated, taking into account the effect of superfluidity. Based on the numerical results, the two-dimensional structure of the cavitating flow of liquid helium though venturi channel is shown in detail, and it is also found that the generation of superfluid counterflow against normal fluid flow based on the thermomechanical effect is conspicuous in the large gas phase volume fraction region where the liquid-to-gas phase change actively occurs. Furthermore, it is clarified that the mechanism of the He I to He II phase transition caused by the temperature decrease is due to the deprivation of latent heat for vaporization from the liquid phase.
Numerical Simulation of Cavitating Flow of Liquid Helium in a Vertical Converging-Diverging Nozzle
NASA Astrophysics Data System (ADS)
Ishimoto, J.; Kamijo, K.
2004-06-01
The basic characteristics of the two-dimensional cavitating flow of liquid helium through a vertical converging-diverging nozzle near the lambda point are numerically investigated to realize the further development and high performance of new multiphase He II cooling systems. First, the governing equations of the cavitating flow of liquid helium based on the unsteady thermal nonequilibrium multi-fluid model with generalized curvilinear coordinates system are presented, and several multiphase flow characteristics are numerically calculated, taking into account the effect of superfluidity. Based on the numerical results, the two-dimensional structure of the cavitating flow of liquid helium though a vertical converging-diverging nozzle is shown in detail, and it is also found that the generation of superfluid counterflow against normal fluid flow based on the thermomechanical effect is conspicuous in the large gas phase volume fraction region where the liquid to gas phase change actively occurs. Furthermore, it is clarified that the mechanism of the He I to He II phase transition caused by the temperature decrease is due to the deprivation of latent heat for vaporization from the liquid phase.
Numerical Analysis of Cavitating Flow of Liquid Helium inHorizontal Converging-Diverging Channel
NASA Astrophysics Data System (ADS)
Ishimoto, Jun; Kamijo, Kenjiro
The basic characteristics of the two-dimensional cavitating flow of liquid helium through a horizontal converging-diverging channel near the lambda point are numerically investigated to realize the further development and high performance of new multiphase superfluid cooling systems. First, the governing equations of the cavitating flow of liquid helium based on the unsteady thermal nonequilibrium multifluid model with generalized curvilinear coordinates system are presented, and several flow characteristics are numerically calculated, taking into account the effect of superfluidity. Based on the numerical results, the two-dimensional structure of the cavitating flow of liquid helium though horizontal converging-diverging channel is shown in detail, and it is also found that the generation of superfluid counterflow against normal fluid flow based on the thermo mechanical effect is conspicuous in the large gas phase volume fraction region where the liquid- to gas-phase change actively occurs. Furthermore, it is clarified that the mechanism of the He I to He II phase transition caused by the temperature decrease is due to the deprivation of latent heat for vaporization from the liquid phase.
Design and Fabrication of a MEMS Flow Sensor and Its Application in Precise Liquid Dispensing
Liu, Yaxin; Chen, Liguo; Sun, Lining
2009-01-01
A high speed MEMS flow sensor to enhance the reliability and accuracy of a liquid dispensing system is proposed. Benefitting from the sensor information feedback, the system can self-adjust the open time of the solenoid valve to accurately dispense desired volumes of reagent without any pre-calibration. First, an integrated high-speed liquid flow sensor based on the measurement of the pressure difference across a flow channel is presented. Dimensions of the micro-flow channel and two pressure sensors have been appropriately designed to meet the static and dynamic requirements of the liquid dispensing system. Experiments results show that the full scale (FS) flow measurement ranges up to 80 μL/s, with a nonlinearity better than 0.51% FS. Secondly, a novel closed-loop control strategy is proposed to calculate the valve open time in each dispensing cycle, which makes the system immune to liquid viscosity, pressure fluctuation, and other sources of error. Finally, dispensing results show that the system can achieve better dispensing performance, and the coefficient of variance (CV) for liquid dispensing is below 3% at 1 μL and below 4% at 100 nL. PMID:22408517
NASA Astrophysics Data System (ADS)
Chughtai, I. R.; Iqbal, W.; Din, G. U.; Mehdi, S.; Khan, I. H.; Inayat, M. H.; Jin, J. H.
2013-05-01
A gas-liquid Taylor bubble flow occurs in small diameter channels in which gas bubbles are separated by slugs of pure liquid. This type of flow regime is well suited for solid catalyzed gas-liquid reactors in which the reaction efficiency is a strong function of axial dispersion in the regions of pure liquid. This paper presents an experimental study of liquid phase axial dispersion in a Taylor bubble flow developed in a horizontal tube using high speed photography and radiotracer residence time distribution (RTD) analysis. A parametric dependence of axial dispersion on average volume fraction of gas phase was also investigated by varying the relative volumetric flow rates of the two phases. 137mBa produced from a 137Cs/137mBa radionuclide generator was used as radiotracer and measurements were made using the NaI(Tl) scintillation detectors. Validation of 137mBa in the form of barium chloride as aqueous phase radiotracer was also carried out. Axial Dispersion Model (ADM) was used to simulate the hydrodynamics of the system and the results of the experiment are presented. It was observed that the system is characterized by very high values of Peclet Number (Pe˜102) which reveals an approaching plug type flow. The experimental and model estimated values of mean residence times were observed in agreement with each other.
NASA Astrophysics Data System (ADS)
Weidman, P. D.; Kubitschek, J. P.; Medina, A.
2008-11-01
The stability of viscous rotating liquid columns and their application to rotating viscous liquid jets aligned under gravity is reviewed. Experiments on stable viscous fluid flow discharged from rotating vertical pipes exhibit very weak contraction. We present an elementary liquid jet analysis to understand this phenomenon. Indeed, our inviscid model of a slender rotating inviscid liquid jet shows that rotation suppresses contraction. Next we study the comparable problem for granular flow. Our model for noncohesive granular flow emanating from a vertical pipe rotating about its central axis, valid for sufficiently large rotation rate, shows that the granular profiles blossom rather than contract. The profiles of both the liquid and granular jets depend on the same dimensionless parameters—an exit Froude number Fr0 and an exit swirl parameter χ0. The limitations of both models are discussed. Experimental data for granular jet profiles compare well with the collision-free granular flow model in its range of applicability. A criterion for the rotation rate at which particles adjacent to the inner wall of the rotating pipe cease to flow is also given and compared to experiment.
Physical understanding of gas-liquid annular flow and its transition to dispersed droplets
NASA Astrophysics Data System (ADS)
Kumar, Parmod; Das, Arup Kumar; Mitra, Sushanta K.
2016-07-01
Transformation from annular to droplet flow is investigated for co-current, upward gas-liquid flow through a cylindrical tube using grid based volume of fluid framework. Three transitional routes, namely, orificing, rolling, and undercutting are observed for flow transformation at different range of relative velocities between the fluids. Physics behind these three exclusive phenomena is described using circulation patterns of gaseous phase in the vicinity of a liquid film which subsequently sheds drop leading towards transition. Orifice amplitude is found to grow exponentially towards the core whereas it propagates in axial direction in a parabolic path. Efforts have been made to fit the sinusoidal profile of wave structure with the numerical interface contour at early stages of orificing. Domination of gas inertia over liquid flow has been studied in detail at the later stages to understand the asymmetric shape of orifice, leading towards lamella formation and droplet generation. Away from comparative velocities, circulations in the dominant phase dislodge the drop by forming either a ligament (rolling) or a bag (undercut) like protrusion in liquid. Study of velocity patterns in the plane of droplet dislodge reveals the underlying physics behind the disintegration and its dynamics at the later stages. Using numerical phase distributions, rejoining of dislodged droplet with liquid film as post-rolling consequences has been also proposed. A flow pattern map showing the transitional boundaries based on the physical mechanism is constructed for air-water combination.
Interparticle Attraction in 2D Complex Plasmas
NASA Astrophysics Data System (ADS)
Kompaneets, Roman; Morfill, Gregor E.; Ivlev, Alexei V.
2016-03-01
Complex (dusty) plasmas allow experimental studies of various physical processes occurring in classical liquids and solids by directly observing individual microparticles. A major problem is that the interaction between microparticles is generally not molecularlike. In this Letter, we propose how to achieve a molecularlike interaction potential in laboratory 2D complex plasmas. We argue that this principal aim can be achieved by using relatively small microparticles and properly adjusting discharge parameters. If experimentally confirmed, this will make it possible to employ complex plasmas as a model system with an interaction potential resembling that of conventional liquids.
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.
Pool boiling enhancement through bubble induced convective liquid flow in feeder microchannels
NASA Astrophysics Data System (ADS)
Jaikumar, A.; Kandlikar, S. G.
2016-01-01
Bubbles departing from the nucleation sites induce a liquid flow from the bulk to the heated surface during pool boiling. Alternating the nucleating regions with non-nucleating regions facilitates separate liquid-vapor pathways for departing vapor bubbles and returning liquid. We explored an additional enhancement through liquid feeder channels on the heater surface directing the returning liquid towards the nucleating region. The nucleating bubbles were confined to the nucleating region as the returning liquid flow induced strong convective currents over the non-nucleating regions. In the best performing configuration, the nucleating regions were 0.5 mm wide, separated by non-nucleating regions of width 2.125 mm, which corresponded to the bubble departure diameter. The non-nucleating regions contained 0.5 mm wide feeder channels directing liquid towards the nucleating region. High speed images indicated distinct vapor columns over the nucleating regions with liquid channeled through the feeder channels. At higher heat fluxes, the strong liquid currents established over the feeder channels suppressed any undesirable nucleation in them keeping the separated vapor-liquid pathways functional. This enhancement technique resulted in a critical heat flux of 394 W/cm2 at a wall superheat of 5.5 °C which translated to a heat transfer coefficient of 713 kW/m2 °C. The additional surface area and high heat transfer coefficient due to microchannel flow in feeder channels, and the unobstructed surface available for the bubbles to expand over the prime heat transfer surface area before departing were seen to be responsible for their superior performance.
Bubble Generation in a Continuous Liquid Flow Under Reduced Gravity Conditions
NASA Technical Reports Server (NTRS)
Pais, Salvatore Cezar
1999-01-01
The present work reports a study of bubble generation under reduced gravity conditions for both co-flow and cross-flow configurations. Experiments were performed aboard the DC-9 Reduced Gravity Aircraft at NASA Glenn Research Center, using an air-water system. Three different flow tube diameters were used: 1.27, 1.9, and 2.54 cm. Two different ratios of air injection nozzle to tube diameters were considered: 0.1 and 0.2. Gas and liquid volumetric flow rates were varied from 10 to 200 ml/s. It was experimentally observed that with increasing superficial liquid velocity, the bubbles generated decreased in size. The bubble diameter was shown to increase with increasing air injection nozzle diameters. As the tube diameter was increased, the size of the detached bubbles increased. Likewise, as the superficial liquid velocity was increased, the frequency of bubble formation increased and thus the time to detach forming bubbles decreased. Independent of the flow configuration (for either single nozzle or multiple nozzle gas injection), void fraction and hence flow regime transition can be controlled in a somewhat precise manner by solely varying the gas and liquid volumetric flow rates. On the other hand, it is observed that uniformity of bubble size can be controlled more accurately by using single nozzle gas injection than by using multiple port injection, since this latter system gives rise to unpredictable coalescence of adjacent bubbles. A theoretical model, based on an overall force balance, is employed to study single bubble generation in the dynamic and bubbly flow regime. Under conditions of reduced gravity, the gas momentum flux enhances bubble detachment; however, the surface tension forces at the nozzle tip inhibits bubble detachment. Liquid drag and inertia can act either as attaching or detaching force, depending on the relative velocity of the bubble with respect to the surrounding liquid. Predictions of the theoretical model compare well with performed
Straathof, Natan J W; Su, Yuanhai; Hessel, Volker; Noël, Timothy
2016-01-01
In this protocol, we describe the construction and use of an operationally simple photochemical microreactor for gas-liquid photoredox catalysis using visible light. The general procedure includes details on how to set up the microreactor appropriately with inlets for gaseous reagents and organic starting materials, and it includes examples of how to use it to achieve continuous-flow preparation of disulfides or trifluoromethylated heterocycles and thiols. The reported photomicroreactors are modular, inexpensive and can be prepared rapidly from commercially available parts within 1 h even by nonspecialists. Interestingly, typical reaction times of gas-liquid visible light photocatalytic reactions performed in microflow are lower (in the minute range) than comparable reactions performed as a batch process (in the hour range). This can be attributed to the improved irradiation efficiency of the reaction mixture and the enhanced gas-liquid mass transfer in the segmented gas-liquid flow regime. PMID:26633128
Liquid-Liquid Displacement Flows in a Hele-Shaw Cell including Viscoplastic Effects
NASA Astrophysics Data System (ADS)
de Souza Mendes, Paulo R.; Varges, Priscilla R.
2008-07-01
Viscous fingering in non-Newtonian fluids in a rectangular Hele-Shaw cell is investigated. This cell is filled with aqueous solutions of carbopol in two different concentrations. A Newtonian mineral oil is then injected into the cell and the displacement is observed. A digital camera is used to capture images of the interface between the fluids during the flow. Applications include displacement of heavy crude oil in reservoirs. The main parameters that govern this flow are the viscosity ratio, the rheological capillary number, and the (dimensionless) flow rate. The interface shape is given for two different values of flow rate and viscosity ratio.
NASA Astrophysics Data System (ADS)
Wang, Jin; Ma, Jianyong; Zhou, Changhe
2014-11-01
A 3×3 high divergent 2D-grating with period of 3.842μm at wavelength of 850nm under normal incidence is designed and fabricated in this paper. This high divergent 2D-grating is designed by the vector theory. The Rigorous Coupled Wave Analysis (RCWA) in association with the simulated annealing (SA) is adopted to calculate and optimize this 2D-grating.The properties of this grating are also investigated by the RCWA. The diffraction angles are more than 10 degrees in the whole wavelength band, which are bigger than the traditional 2D-grating. In addition, the small period of grating increases the difficulties of fabrication. So we fabricate the 2D-gratings by direct laser writing (DLW) instead of traditional manufacturing method. Then the method of ICP etching is used to obtain the high divergent 2D-grating.
NASA Astrophysics Data System (ADS)
Dubovikova, N.; Karcher, C.; Kolesnikov, Y.
2016-07-01
Providing flow analysis in case of aggressive and hot liquids is a complicated task, especially when liquid's composition and, hence, its physical properties, are unknown. Contactless techniques are the most promising methods for liquid metal flow rate control and some of these methods are based on electromagnetic induction of breaking force acting on an electrically conductive fluid which is moving through a magnetic field. One of the techniques is time-of-flight Lorentz force velocimetry (LFV). By using the method one can estimate volumetric flow rate without knowing of electrical conductivity, magnitude of magnetic field or characteristic dimension. The most important and crucial challenge within the technique is detection of small fluctuations of Lorentz force value. In this article we will focus on application and investigation of time-of-flight LFV.
Self-Powered Triboelectric Micro Liquid/Gas Flow Sensor for Microfluidics.
Chen, Jie; Guo, Hengyu; Zheng, Jiangeng; Huang, Yingzhou; Liu, Guanlin; Hu, Chenguo; Wang, Zhong Lin
2016-08-23
Liquid and gas flow sensors are important components of the micro total analysis systems (μTAS) for modern analytical sciences. In this paper, we proposed a self-powered triboelectric microfluidic sensor (TMS) by utilizing the signals produced from the droplet/bubble via the capillary and the triboelectrification effects on the liquid/solid interface for real-time liquid and gas flow detection. By alternating capillary with different diameters, the sensor's detecting range and sensitivity can be adjusted. Both the relationship between the droplet/bubble and capillary size, and the output signal of the sensor are systematically studied. By demonstrating the monitoring of the transfusion process for a patient and the gas flow produced from an injector, it shows that TMS has a great potential in building a self-powered micro total analysis system. PMID:27490518
Magnetohydrodynamic generators using two-phase liquid-metal flows
NASA Technical Reports Server (NTRS)
Petrick, M.
1969-01-01
Two-phase flow generator cycle of a magnetohydrodynamic /MHD/ generator uses a working fluid which is compressible and treated as an expanding gas. The two-phase mixture passes from the heat source through the MHD generator, where the expansion process takes place and the electrical energy is extracted.
Modelling of evaporation of a dispersed liquid component in a chemically active gas flow
NASA Astrophysics Data System (ADS)
Kryukov, V. G.; Naumov, V. I.; Kotov, V. Yu.
1994-01-01
A model has been developed to investigate evaporation of dispersed liquids in chemically active gas flow. Major efforts have been directed at the development of algorithms for implementing this model. The numerical experiments demonstrate that, in the boundary layer, significant changes in the composition and temperature of combustion products take place. This gives the opportunity to more correctly model energy release processes in combustion chambers of liquid-propellant rocket engines, gas-turbine engines, and other power devices.
Handling of liquid holdup in Duyong two-phase flow pipeline system
Saad, M.R.; Singh, B. )
1988-01-01
This paper deals with the handling of liquids in the multi-phase flow pipeline system within Carigali's Duyong Offshore Gas Complex and the Onshore Gas Terminal, in Kerteh, Terongganu. The data and operations experience gathered necessitate changes to the operating procedures originally identified during the design phase. This is to ensure more efficient handling of liquid hold-up in the pipeline during low gas flowrates.
Immersed boundary method for the MHD flows of liquid metals
NASA Astrophysics Data System (ADS)
Grigoriadis, D. G. E.; Kassinos, S. C.; Votyakov, E. V.
2009-02-01
Wall-bounded magnetohydrodynamic (MHD hereafter) flows are of great theoretical and practical interest. Even for laminar cases, MHD simulations are associated with very high computational cost due to the resolution requirements for the Hartmann and side layers developing in the presence of solid obstacles. In the presence of turbulence, these difficulties are further compounded. Thus, MHD simulations in complex geometries are currently a challenge. The immersed boundary (IB hereafter) method is a reliable numerical tool for efficient hydrodynamic field simulations in arbitrarily geometries, but it has not yet been extended for MHD simulations. The present study forms the first attempt to apply the IB methodology for the computation of both the hydrodynamic and MHD fields. A consistent numerical methodology is presented that is appropriate for efficient 3D MHD simulations in geometrically complicated domains using cartesian flow solvers. For that purpose, a projection scheme for the electric current density is presented, based on an electric potential correction algorithm. A suitable forcing scheme for electric density currents in the vicinity of non-conducting immersed surfaces is also proposed. The proposed methodology has been first extensively tested for Hartmann layers in fully-developed and developing channel and duct flows at Hartmann numbers Ha=500-2000. In order to demonstrate the potential of the method, the three-dimensional MHD flow around a circular cylinder at Reynolds number Re=200 is also presented. The effects of grid resolution and variable arrangement on the simulation accuracy and consistency were examined. When compared with existing numerical or analytic solutions, excellent agreement was found for all the cases considered. The proposed projection and forcing schemes for current densities were found capable of satisfying the charge conservation law in the presence of immersed non-conducting boundaries. Finally, we show how the proposed
The Discrete Multi-Hybrid System for the Simulation of Solid-Liquid Flows
Alexiadis, Alessio
2015-01-01
This study proposes a model based on the combination of Smoothed Particle Hydrodynamics, Coarse Grained Molecular Dynamics and the Discrete Element Method for the simulation of dispersed solid-liquid flows. The model can deal with a large variety of particle types (non-spherical, elastic, breakable, melting, solidifying, swelling), flow conditions (confined, free-surface, microscopic), and scales (from microns to meters). Various examples, ranging from biological fluids to lava flows, are simulated and discussed. In all cases, the model captures the most important features of the flow. PMID:25961561
Suppressing turbulence and enhancing liquid suspension flow in pipelines with electrorheology
NASA Astrophysics Data System (ADS)
Tao, R.; Gu, G. Q.
2015-01-01
Flows through pipes, such as crude oil through pipelines, are the most common and important method of transportation of fluids. To enhance the flow output along the pipeline requires reducing viscosity and suppressing turbulence simultaneously and effectively. Unfortunately, no method is currently available to accomplish both goals simultaneously. Here we show that electrorheology provides an efficient solution. When a strong electric field is applied along the flow direction in a small section of pipeline, the field polarizes and aggregates the particles suspended inside the base liquid into short chains along the flow direction. Such aggregation breaks the rotational symmetry and makes the fluid viscosity anisotropic. In the directions perpendicular to the flow, the viscosity is substantially increased, effectively suppressing the turbulence. Along the flow direction, the viscosity is significantly reduced; thus the flow along the pipeline is enhanced. Recent field tests with a crude oil pipeline fully confirm the theoretical results.
A visual study of radial inward choked flow of liquid nitrogen.
NASA Technical Reports Server (NTRS)
Hendricks, R. C.; Simoneau, R. J.; Hsu, Y. Y.
1973-01-01
Data and high speed movies were acquired on pressurized subcooled liquid nitrogen flowing radially inward through a 0.0076 cm gap. The stagnation pressure ranged from 0.7 to 4 MN/sq m. Steady radial inward choked flow appears equivalent to steady choked flow through axisymmetric nozzles. Transient choked flows through the radial gap are not uniform and the discharge pattern appears as nonuniform impinging jets. The critical mass flow rate data for the transient case appear different from those for the steady case. On the mass flow rate vs pressure map, the slope and separation of the isotherms appear to be less for transient than for steady radial choked flow.
Computation of turbulent flow in a thin liquid layer of fluid involving a hydraulic jump
NASA Technical Reports Server (NTRS)
Rahman, M. M.; Faghri, A.; Hankey, W. L.
1991-01-01
Numerically computed flow fields and free surface height distributions are presented for the flow of a thin layer of liquid adjacent to a solid horizontal surface that encounters a hydraulic jump. Two kinds of flow configurations are considered: two-dimensional plane flow and axisymmetric radial flow. The computations used a boundary-fitted moving grid method with a k-epsilon model for the closure of turbulence. The free surface height was determined by an optimization procedure which minimized the error in the pressure distribution on the free surface. It was also checked against an approximate procedure involving integration of the governing equations and use of the MacCormack predictor-corrector method. The computed film height also compared reasonably well with previous experiments. A region of recirculating flow was found to be present adjacent to the solid boundary near the location of the jump, which was caused by a rapid deceleration of the flow.
Magnetohydrodynamic flow in the liquid phase for a specific pool boiling scenario
NASA Astrophysics Data System (ADS)
Bühler, Leo
2002-11-01
In the EVOLVE concept for a nuclear fusion blanket a pool boiling scenario has been proposed where a number of permanent vertical vapour channels are formed in a horizontal layer of liquid lithium. Similar situations occur during laser beam welding where a relatively long vapour capillary is observed. The present analysis focuses on the flow of the electrically conducting liquid phase in the presence of a strong uniform horizontal magnetic field. The cross-section of vapour channels is circular if surface tension dominates magnetic forces. In the opposite case a stretching of the liquid vapour interface along magnetic field lines is observed and contours become possible where a major part of the interface is straight and aligned with the field. For strong magnetic fields the liquid flow exhibits several distinct subregions. Most of the liquid domain is occupied by inviscid cores. These are separated from each other by parallel layers that spread along the field lines which are tangential to the vapour channel. In one core, which is located between two parallel layers, the flow direction is preferentially oriented along magnetic field lines, while in the other cores the flow is perpendicular to the field.
Effects of Erosion Angle on Erosion Properties of Fe-B Alloy in Flowing Liquid Zinc
NASA Astrophysics Data System (ADS)
Liu, Guangzhu; Xing, Jiandong; Ma, Shengqiang; He, Yaling; Fu, Hanguang; Gao, Yuan; Wang, Yong; Wang, Yiran
2015-05-01
The effect of erosion angle on erosion behavior of the as-cast Fe-B alloy in flowing liquid zinc was investigated. The results show that the erosion rate of Fe-B alloy decreases linearly with increasing erosion angle. The erosion resistance of Fe-B alloy is better than that of 316L stainless steel, which is attributed to the favorable barrier effect of net-like Fe2B that resists erosion by flowing liquid zinc. Meanwhile, the ductile matrix can provide support in preventing borides from spalling and borides cause barrier effect on flowing liquid zinc during liquid zinc erosion, which shows a synergistic erosion-corrosion behavior between the matrix and borides. Moreover, an increase in erosion angle can cause a decrease in the removal effect of the flowing liquid zinc scouring component on the erosion compounds. Therefore, the quantity of erosion compounds increases at the erosion interface, weakening the mass transfer process and decreasing the erosion rate of the Fe-B alloy.
Modelling of liquid metal flow and oxide film defects in filling of aluminium alloy castings
NASA Astrophysics Data System (ADS)
Dai, X.; Jolly, M.; Yang, X.; Campbell, J.
2012-07-01
The liquid metal flow behaviours in different runner system designs have important effects on the mechanical strength of aluminium alloy castings. In this paper, a new model has been developed which is a two-dimensional program using a finite difference technique and the Marker and Cell (MAC) method to simulate the flow of liquid metal during filling a mould. In the program the Eulerian method has been used for the liquid metal flow, while the Oxide Film Entrainment Tracking Algorithm (OFET) method (a Lagrangian method) has been used to simulate the movement of the oxide film on the liquid metal surface or in the liquid metal flow. Several examples have been simulated and tested and the relevant results were obtained. These results were compared with measured bending strengths. It was found that the completed program was capable of simulating effectively the filling processes of different runner systems. The simulation results are consistent with the experiment. In addition, the program is capable of providing clearer images for predicting the distribution of the oxide film defects generated during filling a mould.
Experiments on Heat Transfer in a Thin Liquid Film Flowing Over a Rotating Disk
NASA Technical Reports Server (NTRS)
Sankaran, Subramanian (Technical Monitor); Ozar, B.; Cetegen, B. M.; Faghri, A.
2004-01-01
An experimental study of heat transfer into a thin liquid film on a rotating heated disk is described. Deionized water was introduced at the center of a heated. horizontal disk with a constant film thickness and uniform radial velocity. Radial distribution of the disk surface temperatures was measured using a thermocouple/slip ring arrangement. Experiments were performed for a range of liquid flow rates between 3.01pm and 15.01pm. The angular speed of the disk was varied from 0 rpm to 500 rpm. The local heat transfer coefficient was determined based on the heat flux supplied to the disk and the temperature difference between the measured disk surface temperature and the liquid entrance temperature onto the disk. The local heat transfer coefficient was seen to increase with increasing flow rate as well as increasing angular velocity of the disk. Effect of rotation on heat transfer was largest for the lower liquid flow rates with the effect gradually decreasing with increasing liquid flow rates. Semi-empirical correlations are presented in this study for the local and average Nusselt numbers.
Liquid fuel spray processes in high-pressure gas flow
NASA Technical Reports Server (NTRS)
Ingebo, R. D.
1986-01-01
Atomization of single liquid jets injected downstream in high pressure and high velocity airflow was investigated to determine the effect of airstream pressure on mean drop size as measured with a scanning radiometer. For aerodynamic - wave breakup of liquid jets, the ratio of orifice diameter D sub o to measured mean drop diameter D sub m which is assumed equal to D sub 32 or Sauter mean diameter, was correlated with the product of the Weber and Reynolds numbers WeRe and the dimensionless group G1/square root of c, where G is the gravitational acceleration, 1 the mean free molecular path, and square root of C the root mean square velocity, as follows; D sub o/D sub 32 = 1.2 (WeRe) to the 0.4 (G1/square root of c) to the 0.15 for values of WeRe 1 million and an airstream pressure range of 0.10 to 2.10 MPa.
Liquid fuel spray processes in high-pressure gas flow
NASA Technical Reports Server (NTRS)
Ingebo, R. D.
1985-01-01
Atomization of single liquid jets injected downstream in high pressure and high velocity airflow was investigated to determine the effect of airstream pressure on mean drop size as measured with a scanning radiometer. For aerodynamic - wave breakup of liquid jets, the ratio of orifice diameter D sub o to measured mean drop diameter D sub m which is assumed equal to D sub 32 or Sauter mean diameter, was correlated with the product of the Weber and Reynolds numbers WeRe and the dimensionless group G1/square root of c, where G is the gravitational acceleration, 1 the mean free molecular path, and square root of C the root mean square velocity, as follows; D sub o/D sub 32 = 1.2 (WeRe) to the 0.4 (G1/square root of c) to the 0.15 for values of WeRe 1 million and an airstream pressure range of 0.10 to 2.10 MPa.
Flow Characteristics of a Liquid Crystal Mixture in a Circular Pipe Electrode
NASA Astrophysics Data System (ADS)
Tsukiji, Tetsuhiro; Koyabu, Eitaro
A circular pipe electrode was developed to control the pressure and the flow rate of the ER(Electro-rheological) fluids by one of the authors. The shape of the electrode is a circular pipe and some parts of the inner surface of the pipe are the electrode. The diameter of the tube is 1mm and the four pairs of the electrode are used. In the present study a liquid crystal mixture is selected for a homogeneous ER fluid and the pressure drop of the circular pipe electrode is measured for the constant flow rates under application of the voltages. The voltages are added in the peripheral direction. The director which is the average direction of the molecular of the liquid crystal is perpendicular to the flow direction. On the other hands, numerical analysis of the electric fields and the flow in the circular pipe electrode is conducted and the relations between the flow rate and the pressure are obtained for various electric field intensities, which almost agree with experimental results. The emphasized point of the present flow analysis is assuming that the viscosity of a liquid crystal mixture distributes in the flow field. Furthermore the pulse-wave voltages are added to the electrodes to control the pressure drop using the pulse width modulation. It is found that the pressure can be controlled using the pulse width modulation in the some range of the parameters.
MHD Flow Of Walters' Liquid B Over A Nonlinearly Stretching Sheet
NASA Astrophysics Data System (ADS)
Siddheshwar, P. G.; Mahabaleshwar, U. S.; Chan, A.
2015-08-01
The paper discusses the boundary layer flow of a weak electrically conducting viscoelastic Walters' liquid B over a nonlinearly stretching sheet subjected to an applied transverse magnetic field, when the liquid far away from the surface is at rest. The stretching is assumed to be a quadratic function of the coordinate along the direction of stretching. An analytical expression is obtained for the stream function and velocity components as a function of the viscoelastic parameter, the Chandrasekhar number and stretching related parameters. The results have possible technological applications in liquid based systems involving stretchable materials.
A 3D CFD simulation of liquid flow in an ironmaking blast furnace
NASA Astrophysics Data System (ADS)
Shen, Yansong; Guo, Baoyu; Chew, Sheng; Austin, Peter; Yu, Aibing
2013-07-01
A three-dimensional CFX-based mathematical model is developed to describe the flow-heat transfer-chemical reactions behaviours of gas-solid-liquid phases in an ironmaking blast furnace (BF), where the raceway cavity is considered explicitly. The typical in-furnace phenomena of an operating blast furnace, in particular, the liquid flow in the lower part of a blast furnace is simulated in aspects of velocity and volume fraction. This model offers a cost-effective tool to understand and optimize blast furnace operation.
Evaluation of the viscosities of a liquid crystal model system by shear flow simulation
NASA Astrophysics Data System (ADS)
Sarman, Sten; Laaksonen, Aatto
2009-09-01
The three Miesowicz viscosities of a liquid crystal model system consisting of the Gay-Berne fluid have been obtained by shear flow simulations. The viscosities along an isochore have been followed starting in the nematic phase at high temperatures across the nematic-smectic A phase transition down to low temperatures in the smectic A phase. The relative magnitudes of the viscosities as a function of the structure of the liquid crystal are discussed. The viscosities obtained by the shear flow simulations agree very well with those obtained by Green-Kubo relations in a previous work.
Electrical impedance imaging in two-phase, gas-liquid flows: 1. Initial investigation
NASA Technical Reports Server (NTRS)
Lin, J. T.; Ovacik, L.; Jones, O. C.
1991-01-01
The determination of interfacial area density in two-phase, gas-liquid flows is one of the major elements impeding significant development of predictive tools based on the two-fluid model. Currently, these models require coupling of liquid and vapor at interfaces using constitutive equations which do not exist in any but the most rudimentary form. Work described herein represents the first step towards the development of Electrical Impedance Computed Tomography (EICT) for nonintrusive determination of interfacial structure and evolution in such flows.
Gas, liquids flow rates hefty at Galveston Bay discovery
Petzet, G.A.
1998-01-19
Extended flow tests indicate a large Vicksburg (Oligocene) gas, condensate, and oil field is about to be developed in western Galveston Bay. Internal estimates indicates that ultimate recovery from the fault block in which the discovery well was drilled could exceed 1 tcf of gas equivalent of proved, possible, and probable reserves. The paper discusses the test program for this field and other prospects in the Galveston Bay area.
Impact of Gas-liquid Two-phase Flow on Fluid Borne Noise
NASA Astrophysics Data System (ADS)
Taniwaki, Mitsuhiro; Shimomura, Nobuo
In pipe lines such as those found in refrigeration cycle, a gas-liquid two-phase flow may occur because of a pressure change in the pipe. This flow causes noise. A vapor phase ratio in a fluid and the behavior of bubbles are related to the outbreak of noise. This experimental study investigated the fluid borne noise caused by gas-liquid two-phase flow passing through a contracted section in horizontal pipe. In the experiment, sound pressure was measured for two purposes: to see the influence of the air-water ratio on sound pressure and to see the change in sound pressure when a single bubble passed through a contracted section in horizontal pipe. The experiment showed that the fluid borne noise of gas-liquid two-phase flow grew louder than that of a liquid single-phase flow. As for the frequency distribution of the fluid borne noise, the sound pressure level was higher in the high frequency band. Furthermore, the fluid borne noise grew louder with increasing bubble diameter.
Research on Gas-liquid Flow Rate Optimization in Foam Drilling
NASA Astrophysics Data System (ADS)
Gao, B. K.; Sun, D. G.; Jia, Z. G.; Huang, Z. Q.
2010-03-01
With the advantages of less gas consumption, higher carrying rocks ability, lower leakage and higher penetration rate, foam drilling is widely used today in petroleum industry. In the process of foam underbalanced drilling, the mixture of gas, liquid and cuttings flows upwards through the annular, so it is a typical gas-liquid-solid multi-phase flow. In order to protect the reservoir and avoid borehole wall collapsing during foam drilling, it is crucial to ensure that the bottom hole pressure is lower than the formation pressure and higher than the formation collapse pressure, and in the mean time, foam drilling fluid in the whole wellbore should be in the best foam quality stage in order to have sufficient capacity to carry cuttings. In this paper, main relations between bottom hole pressure and gas-liquid injecting rate are analyzed with the underbalanced multiphase flow models. And in order to obtain precise flow pattern and flow pressure, the whole well bore is spatial meshed and iterative method is used. So, a convenient safety window expressed by gas-liquid injecting rate is obtained instead of that by bottom hole pressure. Finally, a foam drilling example from a block in Yemen is presented; the drilling results show that this method is reliable and practical.