One-step preparation of superhydrophobic acrylonitrile-butadiene-styrene copolymer coating for ultrafast separation of water-in-oil emulsions.

PubMed

Deng, Wanshun; Long, Mengying; Zhou, Qiannan; Wen, Ni; Deng, Wenli

2018-02-01

Superhydrophobic membranes with opposite wettability toward water and oil are able to separate water-in-oil emulsions. By constructing porous and hierarchal-structured superhydrophobic coating on filter paper, we hope a quick separation process could be achieved due to the acceleration of both demulsification and penetration process. Here, superhydrophobic coatings were prepared by simply spraying environmental and cost-effective acrylonitrile-butadiene-styrene copolymer (ABS) colloid in dichloromethane onto filter paper. The morphologies and wettability of the obtained coatings were carefully studied. Moreover, the separation performances in dealing with various surfactant-stabilized water-in-oil emulsions (SSWOE) were also investigated to verify our hypothesis. The morphologies of the ABS coatings varied with its weight concentration in dichloromethane and they changed from porous and plain surface into porous and hierarchal-structured surface. Besides, the hydrophobicity of the above coatings varied form hydrophobic to superhydrophobic. Moreover, the resulted superhydrophobic membranes show great separation capability in separating various span 80-stabilized water-in-oil emulsions with oil filtrate purities larger than 99.90% and huge penetration fluxes whose maximum is over 13,000L/(m 2 h). Thus, we envision that such membrane can be a practical candidate in dealing with water-in-oil emulsions to obtain pure oils. Copyright © 2017 Elsevier Inc. All rights reserved.

[Comparison of essential oil enriched with ultrafiltration method and extraction method respectively from essential oil-in-water emulsion of Citri Reticulatae Pericarpium Viride by GC-MS].

PubMed

Yin, Ailing; Han, Zhifeng; Shen, Jie; Guo, Liwei; Cao, Guiping

2011-10-01

To study on the separation from essential oil-in-water emulsion of Citri Reticulatae Pericarpium Viride by ultrafiltration and acetoacetate extraction methods respectively, and the comparison of the oil yields and chemical compositions. Essential oil-in-water emulsion of Citri Reticulatae Pericarpium Viride was separated by ultrafiltration and acetoacetate extraction methods respectively, and the chemical compositions were analyzed and compared by GC-MS. Ultrafiltration method could enrich essential oil more and its chemical compositions were more similar to the essential oil prepared by steam distillation method. Ultrafiltration method is a good medium to separate essential oil from essential oil-in-water emulsion of Citri Reticulatae Pericarpium Viride.

Treatment methods for breaking certain oil and water emulsions

DOEpatents

Sealock, Jr., L. John; Baker, Eddie G.; Elliott, Douglas C.

1992-01-01

Disclosed are treatment methods for breaking emulsions of petroleum oil and salt water, fatty oil and water, and those resulting from liquefication of organic material. The emulsions are broken by heating to a predetermined temperature at or above about 200.degree. C. and pressurizing to a predetermined pressure above the vapor pressure of water at the predetermined temperature to produce a heated and pressurized fluid. The heated and pressurized fluid is contained in a single vessel at the predetermined temperature and pressure for a predetermined period of time to effectively separate the emulsion into substantially distinct first and second phases, the first phase comprising primarily the petroleum oil, the second phase comprising primarily the water. The first and second phases are separately withdrawn from the vessel at a withdraw temperature between about 200.degree. C. and 374.degree. C. and a withdraw pressure above the vapor pressure of water at the withdraw temperature. Where solids are present in the certain emulsions, the above described treatment may also effectively separate the certain emulsion into a substantially distinct third phase comprising primarily the solids.

Physical stability of R-(+)-Limonene emulsions stabilized by Ulva fasciata algae polysaccharide.

PubMed

Shao, Ping; Ma, Huiling; Qiu, Qiang; Jing, Weiping

2016-11-01

The physical stability of R-(+)-Limonene emulsions stabilized by Ulva fasciata polysaccharide (UFP) was investigated in this study. Emulsion physical stability was evaluated under different polysaccharide concentrations (1%-5%, wt/wt) and pH values (3.0-11.0). The stability of R-(+)-Limonene emulsions was demonstrated by droplet size distribution, rheological properties, zeta potential and visual phase separation. R-(+)-Limonene emulsions displayed monomodal droplet size distributions, high absolute values of zeta potential and good storage stability when 3% (wt/wt) UFP was used. The rheological properties and stability of R-(+)-Limonene emulsions appeared to be dependent on polysaccharide concentration. The emulsion stability was impacted by pH. Higher zeta potential (-52.6mV) and smaller mean droplet diameter (2.45μm) were achieved in neutral liquid environment (pH 7.0). Extreme acidity caused the flocculation of emulsions, which was manifested as phase separation, while emulsions were quite stable in an alkaline environment. Through comparing the stabilities of emulsions stabilized by different emulsifiers (i.e. UFP, GA and Gelatin), the result suggested that UFP was the best emulsifying agent among them. Copyright © 2016 Elsevier B.V. All rights reserved.

The application of pulse field gradient (PFG) NMR methods to characterize the efficiency of separation of water-in-crude oil emulsions.

PubMed

Marques, Debora Salomon; Sørland, Geir; Less, Simone; Vilagines, Regis

2018-02-15

Demulsification of water-in-crude oil emulsions is an essential and sometimes challenging procedure for crude oil processing facilities. Pulse field gradient (PFG) NMR techniques are known to monitor the dynamics of emulsion separation. This method has limitations that restrict its application to some crude oils. A comprehensive methodology applicable to all types of crude oil regardless of its viscosity, without assumptions, and providing a large number of data with fast measurements, is proposed in this paper. The coalescence and sedimentation of unstable emulsions was observed through simultaneous measurements of the evolution of the brine profile and droplet size distribution (DSD). Measurements of emulsions after stabilization, with and without the contribution of the free water layer, revealed the residual emulsified water quantity and location in the sample. A new, faster approach to separate the oil and water overlapping T 2 relaxation signals was demonstrated on real water-in-crude oil emulsions, using the root mean square displacement (RMSD) measured with the spoiler recovery and a loop of 13-interval pulsed field gradient stimulated echo (PFGSTE) oneshot sequences. The residual water within the crude oils after separation was determined and used to quantify the efficiency of the demulsifier used. Copyright © 2017 Elsevier Inc. All rights reserved.

Management of Vortices Trailing Flapped Wings via Separation Control

NASA Technical Reports Server (NTRS)

Greenblatt, David

2005-01-01

A pilot study was conducted on a flapped semi-span model to investigate the concept and viability of near-wake vortex management via separation control. Passive control was achieved by means of a simple fairing and active control was achieved via zero mass-flux blowing slots. Vortex sheet strength, estimated by integrating surface pressure ports, was used to predict vortex characteristics by means of inviscid rollup relations. Furthermore, vortices trailing the flaps were mapped using a seven-hole probe. Separation control was found to have a marked effect on vortex location, strength, tangential velocity, axial velocity and size over a wide range of angles of attack and control conditions. In general, the vortex trends were well predicted by the inviscid rollup relations. Manipulation of the separated flow near the flap edges exerted significant control over both outboard and inboard edge vortices while producing negligible lift excursions. Dynamic separation and attachment control was found to be an effective means for dynamically perturbing the vortex from arbitrarily long wavelengths down to wavelengths less than a typical wingspan. In summary, separation control has the potential for application to time-independent or time-dependent wake alleviation schemes, where the latter can be deployed to minimize adverse effects on ride-quality and dynamic structural loading.

Vortex dynamics and wall shear stress behaviour associated with an elliptic jet impinging upon a flat plate

NASA Astrophysics Data System (ADS)

Long, J.; New, T. H.

2016-07-01

Vortical structures and dynamics of a Re h = 2100 elliptic jet impinging upon a flat plate were studied at H/ d h = 1, 2 and 4 jet-to-plate separation distances. Flow investigations were conducted along both its major and minor planes using laser-induced fluorescence and digital particle image velocimetry techniques. Results show that the impingement process along the major plane largely consists of primary jet ring-vortex and wall-separated secondary vortex formations, where they subsequently separate from the flat plate at smaller H/ d h = 1 and 2 separation distances. Key vortex formation locations occur closer to the impingement point as the separation distance increases. Interestingly, braid vortices and rib structures begin to take part in the impingement process at H/ d h = 4 and wave instabilities dominate the flow field. In contrast, significantly more coherent primary and secondary vortices with physically larger vortex core sizes and higher vortex strengths are observed along the minor plane, with no signs of braid vortices and rib structures. Lastly, influences of these different flow dynamics on the major and minor plane instantaneous and mean skin friction coefficient levels are investigated to shed light on the effects of separation distance on the wall shear stress distributions.

Crosswind Shear Gradient Affect on Wake Vortices

NASA Technical Reports Server (NTRS)

Proctor, Fred H.; Ahmad, Nashat N.

2011-01-01

Parametric simulations with a Large Eddy Simulation (LES) model are used to explore the influence of crosswind shear on aircraft wake vortices. Previous studies based on field measurements, laboratory experiments, as well as LES, have shown that the vertical gradient of crosswind shear, i.e. the second vertical derivative of the environmental crosswind, can influence wake vortex transport. The presence of nonlinear vertical shear of the crosswind velocity can reduce the descent rate, causing a wake vortex pair to tilt and change in its lateral separation. The LES parametric studies confirm that the vertical gradient of crosswind shear does influence vortex trajectories. The parametric results also show that vortex decay from the effects of shear are complex since the crosswind shear, along with the vertical gradient of crosswind shear, can affect whether the lateral separation between wake vortices is increased or decreased. If the separation is decreased, the vortex linking time is decreased, and a more rapid decay of wake vortex circulation occurs. If the separation is increased, the time to link is increased, and at least one of the vortices of the vortex pair may have a longer life time than in the case without shear. In some cases, the wake vortices may never link.

Heat transfer simulation of unsteady swirling flow in a vortex tube

NASA Astrophysics Data System (ADS)

Veretennikov, S. V.; Piralishvili, Sh A.; Evdokimov, O. A.; Guryanov, A. I.

2018-03-01

Effectiveness of not-adiabatic vortex tube application in the cooling systems of gas turbine blades depends on characteristics of swirling flows formed in the energy separation chamber. An analysis of the flow structure in the vortex tube channels has shown a presence of a complex three-dimensional spiral vortex, formed under relatively high turbulence intensity and vortex core precession. This indicates the presence of a significant unsteady flow in the energy separation chamber of the vortex tube that has a great influence on convective heat transfer of the swirling flow to the inner surface of tube. The paper contains the results of investigation of gas dynamics and heat transfer in the vortex tube taking into account the flow unsteadiness.

Treatment method for emulsified petroleum wastes

DOEpatents

Sealock, Jr., L. John; Baker, Eddie G.; Elliott, Douglas C.

1990-01-01

An improved reclamation process for treating petroleum oil and water emulsions derived from producing or processing crude oil is disclosed. The process comprises heating the emulsion to a predetermined temperature at or above about 300.degree. C. and pressurizing the emulsion to a predetermined pressure above the vapor pressure of water at the predetermined temperature. The emulsion is broken by containing the heated and pressurized fluid within a vessel at the predetermined temperature and pressure for a predetermined period of time to effectively separate the emulsion into substantially distinct first, second and third phases. The three phases are then separately withdrawn from the vessel, preferably without any appreciable reduction in temperature and pressure, and at least above a withdraw temperature of about 300.degree. and above the vapor pressure of water at the withdraw temperature.

Elucidation of stabilizing oil-in-water Pickering emulsion with different modified maize starch-based nanoparticles.

PubMed

Ye, Fan; Miao, Ming; Jiang, Bo; Campanella, Osvaldo H; Jin, Zhengyu; Zhang, Tao

2017-08-15

The aim of present study was to study the medium-chain triacylglycerol-in-water (O/W) Pickering emulsion stabilized using different modified starch-based nanoparticles (octenylsuccinylation treated soluble starch nanoparticle, OSA-SSNP, and insoluble starch nanoparticle, ISNP). The major factors for affecting the system stability, rheological behaviour and microstructure of the emulsions were also investigated. The parameters of the O/W emulsions stabilized by OSA-SSNP or ISNP were selected as follows: 3.0% of starch nanoparticles concentration, 50% of MCT fraction and 7.0 of system pH. The rheological properties indicated that both emulsions displayed shear-thinning behaviour as a non-Newtonian fluid. For OSA-SSNP, the viscosities of the emulsion were higher than those of ISNP throughout shear rate range for the same condition. The plot of droplet size distribution for emulsion stabilized OSA-SSNP appeared as a single narrow peak, whereas a broader droplet size distribution with bimodal pattern was observed for emulsion stabilized ISNP. The microscopy results showed that both OSA-SSNP and ISNP were adsorbed at oil-water interface to form a barrier film and retard the phase separation. When emulsion was stored for 30d, no phase separation was detected for O/W emulsion, revealing high stability of emulsion stabilized by both OSA-SSNP and ISNP. Copyright © 2017 Elsevier Ltd. All rights reserved.

An experimental investigation of S-duct flow control using arrays of low-profile vortex generators

NASA Technical Reports Server (NTRS)

Reichert, Bruce A.; Wendt, Bruce J.

1993-01-01

An experimental investigation was undertaken to measure the effect of various configurations of low-profile vortex generator arrays on the flow in a diffusing S-duct. Three parameters that characterize the vortex generator array were systematically varied to determine their effect: (1) the vortex generator height; (2) the streamwise location of the vortex generator array; and (3) the vortex generator spacing. Detailed measurements of total pressure at the duct exit, surface static pressure, and surface flow visualization were gathered for each vortex generator configuration. These results are reported here along with total pressure recovery and distortion coefficients determined from the experimental data. Each array of vortex generators tested improved total pressure recovery. The configuration employing the largest vortex generators was the most effective in reducing total pressure recovery. No configuration of vortex generators completely eliminated the flow separation that naturally occurs in the S-duct, however the extent of the separated flow region was reduced.

Review of vortex tube expansion in vapour compression refrigeration system

NASA Astrophysics Data System (ADS)

Liu, Yefeng; Yu, Jun

2018-05-01

A vortex tube expansion device replacing the throttle valve is proposed to improve the efficiency of vapour compression refrigeration cycle by reducing the loss of irreversibility in expansion process. The vortex tube is well-suited for these applications because it is simple, compact, light, quiet. Thus, this paper presents an overview of the thermodynamic analysis of vapour compression refrigeration cycle with vortex tube expansion device using different refrigerants. The paper also reviews the experiments and the calculations presented in previous studies on temperature separation in the vortex tube. The temperature separation mechanism and the flow-field inside the vortex tubes is explored by measuring the pressure, velocity, and temperature fields.

Wake Vortex Research in the USA (WakeNet-USA)

NASA Technical Reports Server (NTRS)

Lang, Steve; Bryant, Wayne

2006-01-01

This viewgraph presentation reviews the cooperative work that FAA and NASA are engaged in to safely increase the capacity of the National Airspace System by studying the wake vortex operations. Wake vortex avoidance is a limiting factor in defining separation standards in the airport terminal area and could become a reducing separation standards in en route airspace.

Fabrication of Silica Nanospheres Coated Membranes: towards the Effective Separation of Oil-in-Water Emulsion in Extremely Acidic and Concentrated Salty Environments

PubMed Central

Chen, Yuning; Liu, Na; Cao, Yingze; Lin, Xin; Xu, Liangxin; Zhang, Weifeng; Wei, Yen; Feng, Lin

2016-01-01

A superhydrophilic and underwater superoleophobic surface is fabricated by simply coating silica nanospheres onto a glass fiber membrane through a sol-gel process. Such membrane has a complex framework with micro and nano structures covering and presents a high efficiency (more than 98%) of oil-in-water emulsion separation under harsh environments including strong acidic and concentrated salty conditions. This membrane also possesses outstanding stability since no obvious decline in efficiency is observed after different kinds of oil-in-water emulsions separation, which provides it candidate for comprehensive applicability. PMID:27597570

Process boundaries of irreversible scCO2 -assisted phase separation in biphasic whole-cell biocatalysis.

PubMed

Brandenbusch, Christoph; Glonke, Sebastian; Collins, Jonathan; Hoffrogge, Raimund; Grunwald, Klaudia; Bühler, Bruno; Schmid, Andreas; Sadowski, Gabriele

2015-11-01

The formation of stable emulsions in biphasic biotransformations catalyzed by microbial cells turned out to be a major hurdle for industrial implementation. Recently, a cost-effective and efficient downstream processing approach, using supercritical carbon dioxide (scCO2 ) for both irreversible emulsion destabilization (enabling complete phase separation within minutes of emulsion treatment) and product purification via extraction has been proposed by Brandenbusch et al. (2010). One of the key factors for a further development and scale-up of the approach is the understanding of the mechanism underlying scCO2 -assisted phase separation. A systematic approach was applied within this work to investigate the various factors influencing phase separation during scCO2 treatment (that is pressure, exposure of the cells to CO2 , and changes of cell surface properties). It was shown that cell toxification and cell disrupture are not responsible for emulsion destabilization. Proteins from the aqueous phase partially adsorb to cells present at the aqueous-organic interface, causing hydrophobic cell surface characteristics, and thus contribute to emulsion stabilization. By investigating the change in cell-surface hydrophobicity of these cells during CO2 treatment, it was found that a combination of catastrophic phase inversion and desorption of proteins from the cell surface is responsible for irreversible scCO2 mediated phase separation. These findings are essential for the definition of process windows for scCO2 -assisted phase separation in biphasic whole-cell biocatalysis. © 2015 Wiley Periodicals, Inc.

A vortex-filament and core model for wings with edge vortex separation

NASA Technical Reports Server (NTRS)

Pao, J. L.; Lan, C. E.

1982-01-01

A vortex filament-vortex core method for predicting aerodynamic characteristics of slender wings with edge vortex separation was developed. Semi-empirical but simple methods were used to determine the initial positions of the free sheet and vortex core. Comparison with available data indicates that: (1) the present method is generally accurate in predicting the lift and induced drag coefficients but the predicted pitching moment is too positive; (2) the spanwise lifting pressure distributions estimated by the one vortex core solution of the present method are significantly better than the results of Mehrotra's method relative to the pressure peak values for the flat delta; (3) the two vortex core system applied to the double delta and strake wings produce overall aerodynamic characteristics which have good agreement with data except for the pitching moment; and (4) the computer time for the present method is about two thirds of that of Mehrotra's method.

Integrated microfluidic system with simultaneous emulsion generation and concentration.

PubMed

Koppula, Karuna S; Fan, Rong; Veerapalli, Kartik R; Wan, Jiandi

2016-03-15

Because the size, size distribution, and concentration of emulsions play an important role in most of the applications, controlled emulsion generation and effective concentration are of great interest in fundamental and applied studies. While microfluidics has been demonstrated to be able to produce emulsion drops with controlled size, size distribution, and hierarchical structures, progress of controlled generation of concentrated emulsions is limited. Here, we present an effective microfluidic emulsion generation system integrated with an orifice structure to separate aqueous droplets from the continuous oil phase, resulting in concentrated emulsion drops in situ. Both experimental and simulation results show that the efficiency of separation is determined by a balance between pressure drop and droplet accumulation near the orifice. By manipulating this balance via changing flow rates and microfluidic geometry, we can achieve monodisperse droplets on chip that have a concentration as high as 80,000 drops per microliter (volume fraction of 66%). The present approach thus provides insights to the design of microfluidic device that can be used to concentrate emulsions (drops and bubbles), colloidal particles (drug delivery polymer particles), and biological particles (cells and bacteria) when volume fractions as high as 66% are necessary. Copyright © 2015 Elsevier Inc. All rights reserved.

Recent Emulsion Technologies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ariga, A.

2011-10-06

Emulsion technologies are very much developed in the last decade and still developing in both the emulsion gel and the data taking. Emulsion detectors are suitable for the neutrino experiments because they can distinguish all 3 flavors of neutrino. The OPERA experiment, a recent pillar in the emulsion experiments aiming at the first observation of the neutrino oscillation in CNGS beam in appearance mode, is running, showing the good capability to separate 3 flavor neutrino interactions. In this poster, the recent developments and prospects of the emulsions for the next generation experiments are reported.

Aeroelastic loads prediction for an arrow wing. Task 3: Evaluation of the Boeing three-dimensional leading-edge vortex code

NASA Technical Reports Server (NTRS)

Manro, M. E.

1983-01-01

Two separated flow computer programs and a semiempirical method for incorporating the experimentally measured separated flow effects into a linear aeroelastic analysis were evaluated. The three dimensional leading edge vortex (LEV) code is evaluated. This code is an improved panel method for three dimensional inviscid flow over a wing with leading edge vortex separation. The governing equations are the linear flow differential equation with nonlinear boundary conditions. The solution is iterative; the position as well as the strength of the vortex is determined. Cases for both full and partial span vortices were executed. The predicted pressures are good and adequately reflect changes in configuration.

Tri-fuel (diesel-biodiesel-ethanol) emulsion characterization, stability and the corrosion effect

NASA Astrophysics Data System (ADS)

Low, M. H.; Mukhtar, N. A. M.; Yohaness Hagos, Ftwi; Noor, M. M.

2017-10-01

This paper presents the result of experimenting emulsified tri-fuel in term of stability, physico-chemical properties and corrosion effect on three common metals. The results were interpreted in terms of the impact of five minutes emulsification approach. Tri-fuel emulsions were varied in proportion ratio consist of biodiesel; 0%, 5%, 10%, and ethanol; 5%, 10%, 15%. Fuel characterization includes density, calorific value, flash point, and kinematic viscosity. Flash point of tri-fuel emulsion came with range catalog. Calorific value of tri-fuel emulsion appeared in declining pattern as more ethanol and biodiesel were added. Biodiesel promoted flow resistance while ethanol with opposite effect. 15% ethanol content in tri-fuel emulsion separated faster than 10% ethanol content but ethanol content with 5% yield no phase separation at all. Close cap under static immersion with various ratio of tri-fuel emulsions for over a month, corrosiveness attack was detected via weight loss technique on aluminum, stainless steel and mild steel.

Preparation of O/I1-type Emulsions and S/I1-type Dispersions Encapsulating UV-Absorbing Agents.

PubMed

Aramaki, Kenji; Kimura, Minami; Masuda, Kazuki

2015-01-01

Oil-in-cubic phase (O/I1) emulsions encapsulating the cosmetic UV absorbing agents 2-ethylhexyl 4-methoxycinnamate (EHMC), 2-ethylhexyl 2-cyano-3,3-diphenylacrylate (octocrylene, OCR) and 1-(4-tertbutylphenyl)-3-(4-methoxyphenyl)-1,3-propanedione (Avobenzone, TBMP) were prepared by vortex mixing accompanied by a heating-cooling process. A ternary phase diagram in a water/C12EO25/EHMC system at 25°C was constructed and the two-phase equilibrium of an oil phase and an I1 phase, which is necessary to prepare the O/I1-type emulsions, was confirmed. Also, the melting of the I1 phase into a fluid micellar solution phase was confirmed, allowing emulsification by a heating-cooling process. The O/I1-type emulsions were formulated in the ternary system as well as a quaternary system. The four-component system contained an additional cosolvent, isopropyl myristate (IPM). The use of the cosolvent allows the use of reduced amounts of EHMC, which is desirable because EHMC can cause temporary skin irritation. Formulation of the O/I1-type emulsions with other UV absorbing agents (OCR and TBMP) was also possible using the same emulsification method. When IPM was changed to tripalmitin, which has a melting point greater than room temperature, a solid-oil dispersion in I1 phase was formed. We have termed this a "solidin-cubic phase (S/I1) type dispersion". These novel emulsions have not been reported previously. The UV absorbability of the O/I1-type emulsions and S/I1-type dispersions that encapsulate the UV absorbing agents was confirmed by measurement of UV absorption spectra.

FOULING-RESISTANT CERAMIC MEMBRANES FOR TREATMENT OF METASTABLE OIL/WATER EMULSIONS - PHASE II

EPA Science Inventory

Billions of gallons of oily wastewaters are generated daily by a variety of industrial sources. A large fraction of these are oil/water emulsions for which current treatment technologies are often costly and ineffective. Although such emulsions can be separated using crossf...

Experimental parametric study of jet vortex generators for flow separation control

NASA Technical Reports Server (NTRS)

Selby, Gregory

1991-01-01

A parametric wind-tunnel study was performed with jet vortex generators to determine their effectiveness in controlling flow separation associated with low-speed turbulence flow over a two-dimensional rearward-facing ramp. Results indicate that flow-separation control can be accomplished, with the level of control achieved being a function of jet speed, jet orientation (with respect to the free-stream direction), and orifice pattern (double row of jets vs. single row). Compared to slot blowing, jet vortex generators can provide an equivalent level of flow control over a larger spanwise region (for constant jet flow area and speed). Dye flow visualization tests in a water tunnel indicated that the most effective jet vortex generator configurations produced streamwise co-rotating vortices.

VORSTAB: A computer program for calculating lateral-directional stability derivatives with vortex flow effect

NASA Technical Reports Server (NTRS)

Lan, C. Edward

1985-01-01

A computer program based on the Quasi-Vortex-Lattice Method of Lan is presented for calculating longitudinal and lateral-directional aerodynamic characteristics of nonplanar wing-body combination. The method is based on the assumption of inviscid subsonic flow. Both attached and vortex-separated flows are treated. For the vortex-separated flow, the calculation is based on the method of suction analogy. The effect of vortex breakdown is accounted for by an empirical method. A summary of the theoretical method, program capabilities, input format, output variables and program job control set-up are described. Three test cases are presented as guides for potential users of the code.

Application of petroleum demulsification technology to shale oil emulsions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robertson, R.E.

1983-01-01

Demulsification, the process of emulsion separation, of water-in-oil shale oil emulsions produced by several methods was accomplished using commercial chemical demulsifiers which are used typically for petroleum demulsification. The shale oil emulsions were produced from Green River shale by one in situ and three different above-ground retorts, an in situ high pressure/high temperature steam process, and by washing both retort-produced and hydrotreated shale oils.

Point vortex modelling of the wake dynamics behind asymmetric vortex generator arrays

NASA Astrophysics Data System (ADS)

Baldacchino, D.; Ferreira, C.; Ragni, D.; van Bussel, G. J. W.

2016-09-01

In this work, we present a simple inviscid point vortex model to study the dynamics of asymmetric vortex rows, as might appear behind misaligned vortex generator vanes. Starting from the existing solution of the infinite vortex cascade, a numerical model of four base-vortices is chosen to represent two primary counter-rotating vortex pairs and their mirror plane images, introducing the vortex strength ratio as a free parameter. The resulting system of equations is also defined in terms of the vortex row separation and the qualitative features of the ensuing motion are mapped. A translating and orbiting regime are identified for different cascade separations. The latter occurs for all unequal strength vortex pairs. Thus, the motion is further classified by studying the cyclic behaviour of the orbiting regime and it is shown that for small mismatches in vortex strength, the orbiting length and time scales are sufficiently large as to appear, in the near wake, as translational (non-orbiting). However, for larger mismatches in vortex strength, the orbiting motion approaches the order of the starting height of the vortex. Comparisons between experimental data and the potential flow model show qualitative agreement whilst viscous effects account for the major discrepancies. Despite this, the model captures the orbital mode observed in the measurements and provides an impetus for considering the impact of these complex interactions on vortex generator designs.

Cellulose acetate-based SiO2/TiO2 hybrid microsphere composite aerogel films for water-in-oil emulsion separation

NASA Astrophysics Data System (ADS)

Yang, Xue; Ma, Jianjun; Ling, Jing; Li, Na; Wang, Di; Yue, Fan; Xu, Shimei

2018-03-01

The cellulose acetate (CA)/SiO2-TiO2 hybrid microsphere composite aerogel films were successfully fabricated via water vapor-induced phase inversion of CA solution and simultaneous hydrolysis/condensation of 3-aminopropyltrimethoxysilane (APTMS) and tetrabutyl titanate (TBT) at room temperature. Micro-nano hierarchical structure was constructed on the surface of the film. The film could separate nano-sized surfactant-stabilized water-in-oil emulsions only under gravity. The flux of the film for the emulsion separation was up to 667 L m-2 h-1, while the separation efficiency was up to 99.99 wt%. Meanwhile, the film exhibited excellent stability during multiple cycles. Moreover, the film performed excellent photo-degradation performance under UV light due to the photocatalytic ability of TiO2. Facile preparation, good separation and potential biodegradation maked the CA/SiO2-TiO2 hybrid microsphere composite aerogel films a candidate in oil/water separation application.

Demulsification of oil-in-water emulsions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roark, D.N.

1986-09-30

This patent describes a process of demulsifying an oil-in-water emulsion which comprises admixing with the emulsion a water-soluble polymer of monoallylamine that causes formation of and separation between an oil phase and an aqueous phase to occur. The emulsion has a pH in the range of about 5 to about 10 and the polymer has a weight average molecular weight of at least 1000 and contains at least 95% by weight of monoallylamine.

Interactions of a co-rotating vortex pair at multiple offsets

NASA Astrophysics Data System (ADS)

Forster, Kyle J.; Barber, Tracie J.; Diasinos, Sammy; Doig, Graham

2017-05-01

Two NACA0012 vanes at various lateral offsets were investigated by wind tunnel testing to observe the interactions between the streamwise vortices. The vanes were separated by nine chord lengths in the streamwise direction to allow the upstream vortex to impact on the downstream geometry. These vanes were evaluated at an angle of incidence of 8° and a Reynolds number of 7 ×104 using particle image velocimetry. A helical motion of the vortices was observed, with rotational rate increasing as the offset was reduced to the point of vortex merging. Downstream meandering of the weaker vortex was found to increase in magnitude near the point of vortex merging. The merging process occurred more rapidly when the upstream vortex was passed on the pressure side of the vane, with the downstream vortex being produced with less circulation and consequently merging into the upstream vortex. The merging distance was found to be statistical rather than deterministic quantity, indicating that the meandering of the vortices affected their separations and energies. This resulted in a fluctuation of the merging location. A loss of circulation associated with the merging process was identified, with the process of achieving vortex circularity causing vorticity diffusion, however all merged cases maintained higher circulation than a single vortex condition. The presence of the upstream vortex was found to reduce the strength of the downstream vortex in all offsets evaluated.

Simple preparation of magnetic field-responsive structural colored Janus particles.

PubMed

Teshima, Midori; Seki, Takahiro; Takeoka, Yukikazu

2018-03-08

We established a simple method for preparing Janus particles displaying different structural colors using submicron-sized fine silica particles and magnetic nanoparticles composed of Fe 3 O 4 . A w/o emulsion is prepared by vortex-stirring a mixed aqueous solution of suspended fine silica particles and magnetic nanoparticles and of hexadecane containing an emulsifier. Subsequent drying of the emulsion on a hot plate using a magnetic stirrer provides a polydisperse particle aggregate displaying two different structural colors according to the ratio of the amount of fine silica particles to the amount of magnetic nanoparticles. This polydisperse particle aggregate can be converted into monodisperse particles simply by using a sieve made of stainless steel. In the presence of a magnet, the monodisperse Janus particles can change their orientation and can switch between two different structural colors.

S-Duct Engine Inlet Flow Control Using SDBD Plasma Streamwise Vortex Generators

NASA Astrophysics Data System (ADS)

Kelley, Christopher; He, Chuan; Corke, Thomas

2009-11-01

The results of a numerical simulation and experiment characterizing the performance of plasma streamwise vortex generators in controlling separation and secondary flow within a serpentine, diffusing duct are presented. A no flow control case is first run to check agreement of location of separation, development of secondary flow, and total pressure recovery between the experiment and numerical results. Upon validation, passive vane-type vortex generators and plasma streamwise vortex generators are implemented to increase total pressure recovery and reduce flow distortion at the aerodynamic interface plane: the exit of the S-duct. Total pressure recovery is found experimentally with a pitot probe rake assembly at the aerodynamic interface plane. Stagnation pressure distortion descriptors are also presented to show the performance increase with plasma streamwise vortex generators in comparison to the baseline no flow control case. These performance parameters show that streamwise plasma vortex generators are an effective alternative to vane-type vortex generators in total pressure recovery and total pressure distortion reduction in S-duct inlets.

A vortex-filament and core model for wings with edge vortex separation

NASA Technical Reports Server (NTRS)

Pao, J. L.; Lan, C. E.

1981-01-01

A method for predicting aerodynamic characteristics of slender wings with edge vortex separation was developed. Semiempirical but simple methods were used to determine the initial positions of the free sheet and vortex core. Comparison with available data indicates that: the present method is generally accurate in predicting the lift and induced drag coefficients but the predicted pitching moment is too positive; the spanwise lifting pressure distributions estimated by the one vortex core solution of the present method are significantly better than the results of Mehrotra's method relative to the pressure peak values for the flat delta; the two vortex core system applied to the double delta and strake wing produce overall aerodynamic characteristics which have good agreement with data except for the pitching moment; and the computer time for the present method is about two thirds of that of Mehrotra's method.

Visualization of flow separation and control by vortex generators on an single flap in landing configuration

NASA Astrophysics Data System (ADS)

Součková, Natálie; Kuklová, Jana; Popelka, Lukáš; Matějka, Milan

2012-04-01

This paper focuses on a suppression of the flow separation, which occurs on a deflected flap, by means of vortex generators (VG's). An airfoil NACA 63A421 with a simple flap and vane-type vortex generators were used. The investigation was carried out by using experimental and numerical methods. The data from the numerical simulation of the flapped airfoil without VG's control were used for the vortex generator design. Two sizes, two different shapes and various spacing of the vortex generators were tested. The flow past the airfoil was visualized through three methods, namely tuft filaments technique, oil and thermo camera visualization. The experiments were performed in closed circuit wind tunnels with closed and open test sections. The lift curves for both cases without and with vortex generators were acquired for a lift coefficient improvement determination. The improvement was achieved for several cases by means all of the applied methods.

Wind-tunnel studies of advanced cargo aircraft concepts. [leading edge vortex flaps for drag reduction

NASA Technical Reports Server (NTRS)

Rao, D. M.; Goglia, G. L.

1981-01-01

Accomplishments in vortex flap research are summarized. A singular feature of the vortex flap is that, throughout the range of angle of attack range, the flow type remains qualitatively unchanged. Accordingly, no large or sudden change in the aerodynamic characteristics, as happens when forcibly maintained attached flow suddenly reverts to separation, will occur with the vortex flap. Typical wind tunnel test data are presented which show the drag reduction potential of the vortex flap concept applied to a supersonic cruise airplane configuration. The new technology offers a means of aerodynamically augmenting roll-control effectiveness on slender wings at higher angles of attack by manipulating the vortex flow generated from leading edge separation. The proposed manipulator takes the form of a flap hinged at or close to the leading edge, normally retracted flush with the wing upper surface to conform to the airfoil shape.

Preliminary study of the three-dimensional deformation of the vortex in Karman vortex street

NASA Astrophysics Data System (ADS)

Ling, Guocan; Guo, Liang; Wu, Zuobin; Ma, Huiyang

1992-03-01

The mechanism for 3D evolution of the isolated Karman vortex and the thin-vortex filament in a circular cylinder wake is studied numerically using the LIA method. The results show that the vortex motion is unstable for small 3D disturbances in the separated wake of a circular cylinder. Karman vortex in the time-averaged wake flowfield wolves into a horseshoe-spoon-like 3D structure. The thin vortex filament deforms three-dimensionally in the braid and generates streamwise vortex structures which incline to the region maximum-deformation direction of the flowfield.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, M., E-mail: chengm@ihpc.a-star.edu.sg; Lou, J.; Lim, T. T.

A recent theoretical study [Borisov, Kilin, and Mamaev, “The dynamics of vortex rings: Leapfrogging, choreographies and the stability problem,” Regular Chaotic Dyn. 18, 33 (2013); Borisov et al., “The dynamics of vortex rings: Leapfrogging in an ideal and viscous fluid,” Fluid Dyn. Res. 46, 031415 (2014)] shows that when three coaxial vortex rings travel in the same direction in an incompressible ideal fluid, each of the vortex rings alternately slips through (or leapfrogs) the other two ahead. Here, we use a lattice Boltzmann method to simulate viscous vortex rings with an identical initial circulation, radius, and separation distance with themore » aim of studying how viscous effect influences the outcomes of the leapfrogging process. For the case of two identical vortex rings, our computation shows that leapfrogging can be achieved only under certain favorable conditions, which depend on Reynolds number, vortex core size, and initial separation distance between the two rings. For the case of three coaxial vortex rings, the result differs from the inviscid model and shows that the second vortex ring always slips through the leading ring first, followed by the third ring slipping through the other two ahead. A simple physical model is proposed to explain the observed behavior.« less

Characteristics of wake vortex generated by a Boeing 727 jet transport during two-segment and normal ILS approach flight paths

NASA Technical Reports Server (NTRS)

Kurkowski, R. L.; Barber, M. R.; Garodz, L. J.

1976-01-01

A series of flight tests was conducted to evaluate the vortex wake characteristics of a Boeing 727 (B727-200) aircraft during conventional and two-segment ILS approaches. Twelve flights of the B727, which was equipped with smoke generators for vortex marking, were flown and its vortex wake was intentionally encountered by a Lear Jet model 23 (LR-23) and a Piper Twin Comanche (PA-30). Location of the B727 vortex during landing approach was measured using a system of photo-theodolites. The tests showed that at a given separation distance there were no readily apparent differences in the upsets resulting from deliberate vortex encounters during the two types of approaches. Timed mappings of the position of the landing configuration vortices showed that they tended to descend approximately 91 m(300 ft) below the flight path of the B727. The flaps of the B727 have a dominant effect on the character of the trailed wake vortex. The clean wing produces a strong, concentrated vortex but as the flaps are lowered, the vortex system becomes more diffuse. Pilot opinion and roll acceleration data indicate that 4.5 n.mi. would be a minimum separation distance at which roll control of light aircraft (less than 5,670 kg (12,500 lb) could be maintained during parallel encounters of the B727's landing configuration wake. This minimum separation distance is generally in scale with results determined from previous tests of other aircraft using the small roll control criteria.

Wake-Vortex Separation Distances when Flight-Path Corridors are Constrained

NASA Technical Reports Server (NTRS)

Rossow, Vernon J.; Olson, Lawrence E. (Technical Monitor)

1995-01-01

Since the vortex wakes of large transport aircraft can pose a hazard to smaller following aircraft during landing and takeoff operations, certain separation guidelines are followed while aircraft are in the approach and departure corridors at airports. These guidelines reduce the capacity of airports because the separation distances are larger than other airport factors require. This paper studies the effect that a decrease in the size of the cross-section of the flight corridors for air traffic control would have on the wake-vortex separation guidelines; e.g., when the Global Positioning System (GPS) is implemented for air traffic control. It is first shown why smaller flight corridors permit reduced spacings at airports. Several arrangements of smaller flight corridors are then presented to illustrate how differing atmospheric and airport conditions can be accommodated. These considerations indicate that a reduction is then permissible in the wake-vortex spacings while still retaining the same or an improved degree of safety.

Vortex developments over steady and accelerated airfoils incorporating a trailing edge jet

NASA Technical Reports Server (NTRS)

Finaish, F.; Okong'o, N.; Frigerio, J.

1993-01-01

Computational and experimental studies are conducted to investigate the influence of a trailing edge jet on flow separation and subsequent vortex formation over steady and accelerated airfoils at high angles of attack. A computer code, employing the stream function-vorticity approach, is developed and utilized to conduct numerical experiments on the flow problem. To verify and economize such efforts, an experimental system is developed and incorporated into a subsonic wind tunnel where streamline and vortex flow visualization experiments are conducted. The study demonstrates the role of the trailing edge jet in controlling flow separation and subsequent vortex development for steady and accelerating flow at angles past the static stall angle of attack. The results suggest that the concept of the trailing edge jet may be utilized to control the characteristics of unsteady separated flows over lifting surfaces. This control possibility seems to be quite effective and could have a significant role in controlling unsteady separated flows.

A point vortex model for the formation of ocean eddies by flow separation

NASA Astrophysics Data System (ADS)

Southwick, O. R.; Johnson, E. R.; McDonald, N. R.

2015-01-01

A simple model for the formation of ocean eddies by flow separation from sharply curved horizontal boundary topography is developed. This is based on the Brown-Michael model for two-dimensional vortex shedding, which is adapted to more realistically model mesoscale oceanic flow by including a deforming free surface. With a free surface, the streamfunction for the flow is not harmonic so the conformal mapping methods used in the standard Brown-Michael approach cannot be used and the problem must be solved numerically. A numerical scheme is developed based on a Chebyshev spectral method for the streamfunction partial differential equation and a second order implicit timestepping scheme for the vortex position ordinary differntial equations. This method is used to compute shed vortex trajectories for three background flows: (A) a steady flow around a semi-infinite plate, (B) a free vortex moving around a semi-infinite plate, and (C) a free vortex moving around a right-angled wedge. In (A), the inclusion of surface deformation dramatically slows the vortex and changes its trajectory from a straight path to a curved one. In (B) and (C), without the inclusion of flow separation, free vortices traverse fully around the tip along symmetrical trajectories. With the effects of flow separation included, very different trajectories are found: for all values of the model parameter—the Rossby radius—the free and shed vortices pair up and move off to infinity without passing around the tip. Their final propagation angle depends strongly and monotonically on the Rossby radius.

Process for removing sulfate anions from waste water

DOEpatents

Nilsen, David N.; Galvan, Gloria J.; Hundley, Gary L.; Wright, John B.

1997-01-01

A liquid emulsion membrane process for removing sulfate anions from waste water is disclosed. The liquid emulsion membrane process includes the steps of: (a) providing a liquid emulsion formed from an aqueous strip solution and an organic phase that contains an extractant capable of removing sulfate anions from waste water; (b) dispersing the liquid emulsion in globule form into a quantity of waste water containing sulfate anions to allow the organic phase in each globule of the emulsion to extract and absorb sulfate anions from the waste water and (c) separating the emulsion including its organic phase and absorbed sulfate anions from the waste water to provide waste water containing substantially no sulfate anions.

Coherent Pulsed Lidar Sensing of Wake Vortex Position and Strength, Winds and Turbulence in the Terminal Area

NASA Technical Reports Server (NTRS)

Brockman, Philip; Barker, Ben C., Jr.; Koch, Grady J.; Nguyen, Dung Phu Chi; Britt, Charles L., Jr.; Petros, Mulugeta

1999-01-01

NASA Langley Research Center (LaRC) has field tested a 2.0 gm, 100 Hertz, pulsed coherent lidar to detect and characterize wake vortices and to measure atmospheric winds and turbulence. The quantification of aircraft wake-vortex hazards is being addressed by the Wake Vortex Lidar (WVL) Project as part of Aircraft Vortex Spacing System (AVOSS), which is under the Reduced Spacing Operations Element of the Terminal Area Productivity (TAP) Program. These hazards currently set the minimum, fixed separation distance between two aircraft and affect the number of takeoff and landing operations on a single runway under Instrument Meteorological Conditions (IMC). The AVOSS concept seeks to safely reduce aircraft separation distances, when weather conditions permit, to increase the operational capacity of major airports. The current NASA wake-vortex research efforts focus on developing and validating wake vortex encounter models, wake decay and advection models, and wake sensing technologies. These technologies will be incorporated into an automated AVOSS that can properly select safe separation distances for different weather conditions, based on the aircraft pair and predicted/measured vortex behavior. The sensor subsystem efforts focus on developing and validating wake sensing technologies. The lidar system has been field-tested to provide real-time wake vortex trajectory and strength data to AVOSS for wake prediction verification. Wake vortices, atmospheric winds, and turbulence products have been generated from processing the lidar data collected during deployments to Norfolk (ORF), John F. Kennedy (JFK), and Dallas/Fort Worth (DFW) International Airports.

One-step production of multiple emulsions: microfluidic, polymer-stabilized and particle-stabilized approaches.

PubMed

Clegg, Paul S; Tavacoli, Joe W; Wilde, Pete J

2016-01-28

Multiple emulsions have great potential for application in food science as a means to reduce fat content or for controlled encapsulation and release of actives. However, neither production nor stability is straightforward. Typically, multiple emulsions are prepared via two emulsification steps and a variety of approaches have been deployed to give long-term stability. It is well known that multiple emulsions can be prepared in a single step by harnessing emulsion inversion, although the resulting emulsions are usually short lived. Recently, several contrasting methods have been demonstrated which give rise to stable multiple emulsions via one-step production processes. Here we review the current state of microfluidic, polymer-stabilized and particle-stabilized approaches; these rely on phase separation, the role of electrolyte and the trapping of solvent with particles respectively.

Qualitative numerical study of simultaneous high-G-intensified gas–solids contact, separation and segregation in a bi-disperse rotating fluidized bed in a vortex chamber

DOE PAGES

De Wilde, Juray; Richards, George; Benyahia, Sofiane

2016-05-13

Coupled discrete particle method – computational fluid dynamics simulations are carried out to demonstrate the potential of combined high-G-intensified gas-solids contact, gas-solids separation and segregation in a rotating fluidized bed in a static vortex chamber. A case study with two distinct types of particles is focused on. When feeding solids using a standard solids inlet design, a dense and uniform rotating fluidized bed is formed, guaranteeing intense gas-solids contact. The presence of both types of particles near the chimney region reduces, however, the strength of the central vortex and is detrimental for separation and segregation. Optimization of the solids inletmore » design is required, as illustrated by stopping the solids feeding. High-G separation and segregation of the batch of particles is demonstrated, as the strength of the central vortex is restored. The flexibility with respect to the gas flow rate of the bed density and uniformity and of the gas-solids separation and segregation is demonstrated, a unique feature of vortex chamber generated rotating fluidized beds. With the particles considered in this case study, turbulent dispersion by large eddies in the gas phase is shown to have only a minor impact on the height of the inner bed of small/light particles.« less

Review of Research on Low-Profile Vortex Generators to Control Boundary-Layer Separation

NASA Technical Reports Server (NTRS)

Lin, John C.

2002-01-01

An in-depth review of boundary-layer flow-separation control by a passive method using low-profile vortex generators is presented. The generators are defined as those with a device height between 10% and 50% of the boundary layer thickness. Key results are presented for several research efforts, all of which were performed within the past decade and a half where the majority of these works emphasize experimentation with some recent efforts on numerical simulations. Topics of discussion consist of both basic fluid dynamics and applied aerodynamics research. The fluid dynamics research includes comparative studies on separation control effectiveness as well as device-induced vortex characterization and correlation. The comparative studies cover the controlling of low-speed separated flows in adverse pressure gradient and supersonic shock-induced separation. The aerodynamics research includes several applications for aircraft performance enhancement and covers a wide range of speeds. Significant performance improvements are achieved through increased lift and/or reduced drag for various airfoils-low-Reynolds number, high-lift, and transonic-as well as highly swept wings. Performance enhancements for non-airfoil applications include aircraft interior noise reduction, inlet flow distortion alleviation inside compact ducts, and a more efficient overwing fairing. The low-profile vortex generators are best for being applied to applications where flow-separation locations are relatively fixed and the generators can be placed reasonably close upstream of the separation. Using the approach of minimal near-wall proturbances through substantially reduced device height, these devices can produce streamwise vortices just strong enough to overcome the separation without unnecessarily persisting within the boundary layer once the flow-control objective is achieved. Practical advantages of low-profile vortex generators, such as their inherent simplicity and low device drag, are demonstrated to be critically important for many applications as well.

Long-term stability of crystal-stabilized water-in-oil emulsions.

PubMed

Ghosh, Supratim; Pradhan, Mamata; Patel, Tejas; Haj-Shafiei, Samira; Rousseau, Dérick

2015-12-15

The impact of cooling rate and mixing on the long-term kinetic stability of wax-stabilized water-in-oil emulsions was investigated. Four cooling/mixing protocols were investigated: cooling from 45°C to either 25°C or 4°C with/without stirring and two cooling rates - slow (1°C/min) and fast (5°C/min). The sedimentation behaviour of the emulsions was significantly affected by cooling protocol. Stirring was critical to the stability of all emulsions, with statically-cooled (no stirring) emulsions suffering from extensive aqueous phase separation. Emulsions stirred while cooling showed sedimentation of a waxy emulsion layer leaving a clear oil layer at the top, with a smaller separation and droplet size distribution at 4°C compared to 25°C, indicating the importance of the amount of crystallized wax on emulsion stability. Light microscopy revealed that crystallized wax appeared both on the droplet surface and in the continuous phase, suggesting that stirring ensured dispersibility of the water droplets during cooling as the wax was crystallizing. Wax crystallization on the droplet surface provided stability against droplet coalescence while continuous phase wax crystals minimized inter-droplet collisions. The key novel aspect of this research is in the simplicity to tailor the spatial distribution of wax crystals, i.e., either at the droplet surface or in the continuous phase via use of a surfactant and judicious stirring and/or cooling. Knowledge gained from this research can be applied to develop strategies for long-term storage stability of crystal-stabilized W/O emulsions. Copyright © 2015 Elsevier Inc. All rights reserved.

Emulsified industrial oils recycling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gabris, T.

1982-04-01

The industrial lubricant market has been analyzed with emphasis on current and/or developing recycling and re-refining technologies. This task has been performed for the United States and other industrialized countries, specifically France, West Germany, Italy and Japan. Attention has been focused at emulsion-type fluids regardless of the industrial application involved. It was found that emulsion-type fluids in the United States represent a much higher percentage of the total fluids used than in other industrialized countries. While recycling is an active matter explored by the industry, re-refining is rather a result of other issues than the mere fact that oil canmore » be regenerated from a used industrial emulsion. To extend the longevity of an emulsion is a logical step to keep expenses down by using the emulsion as long as possible. There is, however, another important factor influencing this issue: regulations governing the disposal of such fluids. The ecological question, the respect for nature and the natural balances, is often seen now as everybody's task. Regulations forbid dumping used emulsions in the environment without prior treatment of the water phase and separation of the oil phase. This is a costly procedure, so recycling is attractive since it postpones the problem. It is questionable whether re-refining of these emulsions - as a business - could stand on its own if these emulsions did not have to be taken apart for disposal purposes. Once the emulsion is separated into a water and an oil phase, however, re-refining of the oil does become economical.« less

Lift enhancement by trapped vortex

NASA Technical Reports Server (NTRS)

Rossow, Vernon J.

1992-01-01

The viewgraphs and discussion of lift enhancement by trapped vortex are provided. Efforts are continuously being made to find simple ways to convert wings of aircraft from an efficient cruise configuration to one that develops the high lift needed during landing and takeoff. The high-lift configurations studied here consist of conventional airfoils with a trapped vortex over the upper surface. The vortex is trapped by one or two vertical fences that serve as barriers to the oncoming stream and as reflection planes for the vortex and the sink that form a separation bubble on top of the airfoil. Since the full three-dimensional unsteady flow problem over the wing of an aircraft is so complicated that it is hard to get an understanding of the principles that govern the vortex trapping process, the analysis is restricted here to the flow field illustrated in the first slide. It is assumed that the flow field between the two end plates approximates a streamwise strip of the flow over a wing. The flow between the endplates and about the airfoil consists of a spanwise vortex located between the suction orifices in the endplates. The spanwise fence or spoiler located near the nose of the airfoil serves to form a separated flow region and a shear layer. The vorticity in the shear layer is concentrated into the vortex by withdrawal of fluid at the suction orifices. As the strength of the vortex increases with time, it eventually dominates the flow in the separated region so that a shear or vertical layer is no longer shed from the tip of the fence. At that point, the vortex strength is fixed and its location is such that all of the velocity contributions at its center sum to zero thereby making it an equilibrium point for the vortex. The results of a theoretical analysis of such an idealized flow field are described.

Estimates of the initial vortex separation distance, bo, of commercial aircraft from pulsed lidar data

DOT National Transportation Integrated Search

2013-01-07

An aircraft in flight generates multiple wake vortices, the largest of which are a result of : the lift on the wings. These vortices rapidly roll up into a counter-rotating vortex pair : behind the aircraft. The initial separation between the centroi...

Control of Flap Vortices

NASA Technical Reports Server (NTRS)

Greenblatt, David

2005-01-01

A wind tunnel investigation was carried out on a semi-span wing model to assess the feasibility of controlling vortices emanating from outboard flaps and tip-flaps by actively varying the degree of boundary layer separation. Separation was varied by means of perturbations produced from segmented zero-efflux oscillatory blowing slots, while estimates of span loadings and vortex sheet strengths were obtained by integrating wing surface pressures. These estimates were used as input to inviscid rollup relations as a means of predicting changes to the vortex characteristics resulting from the perturbations. Surveys of flow in the wake of the outboard and tip-flaps were made using a seven-hole probe, from which the vortex characteristics were directly deduced. Varying the degree of separation had a marked effect on vortex location, strength, tangential velocity, axial velocity and size for both outboard and tip-flaps. Qualitative changes in vortex characteristics were well predicted by the inviscid rollup relations, while the failure to account for viscosity was presumed to be the main reason for observed discrepancies. Introducing perturbations near the outboard flap-edges or on the tip-flap exerted significant control over vortices while producing negligible lift excursions.

Further theoretical studies of modified cyclone separator as a diesel soot particulate emission arrester.

PubMed

Mukhopadhyay, N; Bose, P K

2009-10-01

Soot particulate emission reduction from diesel engine is one of the most emerging problems associated with the exhaust pollution. Diesel particulate filters (DPF) hold out the prospects of substantially reducing regulated particulate emissions but the question of the reliable regeneration of filters still remains a difficult hurdle to overcome. Many of the solutions proposed to date suffer from design complexity, cost, regeneration problem and energy demands. This study presents a computer aided theoretical analysis for controlling diesel soot particulate emission by cyclone separator--a non contact type particulate removal system considering outer vortex flow, inner vortex flow and packed ceramic fiber filter at the end of vortex finder tube. Cyclone separator with low initial cost, simple construction produces low back pressure and reasonably high collection efficiencies with reduced regeneration problems. Cyclone separator is modified by placing a continuous ceramic packed fiber filter placed at the end of the vortex finder tube. In this work, the grade efficiency model of diesel soot particulate emission is proposed considering outer vortex, inner vortex and the continuous ceramic packed fiber filter. Pressure drop model is also proposed considering the effect of the ceramic fiber filter. Proposed model gives reasonably good collection efficiency with permissible pressure drop limit of diesel engine operation. Theoretical approach is predicted for calculating the cut size diameter considering the effect of Cunningham molecular slip correction factor. The result shows good agreements with existing cyclone and DPF flow characteristics.

Lentil and chickpea protein-stabilized emulsions: optimization of emulsion formulation.

PubMed

Can Karaca, Asli; Nickerson, Michael T; Low, Nicholas H

2011-12-28

Chickpea and lentil protein-stabilized emulsions were optimized with regard to pH (3.0-8.0), protein concentration (1.1-4.1% w/w), and oil content (20-40%) for their ability to form and stabilize oil-in-water emulsions using response surface methodology. Specifically, creaming stability, droplet size, and droplet charge were assessed. Optimum conditions for minimal creaming (no serum separation after 24 h), small droplet size (<2 μm), and high net droplet charge (absolute value of ZP > 40 mV) were identified as 4.1% protein, 40% oil, and pH 3.0 or 8.0, regardless of the plant protein used for emulsion preparation.

Vortex Formation During Unsteady Boundary-Layer Separation

NASA Astrophysics Data System (ADS)

Das, Debopam; Arakeri, Jaywant H.

1998-11-01

Unsteady laminar boundary-layer separation is invariably accompanied by the formation of vortices. The aim of the present work is to study the vortex formation mechanism(s). An adverse pressure gradient causing a separation can be decomposed into a spatial component ( spatial variation of the velocity external to the boundary layer ) and a temporal component ( temporal variation of the external velocity ). Experiments were conducted in a piston driven 2-D water channel, where the spatial component could be be contolled by geometry and the temporal component by the piston motion. We present results for three divergent channel geometries. The piston motion consists of three phases: constant acceleration from start, contant velocity, and constant deceleration to stop. Depending on the geometry and piston motion we observe different types of unsteady separation and vortex formation.

Comparison and validation of wake vortex characteristics collected at different airports by different scanning lidar sensors

NASA Astrophysics Data System (ADS)

Thobois, Ludovic; Cariou, Jean-Pierre; Cappellazzo, Valerio; Musson, Christian; Treve, Vincent

2018-04-01

Today, the demand for increasing airport capacity is high, in particular for increasing runway throughput from an ATM perspective. Runway capacity is often directly linked with the minima longitudinal separation between aircraft on approach phase or between aircraft on departure. The separation minima are based on surveillance capabilities and on wake turbulence (WT) in order to mitigate respectively collision risk and WT-induced accidents, therefore WT hazard becomes a major concern for ATM. For ten years, many research LIDAR systems have been used for better understanding wake vortices behaviors in the operational environment within large range of wind and turbulence conditions. All these studies[1][2] helped to design new concepts of wake separations between aircrafts thanks to the proven capabilities of LIDAR systems to assess the risks of wake vortex (WV) encounters through the circulation retrievals. The re-categorization project, called RECAT [8], has been launched by a joint EUROCONTROL - FAA initiative in order to renew and optimize the out-of-date currently applied ICAO regulations on distance separation. Nowadays, the first phase of regional RECAT projects, which consists in defining new distance separation matrices composed of six/seven static aircraft categories instead of three, entered the operational phase and is deployed in several airports in United States and Europe. In addition, other concepts like Time-Based Separation have also been studied and deployed in London Heathrow. The airports where these solutions have been deployed obtained significant benefits as increased runway throughput and improved resilience to disruptions. For implementing such new WT solutions at an airport, a local safety assessment before the implementation and a risk monitoring after are usually needed. Before implementation, it may be required to determine for the targeted airport the relative variations of risk of wake vortex encounters, given the local ATM rules, the traffic mix, the weather conditions and their impact on the wake vortex decay. After implementation, the risk monitoring might perform in-depth analysis of wake vortex encounter reported by pilots. For all the mentioned steps, the use of scanning Doppler LIDARs is the only experimental sensor capable of measuring the localization and the circulation of the wake vortices and to provide ground truth wake vortex measurements. Next generation operational LIDARs need to be developed to address in a cost effective way these operational needs. Furthermore, a specific configuration and methodology need to be developed to ensure the accuracy of the wake vortex data. Such a LIDAR based wake vortex solution has been tested at Paris Charles De Gaulle which implemented the RECAT-EU wake separation scheme. The wake vortex circulation, initial spacing and decay measured have been compared to the data collected in London Heathrow by a different LIDAR sensor. The results indicated that the initial circulation, the time to demise, the decay curve evolution and the vortex spacing are very coherent between the two databases.

Numerical Analysis of Incipient Separation on 53 Deg Swept Diamond Wing

NASA Technical Reports Server (NTRS)

Frink, Neal T.

2015-01-01

A systematic analysis of incipient separation and subsequent vortex formation from moderately swept blunt leading edges is presented for a 53 deg swept diamond wing. This work contributes to a collective body of knowledge generated within the NATO/STO AVT-183 Task Group titled 'Reliable Prediction of Separated Flow Onset and Progression for Air and Sea Vehicles'. The objective is to extract insights from the experimentally measured and numerically computed flow fields that might enable turbulence experts to further improve their models for predicting swept blunt leading-edge flow separation. Details of vortex formation are inferred from numerical solutions after establishing a good correlation of the global flow field and surface pressure distributions between wind tunnel measurements and computed flow solutions. From this, significant and sometimes surprising insights into the nature of incipient separation and part-span vortex formation are derived from the wealth of information available in the computational solutions.

Demulsification of water/oil/solid emulsions by hollow-fiber membranes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tirmizi, N.P.; Raghuraman, B.; Wiencek, J.

1996-05-01

The demulsification techniques investigated use preferential surface wetting to allow separation of oil and water phases in ultrafiltration and microfiltration membranes. A hydrophobic membrane allows the permeation of an oil phase at almost zero pressure and retains the water phase, even though the molecular weight of the water molecule (18) is much smaller than that of the oil molecule (198 for tetradecane, used in this study). Hydrophobic membranes having pore sizes from 0.02 to 0.2 {micro}m were tested for demulsification of water-in-oil emulsions and water/oil/solid mixtures. The dispersed (aqueous)-phase drop sizes ranged from 1 to 5 {micro}m. High separation rates,more » as well as good permeate quality, were obtained with microfiltration membranes. Water content of permeating oil was 32--830 ppm depending on operating conditions and interfacial properties. For emulsions with high surfactant content, simultaneous operation of a hydrophobic and hydrophilic membrane, or simultaneous membrane separation with electric demulsification was more efficient in obtaining complete phase separation.« less

An Operational Wake Vortex Sensor Using Pulsed Coherent Lidar

NASA Technical Reports Server (NTRS)

Barker, Ben C., Jr.; Koch, Grady J.; Nguyen, D. Chi

1998-01-01

NASA and FAA initiated a program in 1994 to develop methods of setting spacings for landing aircraft by incorporating information on the real-time behavior of aircraft wake vortices. The current wake separation standards were developed in the 1970's when there was relatively light airport traffic and a logical break point by which to categorize aircraft. Today's continuum of aircraft sizes and increased airport packing densities have created a need for re-evaluation of wake separation standards. The goals of this effort are to ensure that separation standards are adequate for safety and to reduce aircraft spacing for higher airport capacity. Of particular interest are the different requirements for landing under visual flight conditions and instrument flight conditions. Over the years, greater spacings have been established for instrument flight than are allowed for visual flight conditions. Preliminary studies indicate that the airline industry would save considerable money and incur fewer passenger delays if a dynamic spacing system could reduce separations at major hubs during inclement weather to the levels routinely achieved under visual flight conditions. The sensor described herein may become part of this dynamic spacing system known as the "Aircraft VOrtex Spacing System" (AVOSS) that will interface with a future air traffic control system. AVOSS will use vortex behavioral models and short-term weather prediction models in order to predict vortex behavior sufficiently into the future to allow dynamic separation standards to be generated. The wake vortex sensor will periodically provide data to validate AVOSS predictions. Feasibility of measuring wake vortices using a lidar was first demonstrated using a continuous wave (CW) system from NASA Marshall Space Flight Sensor and tested at the Volpe National Transportation Systems Center's wake vortex test site at JFK International Airport. Other applications of CW lidar for wake vortex measurement have been made more recently, including a system developed by the MIT Lincoln Laboratory. This lidar has been used for detailed measurements of wake vortex velocities in support of wake vortex model validation. The first measurements of wake vortices using a pulsed, lidar were made by Coherent Technologies, Inc. (CTI) using a 2 micron solid-state, flashlamp-pumped system operating at 5 Hz. This system was first deployed at Denver's Stapleton Airport. Pulsed lidar has been selected as the baseline technology for an operational sensor due to its longer range capability.

Emulsion characteristics, chemical and textural properties of meat systems produced with double emulsions as beef fat replacers.

PubMed

Serdaroğlu, Meltem; Öztürk, Burcu; Urgu, Müge

2016-07-01

In recent years, double emulsions are stated to have a promising potential in low-fat food production, however, there are very few studies on their possible applications in meat matrices. We aimed to investigate the quality of beef emulsion systems in which beef fat was totally replaced by double emulsions (W1/O/W2) prepared with olive oil and sodium caseinate (SC) by two-step emulsification procedure. Incorporation of W1/O/W2 emulsion resulted in reduced lipid, increased protein content, and modified fatty acid composition. W1/O/W2 emulsion treatments had lower jelly and fat separation, higher water-holding capacity and higher emulsion stability than control samples with beef fat. Increased concentrations of W1/O/W2 emulsions resulted in significant changes in texture parameters. TBA values were lower in W1/O/W2 emulsion treatments than control treatment after 60days of storage. In conclusion, our study confirms that double emulsions had promising impacts on modifying fatty acid composition and developing both technologically and oxidatively stable beef emulsion systems. Copyright © 2016 Elsevier Ltd. All rights reserved.

Microbubble Fabrication of Concave-porosity PDMS Beads

PubMed Central

Bertram, John R.; Nee, Matthew J.

2015-01-01

Microbubble fabrication (by use of a fine emulsion) provides a means of increasing the surface-area-to-volume (SAV) ratio of polymer materials, which is particularly useful for separations applications. Porous polydimethylsiloxane (PDMS) beads can be produced by heat-curing such an emulsion, allowing the interface between the aqueous and aliphatic phases to mold the morphology of the polymer. In the procedures described here, both polymer and crosslinker (triethoxysilane) are sonicated together in a cold-bath sonicator. Following a period of cross-linking, emulsions are added dropwise to a hot surfactant solution, allowing the aqueous phase of the emulsion to separate, and forming porous polymer beads. We demonstrate that this method can be tuned, and the SAV ratio optimized, by adjusting the electrolyte content of the aqueous phase in the emulsion. Beads produced in this way are imaged with scanning electron microscopy, and representative SAV ratios are determined using Brunauer–Emmett–Teller (BET) analysis. Considerable variability with the electrolyte identity is observed, but the general trend is consistent: there is a maximum in SAV obtained at a specific concentration, after which porosity decreases markedly. PMID:26709997

Effect of irradiated pork on physicochemical properties of meat emulsions

NASA Astrophysics Data System (ADS)

Choi, Yun-Sang; Sung, Jung-Min; Jeong, Tae-Jun; Hwang, Ko-Eun; Song, Dong-Heon; Ham, Youn-Kyung; Kim, Hyun-Wook; Kim, Young-Boong; Kim, Cheon-Jei

2016-02-01

The effect of pork irradiated with doses up to 10 kGy on meat emulsions formulated with carboxy methyl cellulose (CMC) was investigated. Raw pork was vacuums packaged at a thickness of 2.0 cm and irradiated by X-ray linear accelerator (15 kW, 5 MeV). The emulsion had higher lightness, myofibrillar protein solubility, total protein solubility, and apparent viscosity with increasing doses, whereas cooking loss, total expressible fluid separation, and hardness decreased. There were no significant differences in fat separation, sarcoplasmic protein solubility, springiness, and cohesiveness. Our results indicated that it is treatment by ionizing radiation which causes the effects the physicochemical properties of the final raw meat product.

A low-cost mullite-titania composite ceramic hollow fiber microfiltration membrane for highly efficient separation of oil-in-water emulsion.

PubMed

Zhu, Li; Chen, Mingliang; Dong, Yingchao; Tang, Chuyang Y; Huang, Aisheng; Li, Lingling

2016-03-01

Oil-in-water (O/W) emulsion is considered to be difficult to treat. In this work, a low-cost multi-layer-structured mullite-titania composite ceramic hollow fiber microfiltration membrane was fabricated and utilized to efficiently remove fine oil droplets from (O/W) emulsion. In order to reduce membrane cost, coal fly ash was effectively recycled for the first time to fabricate mullite hollow fiber with finger-like and sponge-like structures, on which a much more hydrophilic TiO2 layer was further deposited. The morphology, crystalline phase, mechanical and surface properties were characterized in details. The filtration capability of the final composite membrane was assessed by the separation of a 200 mg·L(-1) synthetic (O/W) emulsion. Even with this microfiltration membrane, a TOC removal efficiency of 97% was achieved. Dilute NaOH solution backwashing was used to effectively accomplish membrane regeneration (∼96% flux recovery efficiency). This study is expected to guide an effective way to recycle waste coal fly ash not only to solve its environmental problems but also to produce a high-valued mullite hollow fiber membrane for highly efficient separation application of O/W emulsion with potential simultaneous functions of pure water production and oil resource recovery. Copyright © 2015 Elsevier Ltd. All rights reserved.

Flow Separation Control Over a Ramp Using Sweeping Jet Actuators

NASA Technical Reports Server (NTRS)

Koklu, Mehti; Owens, Lewis R.

2014-01-01

Flow separation control on an adverse-pressure-gradient ramp model was investigated using various flow-control methods in the NASA Langley 15-Inch Wind Tunnel. The primary flow-control method studied used a sweeping jet actuator system to compare with more classic flow-control techniques such as micro-vortex generators, steady blowing, and steady- and unsteady-vortex generating jets. Surface pressure measurements and a new oilflow visualization technique were used to characterize the effects of these flow-control actuators. The sweeping jet actuators were run in three different modes to produce steady-straight, steady-angled, and unsteady-oscillating jets. It was observed that all of these flow-control methods are effective in controlling the separated flows on the ramp model. The steady-straight jet energizes the boundary layer by momentum addition and was found to be the least effective method for a fixed momentum coefficient. The steady-angled jets achieved better performance than the steady-straight jets because they generate streamwise vortices that energize the boundary layer by mixing high-momentum fluid with near wall low-momentum fluid. The unsteady-oscillating jets achieved the best performance by increasing the pressure recovery and reducing the downstream flow separation. Surface flow visualizations indicated that two out-of-phase counter-rotating vortices are generated per sweeping jet actuator, while one vortex is generated per vortex-generating jets. The extra vortex resulted in increased coverage, more pressure recovery, and reduced flow separation.

A comparison with theory of peak to peak sound level for a model helicopter rotor generating blade slap at low tip speeds

NASA Technical Reports Server (NTRS)

Fontana, R. R.; Hubbard, J. E., Jr.

1983-01-01

Mini-tuft and smoke flow visualization techniques have been developed for the investigation of model helicopter rotor blade vortex interaction noise at low tip speeds. These techniques allow the parameters required for calculation of the blade vortex interaction noise using the Widnall/Wolf model to be determined. The measured acoustics are compared with the predicted acoustics for each test condition. Under the conditions tested it is determined that the dominating acoustic pulse results from the interaction of the blade with a vortex 1-1/4 revolutions old at an interaction angle of less than 8 deg. The Widnall/Wolf model predicts the peak sound pressure level within 3 dB for blade vortex separation distances greater than 1 semichord, but it generally over predicts the peak S.P.L. by over 10 dB for blade vortex separation distances of less than 1/4 semichord.

Microfluidic control of droplet formation from stable emulsions formed by aqueous two-phase systems

NASA Astrophysics Data System (ADS)

Teixeira, Alyne G.; Tsai, Meng-Chiao; Frampton, John P.

2018-02-01

Aqueous two-phase systems (ATPSs) form from the thermodynamic separation of two dissolved incompatible solutes, such as two polymers, a polymer and a salt, and a polymer and a surfactant. At most supercritical concentrations, ATPS emulsions can be formed by vigorous mixing. These emulsions typically settle into distinct layers in minutes to hours. However, it is also possible to choose ATPS compositions with extremely long settling times that resemble stable emulsions. Here, we generated stable emulsions from a polyethylene glycol (PEG)-dextran ATPS by selecting ATPS compositions at the extreme ends of the tie lines connecting the binodal curve delineating phase-separating compositions. Droplets of PEG in a continuous dextran phase did not coalesce appreciably over the course of several days when stored in a conical tube or syringe. However, upon exposure to laminar flow conditions in a microfluidic channel, droplets were observed to coalesce. Through microscopic characterization of droplet volume, an increase in droplet size and decrease in overall droplet number was observed as a function of channel distance, suggesting a progressive droplet merging phenomenon. This novel approach to control droplet size by encouraging coalescence of stable emulsions under laminar flow in a microfluidic channel enables the production of droplets ranging from fL to several pL, which may enable various future biotechnology applications.

Schizophrenic Diblock-Copolymer-Functionalized Nanoparticles as Temperature-Responsive Pickering Emulsifiers.

PubMed

Ranka, Mikhil; Katepalli, Hari; Blankschtein, Daniel; Hatton, T Alan

2017-11-21

Stimuli-responsive pickering emulsions have received considerable attention in recent years, and the utilization of temperature as a stimulus has been of particular interest. Previous efforts have led to responsive systems that enable the formation of stable emulsions at room temperature, which can subsequently be triggered to destabilize with an increase in temperature. The development of a thermoresponsive system that exhibits the opposite response, however, i.e., one that can be triggered to form stable emulsions at elevated temperatures and subsequently be induced to phase separate at lower temperatures, has so far been lacking. Here, we describe a system that accomplishes this goal by leveraging a schizophrenic diblock copolymer that exhibits both an upper and a lower critical solution temperature. The diblock copolymer was conjugated to 20 nm silica nanoparticles, which were subsequently demonstrated to stabilize O/W emulsions at 65 °C and trigger phase separation upon cooling to 25 °C. The effects of particle concentration, electrolyte concentration, and polymer architecture were investigated, and facile control of emulsion stability was demonstrated for multiple oil types. Our approach is likely to be broadly adaptable to other schizophrenic diblock copolymers and find significant utility in applications such as enhanced oil recovery and liquid-phase heterogeneous catalysis, where stable emulsions are desired only at elevated temperatures.

A comparative study of full Navier-Stokes and Reduced Navier-Stokes analyses for separating flows within a diffusing inlet S-duct

NASA Technical Reports Server (NTRS)

Anderson, B. H.; Reddy, D. R.; Kapoor, K.

1993-01-01

A three-dimensional implicit Full Navier-Stokes (FNS) analysis and a 3D Reduced Navier-Stokes (RNS) initial value space marching solution technique has been applied to a class of separate flow problems within a diffusing S-duct configuration characterized as vortex-liftoff. Both Full Navier-Stokes and Reduced Navier-Stokes solution techniques were able to capture the overall flow physics of vortex lift-off, however more consideration must be given to the development of turbulence models for the prediction of the locations of separation and reattachment. This accounts for some of the discrepancies in the prediction of the relevant inlet distortion descriptors, particularly circumferential distortion. The 3D RNS solution technique adequately described the topological structure of flow separation associated with vortex lift-off.

Numerical research of the swirling supersonic gas flows in the self-vacuuming vortex tube

NASA Astrophysics Data System (ADS)

Volov, V. T.; Lyaskin, A. S.

2018-03-01

This article presents the results of simulation for a special type of vortex tubes – self-vacuuming vortex tube (SVVT), for which extreme values of temperature separation and vacuum are realized. The main results of this study are the flow structure in the SVVT and energy loss estimations on oblique shock waves, gas friction, instant expansion and organization of vortex bundles in SVVT.

Phospholipid hydrolysis in a pharmaceutical emulsion assessed by physicochemical parameters and a new analytical method.

PubMed

Rabinovich-Guilatt, Laura; Dubernet, Catherine; Gaudin, Karen; Lambert, Gregory; Couvreur, Patrick; Chaminade, Pierre

2005-09-01

The aim of this work was to develop a simple high-performance liquid chromatography (HPLC) technique with evaporative light scattering detection (ELSD) for the separation and quantification of the major phospholipid (PL) and lysophospholipid (LPL) classes contained in a pharmaceutical phospholipid-based emulsion. In the established method, phosphatidylcholine (PC), phosphatidylethanolamine (PE), sphingomyeline (SM), lysophosphatidylcholine (LPC) and lysophosphatidylethanolamine (LPE) were separated with a PVA-Sil stationary phase and a binary gradient from pure chloroform to methanol:water (94:6 v/v) at 3.4%/min. The ELSD detection was enhanced using 0.1% triethylamine and formic acid in each gradient mobile phases. Factors such as stationary phase and ELSD drift tube temperature were optimized, concluding in optimal temperatures of 25 degrees C for separation and 50 degrees C for evaporation. This HPLC-ELSD method was then applied to a PL-emulsion exposed to autoclaving and accelerated thermal conditions at 50 degrees C. Hydrolysis of PC and PE followed first-order kinetics, representing only 45% of the total lipid mass after 3 months. The chemical stability was correlated to commonly measured formulation physical and physico-chemical parameters such as droplet size, emulsion pH and zeta-potential.

Technical Evaluation Report, Part A - Vortex Flow and High Angle of Attack

NASA Technical Reports Server (NTRS)

Luckring, James M.

2003-01-01

A symposium entitled Vortex Flow and High Angle of Attack was held in Loen, Norway, from May 7 through May 11, 2001. The Applied Vehicle Technology (AVT) panel, under the auspices of the Research and Technology Organization (RTO), sponsored this symposium. Forty-eight papers, organized into nine sessions, addressed computational and experimental studies of vortex flows pertinent to both aircraft and maritime applications. The studies also ranged from fundamental fluids investigations to flight test results, and significant results were contributed from a broad range of countries. The principal emphasis of this symposium was on "the understanding and prediction of separation-induced vortex flows and their effects on military vehicle performance, stability, control, and structural design loads." It was further observed by the program committee that "separation- induced vortex flows are an important part of the design and off-design performance of conventional fighter aircraft and new conventional or unconventional manned or unmanned advanced vehicle designs (UAVs, manned aircraft, missiles, space planes, ground-based vehicles, and ships)." The nine sessions addressed the following topics: vortical flows on wings and bodies, experimental techniques for vortical flows, numerical simulations of vortical flows, vortex stability and breakdown, vortex flows in maritime applications, vortex interactions and control, vortex dynamics, flight testing, and vehicle design. The purpose of this paper is to provide brief reviews of these papers along with some synthesizing perspectives toward future vortex flow research opportunities. The paper includes the symposium program. (15 refs.)

Vortex shedding within laminar separation bubbles forming over an airfoil

NASA Astrophysics Data System (ADS)

Kirk, Thomas M.; Yarusevych, Serhiy

2017-05-01

Vortex shedding within laminar separation bubbles forming over the suction side of a NACA 0018 airfoil is studied through a combination of high-speed flow visualization and boundary layer measurements. Wind tunnel experiments are performed at a chord-based Reynolds number of 100,000 and four angles of attack. The high-speed flow visualization is complemented by quantitative velocity and surface pressure measurements. The structures are shown to originate from the natural amplification of small-amplitude disturbances, and the shear layer roll-up is found to occur coherently across the span. However, significant cycle-to-cycle variations are observed in vortex characteristics, including shedding period and roll-up location. The formation of the roll-up vortices precedes the later stages of transition, during which these structures undergo significant deformations and breakdown to smaller scales. During this stage of flow development, vortex merging is also observed. The results provide new insight into the development of coherent structures in separation bubbles and their relation to the overall bubble dynamics and mean bubble topology.

46 CFR 162.050-20 - Separator and bilge alarm test fluids.

Code of Federal Regulations, 2011 CFR

2011-10-01

... mixture of an oil-in-fresh water emulsion, where 1 kg of the mixture consists of: (i) 947.8 g of fresh...; (6) To establish a stable emulsion keep running the centrifugal pump B for one hour and confirm no...

46 CFR 162.050-20 - Separator and bilge alarm test fluids.

Code of Federal Regulations, 2012 CFR

2012-10-01

... mixture of an oil-in-fresh water emulsion, where 1 kg of the mixture consists of: (i) 947.8 g of fresh...; (6) To establish a stable emulsion keep running the centrifugal pump B for one hour and confirm no...

46 CFR 162.050-20 - Separator and bilge alarm test fluids.

Code of Federal Regulations, 2014 CFR

2014-10-01

... mixture of an oil-in-fresh water emulsion, where 1 kg of the mixture consists of: (i) 947.8 g of fresh...; (6) To establish a stable emulsion keep running the centrifugal pump B for one hour and confirm no...

46 CFR 162.050-20 - Separator and bilge alarm test fluids.

Code of Federal Regulations, 2013 CFR

2013-10-01

... mixture of an oil-in-fresh water emulsion, where 1 kg of the mixture consists of: (i) 947.8 g of fresh...; (6) To establish a stable emulsion keep running the centrifugal pump B for one hour and confirm no...

Control of low-speed turbulent separated flow over a backward-facing ramp. Ph.D. Thesis - Old Dominion Univ.

NASA Technical Reports Server (NTRS)

Lin, John C.

1992-01-01

The relative performance and flow phenomena associated with several devices for controlling turbulent separated flow were investigated at low speeds. Relative performance of the devices was examined for flow over a curved, backward-facing ramp in a wind tunnel, and the flow phenomena were examined in a water tunnel using dye-flow visualization. Surface static pressure measurements and oil-flow visualization results from the wind tunnel tests indicated that transverse grooves, longitudinal grooves, submerged vortex generators, vortex generator jets (VGJ's), Viets' fluidic flappers, elongated arches at positive angle of attack, and large-eddy breakup devices (LEBU's) at positive angle of attack placed near the baseline separation location reduce flow separation and increase pressure recovery. Spanwise cylinders reduce flow separation but decrease pressure recovery downstream. Riblets, passive porous surfaces, swept grooves, Helmholtz resonators, and arches and LEBU's with angle of attack less than or = 0 degrees had no significant effect in reducing the extent of the separation region. Wall-cooling computations indicated that separation delay on a partially-cooled ramp is nearly the same as on a fully-cooled ramp, while minimizing the frictional drag increase associated with the wall cooling process. Dry-flow visualization tests in the water tunnel indicated that wishbone vortex generators in the forward orientation shed horseshoe vortices; wishbone vortex generators oriented in the reverse direction and doublet vortex generators shed streamwise counterrotating vortices; a spanewise cylinder located near the wall and LEBU's at angle of attack = -10 degrees produced eddies or transverse vortices which rotated with the same sign as the mean vorticity in a turbulent boundary layer; and the most effective VGJ's produced streamwise co-rotating vortices. Comparative wind-tunnel test results indicated that transferring momentum from the outer region of a turbulent boundary layer through the action of embedded streamwise vortices is more effective than by transverse vortices for the separation control application studied herein.

New Technology for Oil/Water Emulsion Treatment: Phases I and II

DTIC Science & Technology

1998-05-15

m.(Aŕ) Emulsions have long been of practical interest because of their extensive everyday applications. Emulsions are used in foods ( milk and...separating cream from milk . Valve-discharge centrifuges periodically discharge accumulated solids. Split-bowl centrifuges have a bowl that allows...fresh air. Call a physician. RVF CONTACT: Flush with water for 15 minutes. Call a physician. Wash thSroSghly with soap and rinse with water. Call

Certainties and Uncertainties in CFD Prediction of the End of the Vortex Behaviour in Centrifugal Separators

NASA Astrophysics Data System (ADS)

Pisarev, Gleb I.; Hoffmann, Alex C.

2011-09-01

This paper compares CFD simulations of the `end of the vortex' (EoV) behaviour in centrifugal separators with experiment. The EoV was studied in `swirl tubes', cylindrical cyclone separators with swirl vanes. We refer to the EoV as the phenomenon whereby the core of the vortex does not reach the bottom of the separator, but deviates from the swirl tube axis and attaches to the wall, where it rotates at some level above the bottom. The crucial parameters governing the EoV are geometrical, specifically the ratio of the separator length to its diameter (L/D), and operational, specifically the fluid flowrate. Swirl tubes with varying body lengths have been studied experimentally and numerically. CFD simulations were carried out using the commercial package Star-CD. The 3-D Navier-Stokes equations were solved using the finite volume method based on the SIMPLE pressure-correction algorithm and the LES turbulence model. The vortex behaviour was very similar between the experiments and the numerical simulations, this agreement being both qualitative and quantitative. However, there were some cases where the CFD predictions showed only qualitative agreement with experiments, with some of the parameter-values delimiting given types of flows being somewhat different between experiment and simulations.

Robotic Enrichment Processing of Roche 454 Titanium Emlusion PCR at the DOE Joint Genome Institute

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamilton, Matthew; Wilson, Steven; Bauer, Diane

2010-05-28

Enrichment of emulsion PCR product is the most laborious and pipette-intensive step in the 454 Titanium process, posing the biggest obstacle for production-oriented scale up. The Joint Genome Institute has developed a pair of custom-made robots based on the Microlab Star liquid handling deck manufactured by Hamilton to mediate the complexity and ergonomic demands of the 454 enrichment process. The robot includes a custom built centrifuge, magnetic deck positions, as well as heating and cooling elements. At present processing eight emulsion cup samples in a single 2.5 hour run, these robots are capable of processing up to 24 emulsion cupmore » samples. Sample emulsions are broken using the standard 454 breaking process and transferred from a pair of 50ml conical tubes to a single 2ml tube and loaded on the robot. The robot performs the enrichment protocol and produces beads in 2ml tubes ready for counting. The robot follows the Roche 454 enrichment protocol with slight exceptions to the manner in which it resuspends beads via pipette mixing rather than vortexing and a set number of null bead removal washes. The robotic process is broken down in similar discrete steps: First Melt and Neutralization, Enrichment Primer Annealing, Enrichment Bead Incubation, Null Bead Removal, Second Melt and Neutralization and Sequencing Primer Annealing. Data indicating our improvements in enrichment efficiency and total number of bases per run will also be shown.« less

Separator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ashbrook, C.L.

1970-09-22

A separator consists of a housing having an upper fluid inlet and a lower fluid outlet in the sides of the housing. An inverted conical tube is disposed internally of the housing and is in fluid communication with the fluid inlet. The upper fluid inlet tangentially intersects the inverted conical tube so as to create a rotating vortex upon introduction of the mixture. Axially disposed within the vortex tube at the upper end is a withdrawal tube for removing lighter mixture components that are drawn toward the center of the tube. At the lower end of the vortex tube ismore » an adjustable impact plate for transmitting a concussion wave through the vortexed body, so as to cause cavitation. Heavier mixture components gravitate toward the lower fluid outlet and are withdrawn through it. (7 claims)« less

Some observations of separated flow on finite wings

NASA Technical Reports Server (NTRS)

Winkelmann, A. E.; Ngo, H. T.; De Seife, R. C.

1982-01-01

Wind tunnel test results for aspects of flow over airfoils exhibiting single and multiple trailing edge stall 'mushroom' cells are reported. Rectangular wings with aspect ratios of 4.0 and 9.0 were tested at Reynolds numbers of 480,000 and 257,000, respectively. Surface flow patterns were visualized by means of a fluorescent oil flow technique, separated flow was observed with a tuft wand and a water probe, spanwise flow was studied with hot-wire anemometry, smoke flow and an Ar laser illuminated the centerplane flow, and photographs were made of the oil flow patterns. Swirl patterns on partially and fully stalled wings suggested vortex flow attachments in those regions, and a saddle point on the fully stalled AR=4.0 wing indicated a secondary vortex flow at the forward region of the separation bubble. The separation wake decayed downstream, while the tip vortex interacted with the separation bubble on the fully stalled wing. Three mushroom cells were observed on the AR=9.0 wing.

A new solution to emulsion liquid membrane problems by non-Newtonian conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skelland, A.H.P.; Meng, X.

1996-02-01

Surfactant-stabilized emulsion liquid membrane processes constitute an emerging separation technology that has repeatedly been shown to be highly suited for such diverse separation processes as metal recovery or removal from dilute aqueous solutions; separations in the food industry; removal of organic bases and acids from water; and separation of hydrocarbons. Emulsion liquid membrane separation processes remain excessively vulnerable to one or more of four major problems. Difficulties lie in developing liquid membranes that combine high levels of both stability and permeability with acceptably low levels of swelling and ease of subsequent demulsification for membrane and solute recovery. This article providesmore » a new technique for simultaneously overcoming the first three problems, while identifying physical indications that the proposed solution may have little adverse effect on the fourth problem (demulsification) and may even alleviate it. Numerous benefits of optimized conversion of the membrane phase into suitable non-Newtonian form are identified, their mechanisms outlined, and experimental verifications provided. These include increased stability, retained (or enhanced) permeability, reduced swelling, increased internal phase volume, and increased stirrer speeds. The highly favorable responsiveness of both aliphatic and aromatic membranes to the new technique is demonstrated.« less

Purification of trona ores by conditioning with an oil-in-water emulsion

DOEpatents

Miller, J. D.; Wang, Xuming; Li, Minhua

2009-04-14

The present invention is a trona concentrate and a process for floating gangue material from trona ore that comprises forming an emulsion, conditioning the trona ore at a high solids content in a saturated trona suspension, and then floating and removing the gangue material. The process for separating trona from gangue materials in trona ore can include emulsifying an oil in an aqueous solution to form an oil-in-water emulsion. A saturated trona suspension having a high solids content can also be formed having trona of a desired particle size. The undissolved trona in the saturated suspension can be conditioned by mixing the saturated suspension and the oil-in-water emulsion to form a conditioning solid suspension of trona and gangue material. A gas can be injected through the conditioning solid suspension to float the gangue material. Thus, the floated gangue material can be readily separated from the trona to form a purified trona concentrate without requirements of additional heat or other expensive processing steps.

In-flight flow visualization results from the X-29A aircraft at high angles of attack

NASA Technical Reports Server (NTRS)

Delfrate, John H.; Saltzman, John A.

1992-01-01

Flow visualization techniques were used on the X-29A aircraft at high angles of attack to study the vortical flow off the forebody and the surface flow on the wing and tail. The forebody vortex system was studied because asymmetries in the vortex system were suspected of inducing uncommanded yawing moments at zero sideslip. Smoke enabled visualization of the vortex system and correlation of its orientation with flight yawing moment data. Good agreement was found between vortex system asymmetries and the occurrence of yawing moments. Surface flow on the forward-swept wing of the X-29A was studied using tufts and flow cones. As angle of attack increased, separated flow initiated at the root and spread outboard encompassing the full wing by 30 deg angle of attack. In general, the progression of the separated flow correlated well with subscale model lift data. Surface flow on the vertical tail was also studied using tufts and flow cones. As angle of attack increased, separated flow initiated at the root and spread upward. The area of separated flow on the vertical tail at angles of attack greater than 20 deg correlated well with the marked decrease in aircraft directional stability.

Evaluation of stability and viscosity measurement of emulsion from oil from production in northern oilfield in Thailand

NASA Astrophysics Data System (ADS)

Juntarasakul, O.; Maneeintr, K.

2018-04-01

Emulsion is normally present in oil due to the mixing occurring during oil recovery. The formation of emulsion can cause some problems in production and transportation. Viscosity and stability of emulsion play a key roles in oil transportation and separation to meet sales specification. Therefore, the aims of this research are to measure the viscosity of oil an emulsion and to evaluate the stability of emulsion of light oil from Fang oilfield in Thailand. The parameters of this study are temperature, shear rate and water cut ranging from 50 to 80 °C, 3.75 to 70 s-1 and 0 to 60%, respectively. These effects of parameters on viscosity and stability of emulsion are required for the design of the process and to increase oil production with various conditions. The results shows that viscosity decreases as temperature and shear rate increase. In contrast, viscosity becomes higher when water cut is lower. Furthermore, droplet sizes of water-in-oil emulsion at different conditions are investigated the stability of emulsion. The droplet sizes become smaller when high shear rate is applied and emulsion becomes more stable. Furthermore, correlations are developed to predict the viscosity and stability of the oil and emulsion from Thailand.

Flow structure generated by perpendicular blade-vortex interaction and implications for helicopter noise prediction. Volume 1: Measurements

NASA Technical Reports Server (NTRS)

Wittmer, Kenneth S.; Devenport, William J.

1996-01-01

The perpendicular interaction of a streamwise vortex with an infinite span helicopter blade was modeled experimentally in incompressible flow. Three-component velocity and turbulence measurements were made using a sub-miniature four sensor hot-wire probe. Vortex core parameters (radius, peak tangential velocity, circulation, and centerline axial velocity deficit) were determined as functions of blade-vortex separation, streamwise position, blade angle of attack, vortex strength, and vortex size. The downstream development of the flow shows that the interaction of the vortex with the blade wake is the primary cause of the changes in the core parameters. The blade sheds negative vorticity into its wake as a result of the induced angle of attack generated by the passing vortex. Instability in the vortex core due to its interaction with this negative vorticity region appears to be the catalyst for the magnification of the size and intensity of the turbulent flowfield downstream of the interaction. In general, the core radius increases while peak tangential velocity decreases with the effect being greater for smaller separations. These effects are largely independent of blade angle of attack; and if these parameters are normalized on their undisturbed values, then the effects of the vortex strength appear much weaker. Two theoretical models were developed to aid in extending the results to other flow conditions. An empirical model was developed for core parameter prediction which has some rudimentary physical basis, implying usefulness beyond a simple curve fit. An inviscid flow model was also created to estimate the vorticity shed by the interaction blade, and to predict the early stages of its incorporation into the interacting vortex.

A user-friendly and scalable process to prepare a ready-to-use inactivated vaccine: the example of heartwater in ruminants under tropical conditions.

PubMed

Marcelino, Isabel; Lefrançois, Thierry; Martinez, Dominique; Giraud-Girard, Ken; Aprelon, Rosalie; Mandonnet, Nathalie; Gaucheron, Jérôme; Bertrand, François; Vachiéry, Nathalie

2015-01-29

The use of cheap and thermoresistant vaccines in poor tropical countries for the control of animal diseases is a key issue. Our work aimed at designing and validating a process for the large-scale production of a ready-to-use inactivated vaccine for ruminants. Our model was heartwater caused by the obligate intracellular bacterium Ehrlichia ruminantium (ER). The conventional inactivated vaccine against heartwater (based on whole bacteria inactivated with sodium azide) is prepared immediately before injection, using a syringe-extrusion method with Montanide ISA50. This is a fastidious time-consuming process and it limits the number of vaccine doses available. To overcome these issues, we tested three different techniques (syringe, vortex and homogenizer) and three Montanide ISA adjuvants (50, 70 and 70M). High-speed homogenizer was the optimal method to emulsify ER antigens with both ISA70 and 70M adjuvants. The emulsions displayed a good homogeneity (particle size below 1 μm and low phase separation), conductivity below 10 μS/cm and low antigen degradation at 4 °C for up to 1 year. The efficacy of the different formulations was then evaluated during vaccination trials on goats. The inactivated ER antigens emulsified with ISA70 and ISA70M in a homogenizer resulted in 80% and 100% survival rates, respectively. A cold-chain rupture assay using ISA70M+ER was performed to mimic possible field conditions exposing the vaccine at 37 °C for 4 days before delivery. Surprisingly, the animal survival rate was still high (80%). We also observed that the MAP-1B antibody response was very similar between animals vaccinated with ISA70+ER and ISA70M+ER emulsions, suggesting a more homogenous antigen distribution and presentation in these emulsions. Our work demonstrated that the combination of ISA70 or ISA70M and homogenizer is optimal for the production of an effective ready-to-use inactivated vaccine against heartwater, which could easily be produced on an industrial scale. Copyright © 2014 Elsevier Ltd. All rights reserved.

Application of the vortex-lattice technique to the analysis of thin wings with vortex separation and thick multi-element wings

NASA Technical Reports Server (NTRS)

Smith, C. W.; Bhateley, I. C.

1976-01-01

Two techniques for extending the range of applicability of the basic vortex-lattice method are discussed. The first improves the computation of aerodynamic forces on thin, low-aspect-ratio wings of arbitrary planforms at subsonic Mach numbers by including the effects of leading-edge and tip vortex separation, characteristic of this type wing, through use of the well-known suction-analogy method of E. C. Polhamus. Comparisons with experimental data for a variety of planforms are presented. The second consists of the use of the vortex-lattice method to predict pressure distributions over thick multi-element wings (wings with leading- and trailing-edge devices). A method of laying out the lattice is described which gives accurate pressures on the top and part of the bottom surface of the wing. Limited comparisons between the result predicted by this method, the conventional lattice arrangement method, experimental data, and 2-D potential flow analysis techniques are presented.

Recent theoretical developments and experimental studies pertinent to vortex flow aerodynamics - With a view towards design

NASA Technical Reports Server (NTRS)

Lamar, J. E.; Luckring, J. M.

1978-01-01

A review is presented of recent progress in a research program directed towards the development of an improved vortex-flow technology base. It is pointed out that separation induced vortex-flows from the leading and side edges play an important role in the high angle-of-attack aerodynamic characteristics of a wide range of modern aircraft. In the analysis and design of high-speed aircraft, a detailed knowledge of this type of separation is required, particularly with regard to critical wind loads and the stability and performance at various off-design conditions. A description of analytical methods is presented. The theoretical methods employed are divided into two classes which are dependent upon the underlying aerodynamic assumptions. One conical flow method is considered along with three different nonconical flow methods. Comparisons are conducted between the described methods and available aerodynamic data. Attention is also given to a vortex flow drag study and a vortex flow wing design using suction analogy.

Dispersion Stability of O/W Emulsions with Different Oil Contents Under Various Freezing and Thawing Conditions.

PubMed

Katsuki, Kazutaka; Miyagawa, Yayoi; Nakagawa, Kyuya; Adachi, Shuji

2017-07-01

Freezing and thawing of oil-in-water (O/W) emulsion-type foods bring about oil-water separation and deterioration; hence, the effects of freezing and thawing conditions on the destabilization of O/W emulsions were examined. The freezing rate and thawing temperature hardly affected the stability of the O/W emulsion. O/W emulsions having different oil fractions were stored at temperatures ranging from -30 to -20 °C and then thawed. The stability after thawing depended on the storage temperature, irrespective of the oil fraction of the emulsion. A good correlation was found between the time at which the stability began to decrease and the time taken for the oil to crystalize. These results indicated that the dominant cause for the destabilization of the O/W emulsion during freezing and thawing is the crystallization of the oil phase and that the effects of the freezing and thawing rates on the stability are insignificant. © 2017 Institute of Food Technologists®.

Rejuvenation of Spent Media via Supported Emulsion Liquid Membranes

NASA Technical Reports Server (NTRS)

Wiencek, John M.

2002-01-01

The overall goal of this project was to maximize the reuseability of spent fermentation media. Supported emulsion liquid membrane separation, a highly efficient extraction technique, was used to remove inhibitory byproducts during fermentation; thus, improve the yield while reducing the need for fresh water. The key objectives of this study were: (1) Develop an emulsion liquid membrane system targeting low molecular weight organic acids which has minimal toxicity on a variety of microbial systems. (2) Conduct mass transfer studies to allow proper modeling and design of a supported emulsion liquid membrane system. (3) Investigate the effect of gravity on emulsion coalescence within the membrane unit. (4) Access the effect of water re-use on fermentation yields in a model microbial system. and (5) Develop a perfusion-type fermentor utilizing a supported emulsion liquid membrane system to control inhibitory fermentation byproducts (not completed due to lack of funds)

One-step formation of w/o/w multiple emulsions stabilized by single amphiphilic block copolymers.

PubMed

Hong, Liangzhi; Sun, Guanqing; Cai, Jinge; Ngai, To

2012-02-07

Multiple emulsions are complex polydispersed systems in which both oil-in-water (O/W) and water-in-oil (W/O) emulsion exists simultaneously. They are often prepared accroding to a two-step process and commonly stabilized using a combination of hydrophilic and hydrophobic surfactants. Recently, some reports have shown that multiple emulsions can also be produced through one-step method with simultaneous occurrence of catastrophic and transitional phase inversions. However, these reported multiple emulsions need surfactant blends and are usually described as transitory or temporary systems. Herein, we report a one-step phase inversion process to produce water-in-oil-in-water (W/O/W) multiple emulsions stabilized solely by a synthetic diblock copolymer. Unlike the use of small molecule surfactant combinations, block copolymer stabilized multiple emulsions are remarkably stable and show the ability to separately encapsulate both polar and nonpolar cargos. The importance of the conformation of the copolymer surfactant at the interfaces with regards to the stability of the multiple emulsions using the one-step method is discussed.

Evaluation of emulsion emulsified by starch nanocrystal: A preliminary study

NASA Astrophysics Data System (ADS)

Ahmad, Azfar Al Ariff; Lazim, Azwan Mat

2018-04-01

The starch nanocrystals (SNC) used in this study were made of sago starch and prepared by using sulfuric acid hydrolysis of sago starch. The aim of this study is to look at the potential of SNC as and emulsifier. Previously, the SNC underwent analytical analysis in order to understand and evaluate the isolated SNC. The ability of SNC as emulsifier was further investigated in this study. Emulsions with low, medium and high oil content has been prepared in function of different wt% of SNC. The emulsion stability against coalescence for two weeks has also been studied. Results showed that the emulsions prepared are steadily stable after one weeks of storage without any separation and changes. From the observation, there are two major factor contributed to the formation of emulsion and its stability, the SNC concentration and oil content. Relatively, higher percentage of SNC resulting a higher emulsion index, whereas no emulsion was formed if oil content exceeding 50% of the systems. The most suitable formulation to prepare Pickering Emulsion is the oil content around 45% and SNC concentration around 2 - 4%.

Flow Control on Low-Pressure Turbine Airfoils Using Vortex Generator Jets

NASA Technical Reports Server (NTRS)

Volino, Ralph J.; Ibrahim, Mounir B.; Kartuzova, Olga

2010-01-01

Motivation - Higher loading on Low-Pressure Turbine (LPT) airfoils: Reduce airfoil count, weight, cost. Increase efficiency, and Limited by suction side separation. Growing understanding of transition, separation, wake effects: Improved models. Take advantage of wakes. Higher lift airfoils in use. Further loading increases may require flow control: Passive: trips, dimples, etc. Active: plasma actuators, vortex generator jets (VGJs). Can increased loading offset higher losses on high lift airfoils. Objectives: Advance knowledge of boundary layer separation and transition under LPT conditions. Demonstrate, improve understanding of separation control with pulsed VGJs. Produce detailed experimental data base. Test and develop computational models.

Comparison of Effects of Separate and Combined Sugammadex and Lipid Emulsion Administration on Hemodynamic Parameters and Survival in a Rat Model of Verapamil Toxicity.

PubMed

Tulgar, Serkan; Kose, Halil Cihan; Demir Piroglu, Isılay; Karakilic, Evvah; Ates, Nagihan Gozde; Demir, Ahmet; Gergerli, Ruken; Guven, Selin; Piroglu, Mustafa Devrim

2016-03-25

Toxicity of calcium channel blockers leads to high patient mortality and there is no effective antidote. The benefit of using 20% lipid emulsion and sugammadex has been reported. The present study measured the effect of sugammadex and 20% lipid emulsion on hemodynamics and survival in a rat model of verapamil toxicity. In this single-blinded randomized control study, rats were separated into 4 groups of 7 rats each: Sugammadex (S), Sugammadex plus 20% lipid emulsion (SL), 20% lipid emulsion (L), and control (C). Heart rates and mean arterial pressures were monitored and noted each minute until death. Average time to death was 21.0±9.57 minutes for group C, 35.57±10.61 minutes for group S, 37.14±16.6 minutes for group L and 49.86±27.56 minutes for group SL. Time to death was significantly longer in other groups than in the control group (p<0.05). Verapamil overdose is has a comparatively high mortality rate and there is no effective antidote. Treatment generally involves gastric decontamination and symptomatic treatment to counteract the drug's negative effects. In animal studies sugammadex and lipid emulsion had a positive effect on survival in patients with calcium channel blocker toxicity. Sugammadex and intralipid increased survival in a rat model of verapamil toxicity. The combination of both drugs may decrease cardiotoxicity. Sugammadex alone or combined with 20% lipid emulsion reduce the need for inotropic agents. The mechanism requires clarification with larger studies.

Comparison of Effects of Separate and Combined Sugammadex and Lipid Emulsion Administration on Hemodynamic Parameters and Survival in a Rat Model of Verapamil Toxicity

PubMed Central

Tulgar, Serkan; Kose, Halil Cihan; Piroglu, Isılay Demir; Karakilic, Evvah; Ates, Nagihan Gozde; Demir, Ahmet; Gergerli, Ruken; Guven, Selin; Piroglu, Mustafa Devrim

2016-01-01

Background Toxicity of calcium channel blockers leads to high patient mortality and there is no effective antidote. The benefit of using 20% lipid emulsion and sugammadex has been reported. The present study measured the effect of sugammadex and 20% lipid emulsion on hemodynamics and survival in a rat model of verapamil toxicity. Material/Methods In this single-blinded randomized control study, rats were separated into 4 groups of 7 rats each: Sugammadex (S), Sugammadex plus 20% lipid emulsion (SL), 20% lipid emulsion (L), and control (C). Heart rates and mean arterial pressures were monitored and noted each minute until death. Results Average time to death was 21.0±9.57 minutes for group C, 35.57±10.61 minutes for group S, 37.14±16.6 minutes for group L and 49.86±27.56 minutes for group SL. Time to death was significantly longer in other groups than in the control group (p<0.05). Conclusions Verapamil overdose is has a comparatively high mortality rate and there is no effective antidote. Treatment generally involves gastric decontamination and symptomatic treatment to counteract the drug’s negative effects. In animal studies sugammadex and lipid emulsion had a positive effect on survival in patients with calcium channel blocker toxicity. Sugammadex and intralipid increased survival in a rat model of verapamil toxicity. The combination of both drugs may decrease cardiotoxicity. Sugammadex alone or combined with 20% lipid emulsion reduce the need for inotropic agents. The mechanism requires clarification with larger studies. PMID:27012816

Helicity conservation under quantum reconnection of vortex rings.

PubMed

Zuccher, Simone; Ricca, Renzo L

2015-12-01

Here we show that under quantum reconnection, simulated by using the three-dimensional Gross-Pitaevskii equation, self-helicity of a system of two interacting vortex rings remains conserved. By resolving the fine structure of the vortex cores, we demonstrate that the total length of the vortex system reaches a maximum at the reconnection time, while both writhe helicity and twist helicity remain separately unchanged throughout the process. Self-helicity is computed by two independent methods, and topological information is based on the extraction and analysis of geometric quantities such as writhe, total torsion, and intrinsic twist of the reconnecting vortex rings.

Evaluation of rotating-cylinder and piston-cylinder reactors for ground-based emulsion polymerization

NASA Technical Reports Server (NTRS)

Vanderhoff, J. W.; El-Aasser, M. S.

1987-01-01

The objectives of this program are to apply ground-based emulsion polymerization reactor technology to improve the production of: monodisperse latex particles for calibration standards, chromatographic separation column packing, and medical research; and commercial latexes such as those used for coatings, foams, and adhesives.

Flight test investigation of the vortex wake characteristics behind a Boeing 727 during two-segment and normal ILS approaches (A joint NASA/FAA report)

NASA Technical Reports Server (NTRS)

Barber, M. R.; Kurkowski, R. L.; Garodz, L. J.; Robinson, G. H.; Smith, H. J.; Jacobsen, R. A.; Stinnett, G. W., Jr.; Mcmurtry, T. C.; Tymczyszyn, J. J.; Devereaux, R. L.

1975-01-01

Flight tests were performed to evaluate the vortex wake characteristics of a Boeing 727 aircraft during conventional and two-segment instrument landing approaches. Smoke generators were used for vortex marking. The vortex was intentionally intercepted by a Lear Jet and a Piper Comanche aircraft. The vortex location during landing approach was measured using a system of phototheodolites. The tests showed that at a given separation distance there are no readily apparent differences in the upsets resulting from deliberate vortex encounters during the two types of approaches. The effect of the aircraft configuration on the extent and severity of the vortices is discussed.

Navier-Stokes solutions of unsteady separation induced by a vortex: Comparison with theory and influence of a moving wall

NASA Astrophysics Data System (ADS)

Obabko, Aleksandr Vladimirovich

Numerical solutions of the unsteady Navier-Stokes equations are considered for the flow induced by a thick-core vortex convecting along an infinite surface in a two-dimensional incompressible flow. The formulation is considered as a model problem of the dynamic-stall vortex and is relevant to other unsteady separation phenomena including vorticity ejections in juncture flows and the vorticity production mechanism in turbulent boundary-layers. Induced by an adverse streamwise pressure gradient due to the presence of the vortex above the wall, a primary recirculation region forms and evolves toward a singular solution of the unsteady non-interacting boundary-layer equations. The resulting eruptive spike provokes a small-scale viscous-inviscid interaction in the high-Reynolds-number regime. In the moderate-Reynolds-numbers regime, the growing recirculation region initiates a large-scale interaction in the form of local changes in the streamwise pressure gradient accelerating the spike formation and resulting small-scale interaction through development of a region of streamwise compression. It also was found to induce regions of streamwise expansion and "child" recirculation regions that contribute to ejections of near-wall vorticity and splitting of the "parent" region into multiple co-rotating eddies. These eddies later merge into a single amalgamated eddy that is observed to pair with the detaching vortex similar to the low-Reynolds-number regime where the large-scale interaction occurs, but there is no spike or subsequent small-scale interaction. It is also found that increasing the wall speed or vortex convection velocity toward a critical value results in solutions that are indicative of flows at lower Reynolds numbers eventually leading to suppression of unsteady separation and vortex detachment processes.

Control of unsteady separated flow associated with the dynamic pitching of airfoils

NASA Technical Reports Server (NTRS)

Ahmed, Sajeer

1991-01-01

Although studies have been done to understand the dependence of parameters for the occurrence of deep stall, studies to control the flow for sustaining lift for a longer time has been little. To sustain the lift for a longer time, an understanding of the development of the flow over the airfoil is essential. Studies at high speed are required to study how the flow behavior is dictated by the effects of compressibility. When the airfoil is pitched up in ramp motion or during the upstroke of an oscillatory cycle, the flow development on the upper surface of the airfoil and the formation of the vortex dictates the increase in lift behavior. Vortex shedding past the training edge decreases the lift. It is not clear what is the mechanism associated with the unsteady separation and vortex formation in present unsteady environment. To develop any flow control device, to suppress the vortex formation or delay separation, it is important that this mechanism be properly understood. The research activities directed toward understanding these questions are presented and the results are summarized.

Studies on ocular and parenteral application potentials of azithromycin- loaded anionic, cationic and neutral-charged emulsions.

PubMed

Tamilvanan, Shunmugaperumal; Khanum, Ramona; Senthilkumar, Sudalimuthu Ramachandran; Muthuraman, Marimuthu; Rajasekharan, Thenrajan

2013-10-01

Ocular and parenteral application potentials of azithromycin-containing, non-phospholipid-based cationic nanosized emulsion in comparison to the phospholipid-based anionic and neutral-charged nanosized emulsions were investigated. Various physical, chemical, nonclinical toxicity and antimicrobial activity studies (mean droplet diameter, surface charge, creaming index, entrapment efficiency, accelerated, long-term and freeze-thaw cycling stabilities, TLC study, modified hen's egg chorioallantoic membrane (HET-CAM) test, in vitro hemolysis test, in vitro and in vivo myotoxicity, and in vitro antimicrobial activity) were conducted for assessing the potentials of these three types of emulsions. Following autoclave sterilization, all of these emulsions exhibited a nanometer range mean particle diameter (200 ± 29 to 434 ± 13 nm). While the anionic and cationic emulsions did show high negative (-34.2 ± 1.23 mV) and positive zeta potential (42.6 ± 1.45 mV) values, the neutral-charged emulsion did not. Even with 5 freeze-thaw cycles, the cationic emulsion remained stable whereas other two emulsions underwent phase-separation. The hen's egg chorioallantoic membrane test revealed an irritation score value that was higher for the anionic emulsion than for cationic or neutral-charged emulsion. A significantly higher % hemolysis value was also noticed for the anionic emulsion when compared to the % hemolysis value of cationic emulsion (ANOVA, P ‹ 0.05). However, all of the emulsions showed a lesser intracellular creatine kinase (CK) release/plasma CK level in comparison to the positive control (phenytoin) indicating their lesser myotoxicity at the injection site . When compared to anionic and neutral-charged emulsions, the possible controlled drug release from cationic emulsion delayed the in vitro antimicrobial action against H.influenzae and S.pneumoniae.

An experimental study of pressures on 60 deg Delta wings with leading edge vortex flaps

NASA Technical Reports Server (NTRS)

Marchman, J. F., III; Terry, J. E.; Donatelli, D. A.

1983-01-01

An experimental study was conducted in the Virginia Tech Stability Wind Tunnel to determine surface pressures over a 60 deg sweep delta wing with three vortex flap designs. Extensive pressure data was collected to provide a base data set for comparison with computational design codes and to allow a better understanding of the flow over vortex flaps. The results indicated that vortex flaps can be designed which will contain the leading edge vortex with no spillage onto the wing upper surface. However, the tests also showed that flaps designed without accounting for flap thickness will not be optimum and the result can be oversized flaps, early flap vortex reattachment and a second separation and vortex at the wing/flap hinge line.

Recovery of Ni Metal from Spent Catalyst with Emulsion Liquid Membrane Using Cyanex 272 as Extractant

NASA Astrophysics Data System (ADS)

Yuliusman; Huda, M.; Ramadhan, I. T.; Farry, A. R.; Wulandari, P. T.; Alfia, R.

2018-03-01

In this study was conducted to recover nickel metal from spent nickel catalyst resulting from hydrotreating process in petroleum industry. The nickel extraction study with the emulsion liquid membrane using Cyanex 272 as an extractant to extract and separate nickel from the feed phase solution. Feed phase solution was preapred from spent catalyst using sulphuric acid. Liquid membrane consists of a kerosene as diluent, a Span 80 as surfactant, a Cyanex 272 as carrier and sulphuric acid solutions have been used as the stripping solution. The important parameters governing the permeation of nickel and their effect on the separation process have been studied. These parameters are surfactant concentration, extractant concentration feed phase pH. The optimum conditions of the emulsion membrane making process is using 0.06 M Cyanex 272, 8% w/v SPAN 80, 0.05 M H2SO4, internal phase extractant / phase volume ratio: 1/1, and stirring speed 1150 rpm for 60 Minute that can produce emulsion membrane with stability level above 90% after 4 hours. In the extraction process with optimum condition pH 6 for feed phase, ratio of phase emulsion/phase of feed: 1/2, and stirring speed 175 rpm for 15 minutes with result 81.51% nickel was extracted.

Vortex equations: Singularities, numerical solution, and axisymmetric vortex breakdown

NASA Technical Reports Server (NTRS)

Bossel, H. H.

1972-01-01

A method of weighted residuals for the computation of rotationally symmetric quasi-cylindrical viscous incompressible vortex flow is presented and used to compute a wide variety of vortex flows. The method approximates the axial velocity and circulation profiles by series of exponentials having (N + 1) and N free parameters, respectively. Formal integration results in a set of (2N + 1) ordinary differential equations for the free parameters. The governing equations are shown to have an infinite number of discrete singularities corresponding to critical values of the swirl parameters. The computations point to the controlling influence of the inner core flow on vortex behavior. They also confirm the existence of two particular critical swirl parameter values: one separates vortex flow which decays smoothly from vortex flow which eventually breaks down, and the second is the first singularity of the quasi-cylindrical system, at which point physical vortex breakdown is thought to occur.

Aircraft Vortex Wake Decay Near the Ground

DOT National Transportation Integrated Search

1977-05-01

A multi-faceted experimental and analytical research program was carried out to explore the details of aircraft wake vortex breakdown under conditions representative of those which prevail at low altitudes in the vicinity of airports. Three separate ...

Second harmonic generation of off axial vortex beam in the case of walk-off effect

NASA Astrophysics Data System (ADS)

Chen, Shunyi; Ding, Panfeng; Pu, Jixiong

2016-07-01

Process of off axial vortex beam propagating in negative uniaxial crystal is investigated in this work. Firstly, we get the formulae of the normalized electric field and calculate the location of vortices for second harmonic beam in two type of phase matching. Then, numerical analysis verifies that the intensity distribution and location of vortices of the first order original vortex beam depend on the walk-off angle and off axial magnitude. It is shown that, in type I phase matching, the distribution of vortices is symmetrical about the horizontal axis, the separation distance increases as the off axial magnitude increases or the off axial magnitude deceases. However, in type II phase matching, the vortices are symmetrical along with some vertical axis, and increase of the walk-off angle or off axial magnitude leads to larger separation distance. Finally, the case of high order original off axial vortex beam is also investigated.

Viscoelasticity of Depletion-Induced Emulsion Gels

NASA Astrophysics Data System (ADS)

Meller, Amit; Stavans, Joel; Gisler, Thomas; Weitz, David A.

1997-03-01

The presence of non-adsorbing polymer in an oil-in-water emulsion results in a depletion attraction between the emulsion droplets, causing a phase separation into an droplet-rich phase and a polymer-rich phase largely devoid of emulsion droplets. At high enough droplet concentration, however, this phase separation is kinetically arrested to a gel-like state where large (diameter>50 μm) clusters of droplets are weakly connected via ramifications, leading to a measurable elastic modulus. We measure the mean-square displacement <Δ r ^2 (t)> of a droplet of size a inside a cluster using diffusing wave spectroscopy (DWS); by means of a generalized Stokes-Einstein relation we obtain frequency dependent storage and loss moduli G'(ω) and G''(ω), respectively. G'(ω) reaches a plateau at frequencies between 1 rad/s and 100 rad/s; this plateau modulus is found to scale with the hard-sphere energy density k_BT/a^3; within the clusters the droplets are densely packed, yet remain undeformed, the droplet volume fraction being determined by the osmotic pressure exerted by the polymer.

Three-dimensional numerical investigation of the separation process in a vortex tube at different operating conditions

NASA Astrophysics Data System (ADS)

Rafiee, Seyed Ehsan; Sadeghiazad, M. M.

2016-06-01

Air separators provide safe, clean, and appropriate air flow to engines and are widely used in vehicles with large engines such as ships and submarines. In this operational study, the separation process inside a Ranque-Hilsch vortex tube cleaning (cooling) system is investigated to analyze the impact of the operating gas type on the vortex tube performance; the operating gases used are air, nitrogen, oxygen, carbon dioxide and nitrogen dioxide. The computational fluid dynamic model used is equipped with a three-dimensional structure, and the steady-state condition is applied during computations. The standard k-ɛ turbulence model is employed to resolve nonlinear flow equations, and various key parameters, such as hot and cold exhaust thermal drops, and power separation rates, are described numerically. The results show that nitrogen dioxide creates the greatest separation power out of all gases tested, and the numerical results are validated by good agreement with available experimental data. In addition, a comparison is made between the use of two different boundary conditions, the pressure-far-field and the pressure-outlet, when analyzing complex turbulent flows inside the air separators. Results present a comprehensive and practical solution for use in future numerical studies.

Vortex maneuver lift for super-cruise configurations

NASA Technical Reports Server (NTRS)

Campbell, J. F.; Gloss, B. B.; Lamar, J. E.

1976-01-01

Some of the theoretical and experimental research conducted at the NASA Langley Research Center is presented to investigate the subsonic vortex-lift producing capabilities for two classes of Super-Cruise designs: a close-coupled wing-canard arrangement and a slender wing configuration. In addition, several analytical methods are discussed for estimating critical structural design loads for thin, highly swept wings having separated leading-edge vortex flows.

Viscous and Interacting Flow Field Effects.

DTIC Science & Technology

1980-06-01

in the inviscid flow analysis using free vortex sheets whose shapes are determined by iteration. The outer iteration employs boundary layer...Methods, Inc. which replaces the source distribution in the separation zone by a vortex wake model . This model is described in some detail in (2), but...in the potential flow is obtained using linearly varying vortex singularities distributed on planar panels. The wake is represented by sheets of

Vortex Airy beams directly generated via liquid crystal q-Airy-plates

NASA Astrophysics Data System (ADS)

Wei, Bing-Yan; Liu, Sheng; Chen, Peng; Qi, Shu-Xia; Zhang, Yi; Hu, Wei; Lu, Yan-Qing; Zhao, Jian-Lin

2018-03-01

Liquid crystal q-Airy-plates with director distributions integrated by q-plates and polarization Airy masks are proposed and demonstrated via the photoalignment technique. Single/dual vortex Airy beams of opposite topological charges and orthogonal circular polarizations are directly generated with polarization-controllable characteristic. The singular phase of the vortex part is verified by both astigmatic transformation and digital holography. The trajectory of vortex Airy beams is investigated, manifesting separate propagation dynamics of optical vortices and Airy beams. Meanwhile, Airy beams still keep their intrinsic transverse acceleration, self-healing, and nondiffraction features. This work provides a versatile candidate for generating high-quality vortex Airy beams.

Review of the physics of enhancing vortex lift by unsteady excitation

NASA Technical Reports Server (NTRS)

Wu, J. Z.; Vakili, A. D.; Wu, J. M.

1991-01-01

A review aimed at providing a physical understanding of the crucial mechanisms for obtaining super lift by means of unsteady excitations is presented. Particular attention is given to physical problems, including rolled-up vortex layer instability and receptivity, wave-vortex interaction and resonance, nonlinear streaming, instability of vortices behind bluff bodies and their shedding, and vortex breakdown. A general theoretical framework suitable for handling the unsteady vortex flows is introduced. It is suggested that wings with swept and sharp leading edges, equipped with devices for unsteady excitations, could yield the first breakthrough of the unsteady separation barrier and provide super lift at post-stall angle of attack.

Vortex Ring Interaction With a Coaxially Aligned Cylinderical Rod

NASA Astrophysics Data System (ADS)

Arakeri, Jaywant H.; Rajmanoharan, P.; Koochesfahani, Manoochehr

1998-11-01

We present results of experiments of a fully developed vortex ring interacting with a cylinderical rod, having a rounded nose, placed coaxially in line with the motion of the ring. The pressure field of the translating ring causes unsteady boundary layer separation and results in the formation of one or more ( secondary ) vortex rings, that subsequently interact. The nature and strength of the interaction depends on the ratio of the cylinder diameter to the ring diameter. For the larger diameter cylinders the vortex ring travels a few ring diameters before it breaks up. For the smaller diameter cylinders the vortex ring speed decreases slowly and, simultaneously, its diameter increases.

Calculation of two dimensional vortex/surface interference using panel methods

NASA Technical Reports Server (NTRS)

Maskew, B.

1980-01-01

The application of panel methods to the calculation of vortex/surface interference characteristics in two dimensional flow was studied over a range of situations starting with the simple case of a vortex above a plane and proceeding to the case of vortex separation from a prescribed point on a thick section. Low order and high order panel methods were examined, but the main factor influencing the accuracy of the solution was the distance between control stations in relation to the height of the vortex above the surface. Improvements over the basic solutions were demonstrated using a technique based on subpanels and an applied doublet distribution.

Vortex-induced dynamic loads on a non-spinning volleyball

NASA Astrophysics Data System (ADS)

Qing-ding, Wei; Rong-sheng, Lin; Zhi-jie, Liu

1988-09-01

An experiment on vortex-induced dynamic loads on a non-spinning Volleyball was conducted in a wind tunnel. The flow past the Volleyball was visualized, and the aerodynamic load was measured by use of a strain gauge balance. The separation on the Volleyball was measured with hot-film. The experimental results suggest that under the action of an unstable tail vortex system the separation region is changeable, and that the fluctuation of drag and lateral forces is the same order of magnitude as the mean drag, no matter whether the seam of the Volleyball is symmetric or asymmetric, with regard to the flow. Based on the experimental data a numerical simulation of Volleyball swerve motion was made.

Generating and Separating Twisted Light by gradient-rotation Split-Ring Antenna Metasurfaces.

PubMed

Zeng, Jinwei; Li, Ling; Yang, Xiaodong; Gao, Jie

2016-05-11

Nanoscale compact optical vortex generators promise substantially significant prospects in modern optics and photonics, leading to many advances in sensing, imaging, quantum communication, and optical manipulation. However, conventional vortex generators often suffer from bulky size, low vortex mode purity in the converted beam, or limited operation bandwidth. Here, we design and demonstrate gradient-rotation split-ring antenna metasurfaces as unique spin-to-orbital angular momentum beam converters to simultaneously generate and separate pure optical vortices in a broad wavelength range. Our proposed design has the potential for realizing miniaturized on-chip OAM-multiplexers, as well as enabling new types of metasurface devices for the manipulation of complex structured light beams.

Preparation of hybrid thiol-acrylate emulsion-templated porous polymers by interfacial copolymerization of high internal phase emulsions.

PubMed

Langford, Caitlin R; Johnson, David W; Cameron, Neil R

2015-05-01

Emulsion-templated highly porous polymers (polyHIPEs), containing distinct regions differing in composition, morphology, and/or properties, are prepared by the simultaneous polymerization of two high internal phase emulsions (HIPEs) contained within the same mould. The HIPEs are placed together in the mould and subjected to thiol-acrylate photopolymerization. The resulting polyHIPE material is found to contain two distinct semicircular regions, reflecting the composition of each HIPE. The original interface between the two emulsions becomes a copolymerized band between 100 and 300 μm wide, which is found to be mechanically robust. The separate polyHIPE layers are distinguished from one another by their differing average void diameter, chemical composition, and extent of contraction upon drying. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Heteroaggregation of lipid droplets coated with sodium caseinate and lactoferrin.

PubMed

de Figueiredo Furtado, Guilherme; Michelon, Mariano; de Oliveira, Davi Rocha Bernardes; da Cunha, Rosiane Lopes

2016-11-01

Formation and characterization of droplet heteroaggregates were investigated by mixing two emulsions previously stabilized by proteins oppositely charged. Emulsions were composed of 5vol.% of sunflower oil and 95vol.% of sodium caseinate or lactoferrin aqueous dispersions. They were produced using ultrasound with fixed power (300W) and sonication time (6min). Different volume ratios (0-100%) of sodium caseinate-stabilized emulsion (droplet diameter around 1.75μm) to lactoferrin-stabilized emulsion (droplet diameter around 1.55μm) were mixed under conditions that both proteins showed opposite charges (pH7). Influence of ionic strength (0-400mM NaCl) on the heteroaggregates stability was also evaluated. Creaming stability, zeta potential, microstructure, mean particle diameter and rheological properties of the heteroaggregates were measured. These properties depended on the volume ratio (0-100%) of sodium caseinate to lactoferrin-stabilized emulsion (C:L) and the ionic strength. In the absence of salt, different zeta potential values were obtained, rheological properties (viscosity and elastic moduli) were improved and the largest heteroaggregates were formed at higher content of lactoferrin-stabilized emulsion (60-80%). The system containing 40 and 60vol.% of sodium caseinate and lactoferrin stabilized emulsion, respectively, presented good stability against phase separation besides showing enhanced rheological and size properties due to extensive droplets aggregation. Phase separation was observed only in the absence of sodium caseinate, demonstrating the higher susceptibility of lactoferrin to NaCl. The heteroaggregates produced may be useful functional agents for texture modification and controlled release since different rheological properties and sizes can be achieved depending on protein concentrations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Feasibility of Freeze-Drying Oil-in-Water Emulsion Adjuvants and Subunit Proteins to Enable Single-Vial Vaccine Drug Products.

PubMed

Iyer, Vidyashankara; Cayatte, Corinne; Marshall, Jason D; Sun, Jenny; Schneider-Ohrum, Kirsten; Maynard, Sean K; Rajani, Gaurav Manohar; Bennett, Angie Snell; Remmele, Richard L; Bishop, Steve M; McCarthy, Michael P; Muralidhara, Bilikallahalli K

2017-06-01

To generate potent vaccine responses, subunit protein antigens typically require coformulation with an adjuvant. Oil-in-water emulsions are among the most widely investigated adjuvants, based on their demonstrated ability to elicit robust antibody and cellular immune responses in the clinic. However, most emulsions cannot be readily frozen or lyophilized, on account of the risk of phase separation, and may have a deleterious effect on protein antigen stability when stored long term as a liquid coformulation. To circumvent this, current emulsion-formulated vaccines generally require a complex multivial presentation with obvious drawbacks, making a single-vial presentation for such products highly desirable. We describe the development of a stable, lyophilized squalene emulsion adjuvant through innovative formulation and process development approaches. On reconstitution, freeze-dried emulsion preparations were found to have a minimal increase in particle size of ∼20 nm and conferred immunogenicity in BALB/c mice similar in potency to freshly prepared emulsion coformulations in liquid form. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Coencapsulation of (-)-Epigallocatechin-3-gallate and Quercetin in Particle-Stabilized W/O/W Emulsion Gels: Controlled Release and Bioaccessibility.

PubMed

Chen, Xing; McClements, David Julian; Wang, Jian; Zou, Liqiang; Deng, Sumeng; Liu, Wei; Yan, Chi; Zhu, Yuqing; Cheng, Ce; Liu, Chengmei

2018-04-11

Particle-stabilized W 1 /O/W 2 emulsion gels were fabricated using a two-step procedure: ( i) a W 1 /O emulsion was formed containing saccharose (for osmotic stress balance) and gelatin (as a gelling agent) in the aqueous phase and polyglycerol polyricinoleate (a lipophilic surfactant) in the oil phase; ( ii) this W 1 /O emulsion was then homogenized with another water phase (W 2 ) containing wheat gliadin nanoparticles (hydrophilic emulsifier). The gliadin nanoparticles in the external aqueous phase aggregated at pH 5.5, which led to the formation of particle-stabilized W 1 /O/W 2 emulsion gels with good stability to phase separation. These emulsion gels were then used to coencapsulate a hydrophilic bioactive (epigallocatechin-3-gallate, EGCG) in the internal aqueous phase (encapsulation efficiency = 65.5%) and a hydrophobic bioactive (quercetin) in the oil phase (encapsulation efficiency = 97.2%). The emulsion gels improved EGCG chemical stability and quercetin solubility under simulated gastrointestinal conditions, which led to a 2- and 4-fold increase in their effective bioaccessibility, respectively.

Thermodynamic compatibility and interactions between Speckled Sugar bean protein and xanthan gum for production of multilayer O/W emulsion.

PubMed

Rahmati, Nazanin Fatemeh; Koocheki, Arash; Varidi, Mehdi; Kadkhodaee, Rassoul

2018-03-01

Thermodynamic compatibility and probable interactions between Speckled Sugar been protein (SSBP) and xanthan gum for production of multilayer O/W emulsion (30% oil) were investigated. Different interactions were observed between SSBP and xanthan at different pH (3-7) including electrostatic interactions and hydrogen bonding. These interactions were predominant at pH 3. When low xanthan gum concentration (0.1%) was used, phase separation and complex coacervation observed at this pH (negative effect of interactions). However, at pH 5, only 0.1% xanthan was enough to drastically reduce non-dissolved protein and its precipitation which normally occurs at this pH. In addition, incompatibility or segregative phase behavior which normally occurs when protein and polysaccharide have same charges was not observed (positive effects of interactions). Protein-gum interactions influenced emulsion properties (zeta potential, particle size, PDI, rheology, emulsion capacity, heat stability and creaming rate). Interactions had considerable influence on emulsion shelf life and produced completely stable emulsions at all pH values. Results confirmed that SSBP-xanthan gum mixture has a high potential for production of multilayer emulsions.

Demulsification of crude oil-in-water emulsions by means of fungal spores.

PubMed

Vallejo-Cardona, Alba Adriana; Martínez-Palou, Rafael; Chávez-Gómez, Benjamín; García-Caloca, Graciela; Guerra-Camacho, Jairo; Cerón-Camacho, Ricardo; Reyes-Ávila, Jesús; Karamath, James Robert; Aburto, Jorge

2017-01-01

The present feature describes for the first time the application of spores from Aspergillus sp. IMPMS7 to break out crude oil-in-water emulsions (O/W). The fungal spores were isolated from marine sediments polluted with petroleum hydrocarbons. The spores exhibited the ability to destabilize different O/W emulsions prepared with medium, heavy or extra-heavy Mexican crude oils with specific gravities between 10.1 and 21.2°API. The isolated fungal spores showed a high hydrophobic power of 89.3 ± 1.9% and with 2 g of spores per liter of emulsion, the half-life for emulsion destabilization was roughly 3.5 and 0.7 h for extra-heavy and medium crude oil, respectively. Then, the kinetics of water separation and the breaking of the O/W emulsion prepared with heavy oil through a spectrofluorometric technique were studied. A decrease in the fluorescence ratio at 339 and 326 nm (I339/I326) was observed in emulsions treated with spores, which is similar to previously reported results using chemical demulsifiers.

Demulsification of crude oil-in-water emulsions by means of fungal spores

PubMed Central

Vallejo-Cardona, Alba Adriana; Martínez-Palou, Rafael; Chávez-Gómez, Benjamín; García-Caloca, Graciela; Guerra-Camacho, Jairo; Cerón-Camacho, Ricardo; Reyes-Ávila, Jesús; Karamath, James Robert

2017-01-01

The present feature describes for the first time the application of spores from Aspergillus sp. IMPMS7 to break out crude oil-in-water emulsions (O/W). The fungal spores were isolated from marine sediments polluted with petroleum hydrocarbons. The spores exhibited the ability to destabilize different O/W emulsions prepared with medium, heavy or extra-heavy Mexican crude oils with specific gravities between 10.1 and 21.2°API. The isolated fungal spores showed a high hydrophobic power of 89.3 ± 1.9% and with 2 g of spores per liter of emulsion, the half-life for emulsion destabilization was roughly 3.5 and 0.7 h for extra-heavy and medium crude oil, respectively. Then, the kinetics of water separation and the breaking of the O/W emulsion prepared with heavy oil through a spectrofluorometric technique were studied. A decrease in the fluorescence ratio at 339 and 326 nm (I339/I326) was observed in emulsions treated with spores, which is similar to previously reported results using chemical demulsifiers. PMID:28234917

Conference on Capacity and Wake Vortices Held in Imperial College of Science, London on 11-14 September 2001. Abstracts of Presentations

NASA Technical Reports Server (NTRS)

Whitelaw, J. H.

2001-01-01

Partial Contents: The Effect of Aircraft Wake Vortex Separation on Air Transportation Capacity; The Pilots View of Wake Vortices - Capacity vs. Safety; Runway Capacity Constraints at Heathrow Airport; FAA's Research Strategy; Increasing Capacity by Wake Turbulence Avoidance Systems at Frankfurt/Main Airport; Improving Airport Capacity Using Vertical Flight; Recent Developments in Industrial Wake Vortex Research; Vortex Evolution and Characterization; PIV -Survey of the Vortex Wake Structure behind an Airbus A340 in a Towing Tank.

Rejuvenation of Spent Media via Supported Emulsion Liquid Membranes

NASA Technical Reports Server (NTRS)

Wiencek, John M.

2002-01-01

The overall goal of this project is to maximize the reuseability of spent fermentation media. Supported emulsion liquid membrane separation, a highly efficient extraction technique, is used to remove inhibitory byproducts during fermentation; thus, improving the yield while reducing the need for fresh water. The key objectives of this study are: Develop an emulsion liquid membrane system targeting low molecular weight organic acids which has minimal toxicity on a variety of microbial systems; Conduct mass transfer studies to allow proper modeling and design of a supported emulsion liquid membrane system; Investigate the effect of gravity on emulsion coalescence within the membrane unit; Access the effect of water re-use on fermentation yields in a model microbial system; Develop a perfusion-type fermentor utilizing a supported emulsion liquid membrane system to control inhibitory fermentation byproducts; Work for the coming year will focus on the determination of toxicity of various solvents, selection of the emulsifying agents, as well as characterizing the mass transfer of hollow-fiber contactors.

Interfacial film stabilized W/O/W nano multiple emulsions loaded with green tea and lotus extracts: systematic characterization of physicochemical properties and shelf-storage stability.

PubMed

Mahmood, Tariq; Akhtar, Naveed; Manickam, Sivakumar

2014-05-12

Multiple emulsions have excellent encapsulating potential and this investigation has been aimed to encapsulate two different plant extracts as functional cosmetic agents in the W/O/W multiple emulsions and the resultant system's long term stability has been determined in the presence of a thickener, hydroxypropyl methylcellulose (HPMC). Multiple W/O/W emulsions have been generated using cetyl dimethicone copolyol as lipophilic emulsifier and a blend of polyoxyethylene (20) cetyl ether and cetomacrogol 1000® as hydrophilic emulsifiers. The generated multiple emulsions have been characterized with conductivity, pH, microscopic analysis, phase separation and rheology for a period of 30 days. Moreover, long term shelf-storage stability has been tested to understand the shelf-life by keeping the generated multiple emulsion formulations at 25 ± 10°C and at 40 ± 10% relative humidity for a period of 12 months. It has been observed that the hydrophilic emulsifiers and HPMC have considerably improved the stability of multiple emulsions for the followed period of 12 months at different storage conditions. These multiple emulsions have shown improved entrapment efficiencies concluded on the release rate of conductometric tracer entrapped in the inner aqueous phase of the multiple emulsions. Multiple emulsions have been found to be stable for a longer period of time with promising characteristics. Hence, stable multiple emulsions loaded with green tea and lotus extracts could be explored for their cosmetic benefits.

Zero liquid carryover whole-body shower vortex liquid/gas separator

NASA Technical Reports Server (NTRS)

1975-01-01

The development and evaluation of a liquid/gas vortex type separator design eliminating liquid and semi-liquid (suds) carryover into air recirculating system were described. Consideration was given to a number of soaps other than the "Miranol JEM" which was the low sudsing soap used in previous test runs of the space shower. Analysis of test parameters and prototype testing resulted in a revised separator configuration and a better understanding of the suds generating mechanism in the wastewater collection system. The final design of the new separator provides for a wider choice of soaps without leading to the problem of "carryover". Furthermore, no changes in separator-to-shower interfaces were required. The new separator was retrofitted on the "space shower" and satisfactorily demonstrated in one-g testing.

Unsteady Separated Flows: Vorticity and Turbulence.

DTIC Science & Technology

1982-10-01

investigation. The vortex train used in the mathe- matical model is adapted to simulate the flow generated in the wake of an oscillating spoiler moving...weak wake structure. C H - At K = 1.5, the trailing edge vortex clearly leads the vorte : generated from the leading edge in the normal geonetry tests...flows is summarized. Specific projects reviewed include: (a) oscillating airfoil dynamic stall; (b) vortex entrapment and stability analysis -and (c

Modelling of Time-Variant Flows Using Vortex Dynamics.

DTIC Science & Technology

1987-02-01

eopennage.... ) avec nappes enroul~es et d~ chir ~cs. REFERENCES Ji .T. BEALE, A. MAJDA "Nigh order accurate vortex methods with explicit velocity kernel...discrete vortices. Two papers, Longuet- Higgins (37) and Smith and Stansby (38) deal with the problem. In (37) conformal transformation is used for the...Longuet- Higgins (37). Most experiments on separated flows undoubtedly contain three-dimensional effects and again vortex decay is occasionally put into the

A Hybrid Vortex Sheet / Point Vortex Model for Unsteady Separated Flows

NASA Astrophysics Data System (ADS)

Darakananda, Darwin; Eldredge, Jeff D.; Colonius, Tim; Williams, David R.

2015-11-01

The control of separated flow over an airfoil is essential for obtaining lift enhancement, drag reduction, and the overall ability to perform high agility maneuvers. In order to develop reliable flight control systems capable of realizing agile maneuvers, we need a low-order aerodynamics model that can accurately predict the force response of an airfoil to arbitrary disturbances and/or actuation. In the present work, we integrate vortex sheets and variable strength point vortices into a method that is able to capture the formation of coherent vortex structures while remaining computationally tractable for control purposes. The role of the vortex sheet is limited to tracking the dynamics of the shear layer immediately behind the airfoil. When parts of the sheet develop into large scale structures, those sections are replaced by variable strength point vortices. We prevent the vortex sheets from growing indefinitely by truncating the tips of the sheets and transfering their circulation into nearby point vortices whenever the length of sheet exceeds a threshold. We demonstrate the model on a variety of canonical problems, including pitch-up and impulse translation of an airfoil at various angles of attack. Support by the U.S. Air Force Office of Scientific Research (FA9550-14-1-0328) with program manager Dr. Douglas Smith is gratefully acknowledged.

Structural micro-porous carbon anode for rechargeable lithium-ion batteries

DOEpatents

Delnick, Frank M.; Even, Jr., William R.; Sylwester, Alan P.; Wang, James C. F.; Zifer, Thomas

1995-01-01

A secondary battery having a rechargeable lithium-containing anode, a cathode and a separator positioned between the cathode and anode with an organic electrolyte solution absorbed therein is provided. The anode comprises three-dimensional microporous carbon structures synthesized from polymeric high internal phase emulsions or materials derived from this emulsion source, i.e., granules, powders, etc.

Fuel injection of coal slurry using vortex nozzles and valves

DOEpatents

Holmes, Allen B.

1989-01-01

Injection of atomized coal slurry fuel into an engine combustion chamber is achieved at relatively low pressures by means of a vortex swirl nozzle. The outlet opening of the vortex nozzle is considerably larger than conventional nozzle outlets, thereby eliminating major sources of failure due to clogging by contaminants in the fuel. Control fluid, such as air, may be used to impart vorticity to the slurry and/or purge the nozzle of contaminants during the times between measured slurry charges. The measured slurry charges may be produced by a diaphragm pump or by vortex valves controlled by a separate control fluid. Fluidic circuitry, employing vortex valves to alternatively block and pass cool slurry fuel flow, is disclosed.

Geostrophic tripolar vortices in a two-layer fluid: Linear stability and nonlinear evolution of equilibria

NASA Astrophysics Data System (ADS)

Reinaud, J. N.; Sokolovskiy, M. A.; Carton, X.

2017-03-01

We investigate equilibrium solutions for tripolar vortices in a two-layer quasi-geostrophic flow. Two of the vortices are like-signed and lie in one layer. An opposite-signed vortex lies in the other layer. The families of equilibria can be spanned by the distance (called separation) between the two like-signed vortices. Two equilibrium configurations are possible when the opposite-signed vortex lies between the two other vortices. In the first configuration (called ordinary roundabout), the opposite signed vortex is equidistant to the two other vortices. In the second configuration (eccentric roundabouts), the distances are unequal. We determine the equilibria numerically and describe their characteristics for various internal deformation radii. The two branches of equilibria can co-exist and intersect for small deformation radii. Then, the eccentric roundabouts are stable while unstable ordinary roundabouts can be found. Indeed, ordinary roundabouts exist at smaller separations than eccentric roundabouts do, thus inducing stronger vortex interactions. However, for larger deformation radii, eccentric roundabouts can also be unstable. Then, the two branches of equilibria do not cross. The branch of eccentric roundabouts only exists for large separations. Near the end of the branch of eccentric roundabouts (at the smallest separation), one of the like-signed vortices exhibits a sharp inner corner where instabilities can be triggered. Finally, we investigate the nonlinear evolution of a few selected cases of tripoles.

Numerical Study of Wake Vortex Interaction with the Ground Using the Terminal Area Simulation System

NASA Technical Reports Server (NTRS)

Proctor, Fred H.; Han, Jongil

1999-01-01

A sensitivity study for the in-ground effect on aircraft wake vortices has been conducted using a validated large eddy simulation model. The numerical results are compared with observed data and show good agreement for vortex decay and lateral vortex transport. The vortex decay rate is strongly influenced by the ground, but appears somewhat insensitive to ambient turbulence. In addition, the results show that the ground can affect the trajectory and descent-rate of a wake vortex pair at elevations up to about 3 b(sub o) (where b(sub o) is the initial vortex separation). However, the ground does not influence the average circulation of the vortices until the cores descend to within about 0.6 b(sub o), after which time the ground greatly enhances their rate of demise. Vortex rebound occurs in the simulations, but is more subtle than shown in previous numerical studies.

A study of the stabilities, microstructures and fuel characteristics of tri-fuel (diesel-biodiesel-ethanol) using various fuel preparation methods

NASA Astrophysics Data System (ADS)

Lee, K. H.; Mukhtar, N. A. M.; Yohaness Hagos, Ftwi; Noor, M. M.

2017-10-01

In this study, the work was carried out to investigate the effects of ethanol proportions on the stabilities and physicochemical characteristics of tri-fuel (Diesel-Biodiesel-Ethanol). For the first time, tri-fuel emulsions and blended were compared side by side. The experiment was done with composition having 5%, 10%, 15%, 20% and 25 % of ethanol with fixed 10% of biodiesel from palm oil origin on a volume basis into diesel. The results indicated that the phase stabilities of the emulsified fuels were higher compared to the blended fuels. In addition, tri-fuel composition with higher proportion of ethanol were found unstable with high tendency to form layer separation. It was found that tri-fuel emulsion with 5% ethanol content (D85B10E5) was of the best in stability with little separation. Furthermore, tri-fuel with lowest ethanol proportion indicated convincing physicochemical characteristics compared to others. Physicochemical characteristics of tri-fuel blending yield almost similar results to tri-fuel emulsion but degrading as more proportion ethanol content added. Emulsion category had cloudy look but on temporarily basis. Under the microscope, tri-fuel emulsion and blending droplet were similar for its active moving about micro-bubble but distinct in term of detection of collision, average disperse micro-bubble size, the spread and organization of the microstructure.

BKT phase transition in a 2D system with long-range dipole-dipole interaction

NASA Astrophysics Data System (ADS)

Fedichev, P. O.; Men'shikov, L. I.

2012-01-01

We consider phase transitions in 2D XY-like systems with long-range dipole-dipole interactions and demonstrate that BKT-type phase transition always occurs separating the ordered (ferroelectric) and the disordered (paraelectric) phases. The low-temperature phase corresponds to a thermal state with bound vortex-antivortex pairs characterized by linear attraction at large distances. Using the Maier-Schwabl topological charge model, we show that bound vortex pairs polarize and screen the vortex-antivortex interaction, leaving only the logarithmic attraction at sufficiently large separations between the vortices. At higher temperatures the pairs dissociate and the phase transition similar to BKT occurs, though at a larger temperature than in a system without the dipole-dipole interaction.

Laminar Horse Shoe Vortex for a Triangular Cylinder Flat Plate Juncture

NASA Astrophysics Data System (ADS)

Younis, Muhammad Yamin; Zhang, H.; Hu, B.; Sohail, Muhammad Amjad; Muhammad, Zaka

2011-09-01

Juncture Flows are 3-D flows which occur when fluid, flowing on a flat surface encounters an obstacle on its way. The flow separates from the surface due to the adverse pressure gradient produced by the obstacle and rolls up to form a vortical structure known as "Horse Shoe Vortex". Studies and research is underway to completely identify and understand different hidden features of the horse shoe vortex. In the present study the structure of horse shoe vortex for a Triangular cylinder flat plate juncture is visualized using particle image velocimetry (PIV). The diameter Reynolds number experimented is within the range of 2 000 ≤ ReA ≤ 8 000. The flow characteristics are studied for the horse shoe vortex and the flow is categorized into different flow regimes. (1) Steady or static vortex system, (2) periodic amalgamating vortex system, and (3) periodic break away vortex system. The range for different vortex systems is also calculated with shedding frequency for the periodic unsteady vortex system. Most importantly the range of Reynolds number for which the above mentioned vortex systems exist is much higher for Sharp leading edge cylinder than for blunt (circular and Elliptical) and flat (Square) leading edge cylinders studied earlier.

Biomimetic super-lyophobic and super-lyophilic materials applied for oil/water separation: a new strategy beyond nature.

PubMed

Wang, Ben; Liang, Weixin; Guo, Zhiguang; Liu, Weimin

2015-01-07

Oil spills and industrial organic pollutants have induced severe water pollution and threatened every species in the ecological system. To deal with oily water, special wettability stimulated materials have been developed over the past decade to separate oil-and-water mixtures. Basically, synergy between the surface chemical composition and surface topography are commonly known as the key factors to realize the opposite wettability to oils and water and dominate the selective wetting or absorption of oils/water. In this review, we mainly focus on the development of materials with either super-lyophobicity or super-lyophilicity properties in oil/water separation applications where they can be classified into four kinds as follows (in terms of the surface wettability of water and oils): (i) superhydrophobic and superoleophilic materials, (ii) superhydrophilic and under water superoleophobic materials, (iii) superhydrophilic and superoleophobic materials, and (iv) smart oil/water separation materials with switchable wettability. These materials have already been applied to the separation of oil-and-water mixtures: from simple oil/water layered mixtures to oil/water emulsions (including oil-in-water emulsions and water-in-oil emulsions), and from non-intelligent materials to intelligent materials. Moreover, they also exhibit high absorption capacity or separation efficiency and selectivity, simple and fast separation/absorption ability, excellent recyclability, economical efficiency and outstanding durability under harsh conditions. Then, related theories are proposed to understand the physical mechanisms that occur during the oil/water separation process. Finally, some challenges and promising breakthroughs in this field are also discussed. It is expected that special wettability stimulated oil/water separation materials can achieve industrial scale production and be put into use for oil spills and industrial oily wastewater treatment in the near future.

Manipulation of upstream rotor leading edge vortex and its effects on counter rotating propeller noise

NASA Technical Reports Server (NTRS)

Squires, Becky

1993-01-01

The leading edge vortex of a counter rotating propeller (CRP) model was altered by using shrouds and by turning the upstream rotors to a forward sweep configuration. Performance, flow, and acoustic data were used to determine the effect of vortex impingement on the noise signature of the CRP system. Forward sweep was found to eliminate the leading edge vortex of the upstream blades. Removal of the vortex had little effect on the tone noise at the forward and rear blade passing frequencies (BPF's) but significantly altered both the sound pressure level and directivity of the interaction tone which occurs at the sum of the two BPF's. A separate manipulation of the leading edge vortex performed by installing shrouds of various inlet length on the CRP verified that diverting the vortex path increases the noise level of the interaction tone. An unexpected link has been established between the interaction tone and the leading edge vortex-blade interaction phenomenon.

Flow visualization study of a vortex-wing interaction

NASA Technical Reports Server (NTRS)

Mehta, R. D.; Lim, T. T.

1984-01-01

A flow visualization study in water was completed on the interaction of a streamwise vortex with a laminar boundary layer on a two-dimensional wing. The vortex was generated at the tip of a finite wing at incidence, mounted perpendicular to the main wing, and having the same chord as the main wing. The Reynolds number based on wing chord was about 5000. Two different visualization techniques were used. One involved the injection of two different colored dyes into the vortex and the boundary layer. The other technique utilized hydrogen bubbles as an indicator. The position of the vortex was varied in a directional normal to the wing. The angle of attack of the main wing was varied from -5 to +12.5 deg. The vortex induced noticeable cross flows in the wing boundary layer from a distance equivalent to 0.75 chords. When very close to the wing, the vortex entrained boundary layer fluid and caused a cross flow separation which resulted in a secondary vortex.

Photogrammetric technique for in-flight ranging of trailing vortices using entrained balloons

NASA Technical Reports Server (NTRS)

Snow, Walter L.; Burner, Alpheus W.; Goad, William K.

1989-01-01

A method for experimentally determining the radial distance of a probe aircraft from a trailing vortex is described. The method relies on photogrammetric triangulation of targets entrained in the vortex core. The theory and preliminary testing were described using laboratory mock-ups. Solid state video cameras were to provide data at 300 Hz rates. Practical methods for seeding the vortex are under separate investigation and are not addressed.

Effects of Double-Leakage Tip Clearance Flow on the Performance of a Compressor Stage with a Large Rotor Tip Gap

NASA Technical Reports Server (NTRS)

Hah, Chunill

2016-01-01

Effects of a large rotor tip gap on the performance of a one and half stage axial compressor are investigated in detail with a numerical simulation based on LES and available PIV data. The current paper studies the main flow physics, including why and how the loss generation is increased with the large rotor tip gap. The present study reveals that when the tip gap becomes large, tip clearance fluid goes over the tip clearance core vortex and enters into the next blade's tip gap, which is called double-leakage tip clearance flow. As the tip clearance flow enters into the adjacent blade's tip gap, a vortex rope with a lower pressure core is generated. This vortex rope breaks up the tip clearance core vortex of the adjacent blade, resulting in a large additional mixing. This double-leakage tip clearance flow occurs at all operating conditions, from design flow to near stall condition, with the large tip gap for the current compressor stage. The double-leakage tip clearance flow, its interaction with the tip clearance core vortex of the adjacent blade, and the resulting large mixing loss are the main flow mechanism of the large rotor tip gap in the compressor. When the tip clearance is smaller, flow near the end wall follows more closely with the main passage flow and this double-leakage tip clearance flow does not happen near the design flow condition for the current compressor stage. When the compressor with a large tip gap operates at near stall operation, a strong vortex rope is generated near the leading edge due to the double-leakage flow. Part of this vortex separates from the path of the tip clearance core vortex and travels from the suction side of the blade toward the pressure side of the blade. This vortex is generated periodically at near stall operation with a large tip gap. As the vortex travels from the suction side to the pressure side of the blade, a large fluctuation of local pressure forces blade vibration. Nonsynchronous blade vibration occurs due to this vortex as the frequency of this vortex generation is not the same as the rotor. The present investigation confirms that this vortex is a part of separated tip clearance vortex, which is caused by the double-leakage tip clearance flow.

Vortical flow management techniques

NASA Technical Reports Server (NTRS)

Rao, Dhanvada M.; Campbell, James F.

1987-01-01

The aerodynamic performance and controllability of advanced, highly maneuverable supersonic aircraft can be enhanced by means of 'vortex management', which refers to the purposeful manipulation and reordering of stable and concentrated vortical structures due to flow separations from highly swept leading edges and slender forebodies at moderate-to-high angles-of-attack. Attention is presently given to a variety of results obtained in the course of experiments on generic research models at NASA Langley, clarifying their underlying aerodynamics and evaluating their performance-improvement potential. The vortex-management concepts discussed encompass aerodynamic compartmentation of highly swept leading edges, vortex lift augmentation and modulation, and forebody vortex manipulation.

Visualizing Pure Quantum Turbulence in Superfluid 3He: Andreev Reflection and its Spectral Properties.

PubMed

Baggaley, A W; Tsepelin, V; Barenghi, C F; Fisher, S N; Pickett, G R; Sergeev, Y A; Suramlishvili, N

2015-07-03

Superfluid 3He-B in the zero-temperature limit offers a unique means of studying quantum turbulence by the Andreev reflection of quasiparticle excitations by the vortex flow fields. We validate the experimental visualization of turbulence in 3He-B by showing the relation between the vortex-line density and the Andreev reflectance of the vortex tangle in the first simulations of the Andreev reflectance by a realistic 3D vortex tangle, and comparing the results with the first experimental measurements able to probe quantum turbulence on length scales smaller than the intervortex separation.

Pickering emulsion stabilized by cashew gum- poly-l-lactide copolymer nanoparticles: Synthesis, characterization and amphotericin B encapsulation.

PubMed

Richter, A R; Feitosa, J P A; Paula, H C B; Goycoolea, F M; de Paula, R C M

2018-04-01

In this work, we provide proof-of-concept of formation, physical characteristics and potential use as a drug delivery formulation of Pickering emulsions (PE) obtained by a novel method that combines nanoprecipitation with subsequent spontaneous emulsification process. To this end, pre-formed ultra-small (d.∼10 nm) nanoprecipitated nanoparticles of hydrophobic derivatives of cashew tree gum grafted with polylactide (CGPLAP), were conceived to stabilize Pickering emulsions obtained by spontaneous emulsification. These were also loaded with Amphotericin B (AmB), a drug of low oral bioavailability used in the therapy of neglected diseases such as leishmaniasis. The graft reaction was performed in two CG/PLA molar ratio conditions (1:1 and 1:10). Emulsions were prepared by adding the organic phase (Miglyol 812 ® ) in the aqueous phase (nanoprecipitated CGPLAP), resulting the immediate emulsion formation. The isolation by centrifugation does not destabilize or separate the nanoparticles from oil droplets of the PE emulsion. Emulsions with CGPLAP 1:1 presented unimodal distributions at different CGPLA concentration, lower values in size and PDI and the best stability over time. The AmB was incorporated in the emulsions with a process efficiency of 21-47%, as determined by UV-vis. AmB in CGPLAP emulsions is in less aggregated state than observed in commercial AmB formulation. Copyright © 2018 Elsevier B.V. All rights reserved.

BACLOFEN, RACLOPRIDE, AND NALTREXONE DIFFERENTIALLY REDUCE SOLID FAT EMULSION INTAKE UNDER LIMITED ACCESS CONDITIONS

PubMed Central

RE, Rao; FHE, Wojnicki; J, Coupland; S, Ghosh; RLW, Corwin

2009-01-01

Previous work in rats has demonstrated that an Intermittent (Monday, Wednesday, Friday) schedule of access promotes binge-type consumption of 100% vegetable shortening during a 1-hour period of availability. The present study used novel shortening-derived stable solid emulsions of various fat concentrations. These emulsions were the consistency of pudding and did not demonstrate oil and water phase separation previously reported with oil-based liquid emulsions. Male Sprague-Dawley rats were grouped according to schedule of access (Daily or Intermittent) to one of three concentrations (18%, 32%, 56%) of solid fat emulsion. There were no significant Intermittent vs. Daily differences in amount consumed, due to high intakes in all groups. This indicated the acceptability of the emulsions. Baclofen (GABA-B agonist) and raclopride (D2-like antagonist) both significantly reduced emulsion intake in all Daily groups, but only in the 56% fat Intermittent group. Naltrexone (opioid antagonist), in contrast, significantly reduced 32% and 56% fat emulsion intake in the Intermittent, as well as the Daily groups. These results indicate that the fat intake reducing effects of GABAB activation and D2 blockade depend upon fat concentration and schedule of fat access, while the fat intake reducing effects of opioid blockade depend upon fat concentration but not schedule of access. PMID:18353432

Electrical process in the breaking of dilute oil-in-water emulsions. Completion report, 1 July 1973-30 June 1974

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orr, C. Jr.; Keng, E.Y.H.

1974-06-01

Oils, greases, and waxes frequently occur in industrial waste waters. Simultaneously, soaps and detergents enter most waste waters from domestic and other sources. When the mixtures of waste particles in water, known as emulsions, come in contact with the soaps and detergents, they generally become quite stable. One way to break such emulsions and thereby separate out the wastes is to add chemicals that will cause the oil droplet to agglomerate into larger drops. This study sought to assess the usefulness of electrical measurements, particularly the so-called zeta potential, in guiding the treatment process to chemicals and application rates thatmore » can break measured emulsions. When the zeta potential, which for a highly stable emulsion may be as negative as -0.090 volt, is made to approach -0.015 volt, the stability of the emulsion deteriorates rapidly. Past this poin oil-in-water emulsions often break spontaneously. The larger drops will then rise to the water surface and form a distinct oil layer that can be easily removed. Laboratory applications of various chemicals to emulsion samples and subsequent zeta potential measurement should thus provide a ready guide to those trying to remove oily waste water discharge.« less

Biomimetic Multilayer Nanofibrous Membranes with Elaborated Superwettability for Effective Purification of Emulsified Oily Wastewater.

PubMed

Ge, Jianlong; Jin, Qing; Zong, Dingding; Yu, Jianyong; Ding, Bin

2018-05-09

Creating a porous membrane to effectively separate the emulsified oil-in-water emulsions with energy-saving property is highly desired but remains a challenge. Herein, a multilayer nanofibrous membrane was developed with the inspiration of the natural architectures of earth for gravity-driven water purification. As a result, the obtained biomimetic multilayer nanofibrous membranes exhibited three individual layers with designed functions; they were the inorganic nanofibrous layer to block the serious intrusion of oil to prevent the destructive fouling of the polymeric matrix; the submicron porous layer with designed honeycomb-like cavities to catch the smaller oil droplets and ensures a satisfactory water permeability; and the high porous fibrous substrate with larger pore size provided a template support and allows water to pass through quickly. Consequently, with the cooperation of these three functional layers, the resultant composite membrane possessed superior anti-oil-fouling property and robust oil-in-water emulsion separation performance with good separation efficiency and competitive permeation flux solely under the drive of gravity. The permeation flux of the membrane for the emulsion was up to 5163 L m -2 h -1 with a separation efficiency of 99.5%. We anticipate that our strategy could provide a facile route for developing a new generation of specific membranes for oily wastewater remediation.

Structural micro-porous carbon anode for rechargeable lithium-ion batteries

DOEpatents

Delnick, F.M.; Even, W.R. Jr.; Sylwester, A.P.; Wang, J.C.F.; Zifer, T.

1995-06-20

A secondary battery having a rechargeable lithium-containing anode, a cathode and a separator positioned between the cathode and anode with an organic electrolyte solution absorbed therein is provided. The anode comprises three-dimensional microporous carbon structures synthesized from polymeric high internal phase emulsions or materials derived from this emulsion source, i.e., granules, powders, etc. 6 figs.

Interfacial film stabilized W/O/W nano multiple emulsions loaded with green tea and lotus extracts: systematic characterization of physicochemical properties and shelf-storage stability

PubMed Central

2014-01-01

Background and aims Multiple emulsions have excellent encapsulating potential and this investigation has been aimed to encapsulate two different plant extracts as functional cosmetic agents in the W/O/W multiple emulsions and the resultant system’s long term stability has been determined in the presence of a thickener, hydroxypropyl methylcellulose (HPMC). Methods Multiple W/O/W emulsions have been generated using cetyl dimethicone copolyol as lipophilic emulsifier and a blend of polyoxyethylene (20) cetyl ether and cetomacrogol 1000® as hydrophilic emulsifiers. The generated multiple emulsions have been characterized with conductivity, pH, microscopic analysis, phase separation and rheology for a period of 30 days. Moreover, long term shelf-storage stability has been tested to understand the shelf-life by keeping the generated multiple emulsion formulations at 25 ± 10°C and at 40 ± 10% relative humidity for a period of 12 months. Results It has been observed that the hydrophilic emulsifiers and HPMC have considerably improved the stability of multiple emulsions for the followed period of 12 months at different storage conditions. These multiple emulsions have shown improved entrapment efficiencies concluded on the release rate of conductometric tracer entrapped in the inner aqueous phase of the multiple emulsions. Conclusion Multiple emulsions have been found to be stable for a longer period of time with promising characteristics. Hence, stable multiple emulsions loaded with green tea and lotus extracts could be explored for their cosmetic benefits. PMID:24885994

Vortex Advisory System Safety Analysis : Volume 1. Analytical Model

DOT National Transportation Integrated Search

1978-09-01

The Vortex Advisory System (VAS) is based on wind criterion--when the wind near the runway end is outside of the criterion, all interarrival Instrument Flight Rules (IFR) aircraft separations can be set at 3 nautical miles. Five years of wind data ha...

Vortex Advisory System : Volume 1. Effectiveness for Selected Airports.

DOT National Transportation Integrated Search

1980-05-01

The Vortex Advisory System (VAS) is based on wind criterion--when the wind near the runway end is outside of the criterion, all interarrival Instrument Flight Rules (IFR) aircraft separations can be set at 3 nautical miles. Five years of wind data ha...

Separations on water-ice. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dasgupta, P.K.

1998-07-01

This report focuses on processes to separate water frozen into ice. Research topics include the following: normal phase columnar chromatography; electrophoresis in a planar format; and zone melting type separations on a solid column of ice. Attempts were made to dope the emulsion with {beta}-cyclodextrin in order to separate commercially important chiral drugs such as Inderal.

Competitive displacement of sodium caseinate by low-molecular-weight emulsifiers and the effects on emulsion texture and rheology.

PubMed

Munk, M B; Larsen, F H; van den Berg, F W J; Knudsen, J C; Andersen, M L

2014-07-29

Low-molecular-weight (LMW) emulsifiers are used to promote controlled destabilization in many dairy-type emulsions in order to obtain stable foams in whippable products. The relation between fat globule aggregation induced by three LMW emulsifiers, lactic acid ester of monoglyceride (LACTEM), saturated monoglyceride (GMS), and unsaturated monoglyceride (GMU) and their effect on interfacial protein displacement was investigated. It was found that protein displacement by LMW emulsifiers was not necessary for fat globule aggregation in emulsions, and conversely fat globule aggregation was not necessarily accompanied by protein displacement. The three LMW emulsifiers had very different effects on emulsions. LACTEM induced shear instability of emulsions, which was accompanied by protein displacement. High stability was characteristic for emulsions with GMS where protein was displaced from the interface. Emulsions containing GMU were semisolid, but only low concentrations of protein were detected in the separated serum phase. The effects of LACTEM, GMS, and GMU may be explained by three different mechanisms involving formation of interfacial α-gel, pickering stabilization and increased exposure of bound casein to the water phase. The latter may facilitate partial coalescence. Stabilizing hydrocolloids did not have any effect on the LMW emulsifiers' ability to induce protein displacement.

Numerical simulation of incidence and sweep effects on delta wing vortex breakdown

NASA Technical Reports Server (NTRS)

Ekaterinaris, J. A.; Schiff, Lewis B.

1994-01-01

The structure of the vortical flowfield over delta wings at high angles of attack was investigated. Three-dimensional Navier-Stokes numerical simulations were carried out to predict the complex leeward-side flowfield characteristics, including leading-edge separation, secondary separation, and vortex breakdown. Flows over a 75- and a 63-deg sweep delta wing with sharp leading edges were investigated and compared with available experimental data. The effect of variation of circumferential grid resolution grid resolution in the vicinity of the wing leading edge on the accuracy of the solutions was addressed. Furthermore, the effect of turbulence modeling on the solutions was investigated. The effects of variation of angle of attack on the computed vortical flow structure for the 75-deg sweep delta wing were examined. At moderate angles of attack no vortex breakdown was observed. When a critical angle of attack was reached, bubble-type vortex breakdown was found. With further increase in angle of attack, a change from bubble-type breakdown to spiral-type vortex breakdown was predicted by the numerical solution. The effects of variation of sweep angle and freestream Mach number were addressed with the solutions on a 63-deg sweep delta wing.

Computational Study of the Effect of Slot Orientation on Synthetic Jet-Based Separation Control

DTIC Science & Technology

2012-01-01

Wind Turbine Blades,” Journal of Wind Energy, Vol. 13, Issue 2-3, 2009, pp. 221 – 237. [10] Crook, A. and Wood, N. J., “Measurements and...by these hairpin structures could be desirable for separation control. Roll-up of jets into vortex ring followed by tilting and stretching occurred...at an intermediate Reynolds number and velocity ratio. By increasing these two flow parameters, rapid penetration of the tilted vortex ring up to the

Bell’s measure and implementing quantum Fourier transform with orbital angular momentum of classical light

PubMed Central

Song, Xinbing; Sun, Yifan; Li, Pengyun; Qin, Hongwei; Zhang, Xiangdong

2015-01-01

We perform Bell’s measurement for the non-separable correlation between polarization and orbital angular momentum from the same classical vortex beam. The violation of Bell’s inequality for such a non-separable classical correlation has been demonstrated experimentally. Based on the classical vortex beam and non-quantum entanglement between the polarization and the orbital angular momentum, the Hadamard gates and conditional phase gates have been designed. Furthermore, a quantum Fourier transform has been implemented experimentally. PMID:26369424

Secondary Vortex Structures in Vortex Generator Induced Flow

NASA Astrophysics Data System (ADS)

Velte, Clara; Okulov, Valery; Hansen, Martin

2010-11-01

Passive rectangular vane actuators can induce a longitudinal vortex that redistributes the momentum in the boundary layer to control the flow. Recent experiments [1] as well as previous studies [2] have shown that a secondary vortex of opposite sign is generated along with the primary one, supposedly from local separation of the boundary layer due to the primary vortex. 2D flow visualizations of a vortex in the vicinity of a boundary support this hypothesis [3]. These secondary vortices are studied for various configurations -- single generator, counter- and co-rotating cascades. The objective is to study their removal through cancelation in cascades using Stereoscopic Particle Image Velocimetry and flow visualization.[4pt] [1] Velte, Hansen and Okulov, J. Fluid Mech. 619, 2009.[0pt] [2] Zhang, Int. J. Heat Fluid Flow 21 2000.[0pt] [3] Harris, Miller and Williamson, APS abstract 2009.

Current induced vortex wall dynamics in helical magnetic systems

NASA Astrophysics Data System (ADS)

Roostaei, Bahman

2015-03-01

Nontrivial topology of interfaces separating phases with opposite chirality in helical magnetic metals result in new effects as they interact with spin polarized current. These interfaces or vortex walls consist of a one dimensional array of vortex lines. We predict that adiabatic transfer of angular momentum between vortex array and spin polarized current will result in topological Hall effect in multi-domain samples. Also we predict that the motion of the vortex array will result in a new damping mechanism for magnetic moments based on Lenz's law. We study the dynamics of these walls interacting with electric current and use fundamental electromagnetic laws to quantify those predictions. On the other hand discrete nature of vortex walls affects their pinning and results in low depinning current density. We predict the value of this current using collective pinning theory.

Topological structures of vortex flow on a flying wing aircraft, controlled by a nanosecond pulse discharge plasma actuator

NASA Astrophysics Data System (ADS)

Du, Hai; Shi, Zhiwei; Cheng, Keming; Wei, Dechen; Li, Zheng; Zhou, Danjie; He, Haibo; Yao, Junkai; He, Chengjun

2016-06-01

Vortex control is a thriving research area, particularly in relation to flying wing or delta wing aircraft. This paper presents the topological structures of vortex flow on a flying wing aircraft controlled by a nanosecond plasma dielectric barrier discharge actuator. Experiments, including oil flow visualization and two-dimensional particle image velocimetry (PIV), were conducted in a wind tunnel with a Reynolds number of 0.5 × 106. Both oil and PIV results show that the vortex can be controlled. Oil topological structures on the aircraft surface coincide with spatial PIV flow structures. Both indicate vortex convergence and enhancement when the plasma discharge is switched on, leading to a reduced region of separated flow.

Flight-test experience of a helicopter encountering an airplane trailing vortex

NASA Technical Reports Server (NTRS)

Dunham, R. E., Jr.; Holbrook, G. T.; Campbell, R. L.; Van Gunst, R. W.; Mantay, W. R.

1976-01-01

This paper presents results of a flight-test experiment of a UH-1H helicopter encountering the vortex wake of a C-54 airplane. The helicopter was instrumented to record the pilot control inputs, determine the upset experience, and measure critical loads within the rotor system. During the flight-test program 132 penetrations of the vortex wake were made by the helicopter at separation distances from 3/8 to 6-1/2 nautical miles. Test results indicated that the helicopter upsets and the vortex induced blade loads experienced were minimal and well within safe limits. The upsets were very mild when compared to a typical response of a small airplane to the vortex wake of the C-54 airplane.

Vortex flow hysteresis

NASA Technical Reports Server (NTRS)

Cunningham, A. M., Jr.

1986-01-01

An experimental study was conducted to quantify the hysteresis associated with various vortex flow transition points and to determine the effect of planform geometry. The transition points observed consisted of the appearance (or disappearance) of trailing edge vortex burst and the transition to (or from) flat plate or totally separated flows. Flow visualization with smoke injected into the vortices was used to identify the transitions on a series of semi-span models tested in a low speed tunnel. The planforms tested included simple deltas (55 deg to 80 deg sweep), cranked wings with varying tip panel sweep and dihedral, and a straked wing. High speed movies at 1000 frames per second were made of the vortex flow visualization in order to better understand the dynamics of vortex flow, burst and transition.

An Aircraft Vortex Spacing System (AVOSS) for Dynamical Wake Vortex Spacing Criteria

NASA Technical Reports Server (NTRS)

Hinton, D. A.

1996-01-01

A concept is presented for the development and implementation of a prototype Aircraft Vortex Spacing System (AVOSS). The purpose of the AVOSS is to use current and short-term predictions of the atmospheric state in approach and departure corridors to provide, to ATC facilities, dynamical weather dependent separation criteria with adequate stability and lead time for use in establishing arrival scheduling. The AVOSS will accomplish this task through a combination of wake vortex transport and decay predictions, weather state knowledge, defined aircraft operational procedures and corridors, and wake vortex safety sensors. Work is currently underway to address the critical disciplines and knowledge needs so as to implement and demonstrate a prototype AVOSS in the 1999/2000 time frame.

Simple point vortex model for the relaxation of 2D superfluid turbulence in a Bose-Einstein condensate

NASA Astrophysics Data System (ADS)

Kim, Joon Hyun; Kwon, Woo Jin; Shin, Yong-Il

2016-05-01

In a recent experiment, it was found that the dissipative evolution of a corotating vortex pair in a trapped Bose-Einstein condensate is well described by a point vortex model with longitudinal friction on the vortex motion and the thermal friction coefficient was determined as a function of sample temperature. In this poster, we present a numerical study on the relaxation of 2D superfluid turbulence based on the dissipative point vortex model. We consider a homogeneous system in a cylindrical trap having randomly distributed vortices and implement the vortex-antivortex pair annihilation by removing a pair when its separation becomes smaller than a certain threshold value. We characterize the relaxation of the turbulent vortex states with the decay time required for the vortex number to be reduced to a quarter of initial number. We find the vortex decay time is inversely proportional to the thermal friction coefficient. In particular, we observe the decay times obtained from this work show good quantitative agreement with the experimental results in, indicating that in spite of its simplicity, the point vortex model reasonably captures the physics in the relaxation dynamics of the real system.

Wake Vortex Field Measurement Program at Memphis, Tennessee: Data Guide

NASA Technical Reports Server (NTRS)

Campbell, S. D.; Dasey, T. J.; Freehart, R. E.; Heinrichs, R. M.; Mathews, M. P.; Perras, G. H.; Rowe, G. S.

1997-01-01

Eliminating or reducing current restrictions in the air traffic control system due to wake vortex considerations would yield increased capacity, decreased delays, and cost savings. Current wake vortex separation standards are widely viewed as very conservative under most conditions. However, scientific uncertainty about wake vortex behavior under different atmospheric conditions remains a barrier to development of an adaptive vortex spacing system. The objective of the wake vortex field measurement efforts during December, 1994 and August, 1995 at Memphis, TN were to record wake vortex behavior for varying atmospheric conditions and types of aircraft. This effort is part of a larger effort by the NASA Langley Research Center to develop an Aircraft Vortex Spacing System (AVOSS) as an element of the Terminal Area Productivity (TAP) program. The TAP program is being performed in concert with the FAA Terminal Air Traffic Control Automation (TATCA) program and ATC Automation. Wake vortex behavior was observed using a mobile continuous-wave (CW) coherent laser Doppler radar (lidar) developed at Lincoln Laboratory. This lidar features a number of improvements over previous systems, including the first-ever demonstration of an automatic wake vortex detection and tracking algorithm.

Multiple emulsions as soft templates for the synthesis of multifunctional silicone porous particles.

PubMed

Vilanova, Neus; Kolen'ko, Yury V; Solans, Conxita; Rodríguez-Abreu, Carlos

2015-01-01

Multiple emulsion templating is a versatile strategy for the synthesis of porous particles. The present work addresses the synthesis of multifunctional poly(dimethylsiloxane) porous particles using multiple water-in-oil-in-water emulsions as soft templates with an oil phase constituted by a crosslinkable poly(dimethylsiloxane) (PDMS) oil. Herewith, the impact of the viscosity of PDMS oil (i.e., molecular weight) on the properties of both the emulsion templates and the resulting particles was evaluated. The viscosity of PDMS oil has a strong effect on the size and polydispersity of the emulsion templates as well as on the mechanical properties of the derived particles. The elastic modulus can be tuned by mixing PDMS oils of different viscosities to form bimodal crosslinked networks. Iron oxide nanoparticles can be readily incorporated into the emulsion templates to provide additional functionalities to the silicone particles, such as magnetic separation or magnetic hyperthermia. The synthesized composite magnetic particles were found to be useful as recoverable absorbent materials (e.g., for oil spills) by taking advantage of their high buoyancy and high hydrophobicity. Copyright © 2014 Elsevier Inc. All rights reserved.

Emulsions Stabilized by Chitosan-Modified Silica Nanoparticles: pH Control of Structure-Property Relations.

PubMed

Alison, Lauriane; Demirörs, Ahmet F; Tervoort, Elena; Teleki, Alexandra; Vermant, Jan; Studart, Andre R

2018-05-29

In food-grade emulsions, particles with an appropriate surface modification can be used to replace surfactants and potentially enhance the stability of emulsions. During the life cycle of products based on such emulsions, they can be exposed to a broad range of pH conditions and hence it is crucial to understand how pH changes affect stability of emulsions stabilized by particles. Here, we report on a comprehensive study of the stability, microstructure, and macroscopic behavior of pH-controlled oil-in-water emulsions containing silica nanoparticles modified with chitosan, a food-grade polycation. We found that the modified colloidal particles used as stabilizers behave differently depending on the pH, resulting in unique emulsion structures at multiple length scales. Our findings are rationalized in terms of the different emulsion stabilization mechanisms involved, which are determined by the pH-dependent charges and interactions between the colloidal building blocks of the system. At pH 4, the silica particles are partially hydrophobized through chitosan modification, favoring their adsorption at the oil-water interface and the formation of Pickering emulsions. At pH 5.5, the particles become attractive and the emulsion is stabilized by a network of agglomerated particles formed between the droplets. Finally, chitosan aggregates form at pH 9 and these act as the emulsion stabilizers under alkaline conditions. These insights have important implications for the processing and use of particle-stabilized emulsions. On one hand, changes in pH can lead to undesired macroscopic phase separation or coalescence of oil droplets. On the other hand, the pH effect on emulsion behavior can be harnessed in industrial processing, either to tune their flow response by altering the pH between processing stages or to produce pH-responsive emulsions that enhance the functionality of the emulsified end products.

In-flight flow visualization with pressure measurements at low speeds on the NASA F-18 high alpha research vehicle

NASA Technical Reports Server (NTRS)

Delfrate, John H.; Fisher, David F.; Zuniga, Fanny A.

1990-01-01

In-flight results from surface and off-surface flow visualizations and from extensive pressure distributions document the vortical flow on the leading edge extensions (LEX) and forebody of the NASA F-18 high alpha research vehicle for low speeds and angles of attack up to 50 degs. Surface flow visualization data, obtained using the emitted fluid technique, were used to define separation lines and laminar separation bubbles. Off-surface flow visualization data, obtained by smoke injection, were used to document both the path of the vortex cores and the location of vortex core breakdown. The location of vortex core breakdown correlated well with the loss of suction pressure on the LEX and with the flow visualization results from ground facilities. Surface flow separation lines on the LEX and forebody corresponded well with the end of pressure recovery under the vortical flows. Correlation of the pressures with wind tunnel results show fair to good correlation.

A Three-Dimensional Solution of Flows over Wings with Leading-Edge Vortex Separation. Part 1: Engineering Document

NASA Technical Reports Server (NTRS)

Brune, G. W.; Weber, J. A.; Johnson, F. T.; Lu, P.; Rubbert, P. E.

1975-01-01

A method of predicting forces, moments, and detailed surface pressures on thin, sharp-edged wings with leading-edge vortex separation in incompressible flow is presented. The method employs an inviscid flow model in which the wing and the rolled-up vortex sheets are represented by piecewise, continuous quadratic doublet sheet distributions. The Kutta condition is imposed on all wing edges. Computed results are compared with experimental data and with the predictions of the leading-edge suction analogy for a selected number of wing planforms over a wide range of angle of attack. These comparisons show the method to be very promising, capable of producing not only force predictions, but also accurate predictions of detailed surface pressure distributions, loads, and moments.

Formation of vortex wakes at flow separation from plate

NASA Astrophysics Data System (ADS)

Gorelov, D. N.; Govorova, A. I.

2017-05-01

The plane nonlinear initial boundary value problem about the separated flow past a plate set in motion at a constant velocity from the state of rest has been considered. Results of a numerical experiment which have allowed us to trace in detail the vortex-wake formation process behind a vertical plate are reported. It is shown that, after the beginning of the plate motion, several stable vortical structures, including a Karman street, form in succession behind the plate. It is found that, on the emergence of the Karman street, there occurs a sharp and substantial growth of vortex-wake intensity and hydrodynamic drag force with a pulsating time behavior. A conclusion about the origination, in this regime, of self-sustained oscillations of the liquid in the vicinity of the plate is drawn.

DEMONSTRATION BULLETIN: SFC OLEOFILTRATION SYSTEM - INPLANT SYSTEMS, INC.

EPA Science Inventory

SFC Oleofiltration System (SFC System) is a hydrocarbon recovery technology that utilizes an amine-coated ceramic granule to separate suspended and mechanically emulsified hydrocarbons from aqueous solutions. The granules reportedly also separate some chemical emulsions and red...

On the Lateral Static Stability of Low-Aspect-Ratio Rectangular Wings

NASA Astrophysics Data System (ADS)

Linehan, Thomas; Mohseni, Kamran

2017-11-01

Low-aspect-ratio rectangular wings experience a reduction in lateral static stability at angles of attack distinct from that of lift stall. Stereoscopic digital particle image velocimetry is used to elucidate the flow physics behind this trend. Rectangular wings of AR = 0.75, 1, 1.5, 3 were tested at side-slip angles β = -10° and 0° with angle of attack varied in the range α =10° -40° . In side-slip, the leading-edge separation region emerges on the leeward wing where leading-edge flow reattachment is highly intermittent due to vortex shedding. The tip vortex downwash of the AR < 1.5 wings is sufficient to restrict the shedding of leading-edge vorticity, enabling sustained lift from the leading-edge separation region to high angles of attack. The windward tip vortex grows in size with increasing angle of attack, occupying an increasingly larger percentage of the windward wing. At high angles of attack pre-lift stall, the windward tip vortex lifts off the wing, resulting in separated flow underneath it. The downwash of the AR = 3 wing is insufficient to reattach the leading-edge flow at high incidence. The flow stalls on the leeward wing with stalled flow expanding upstream toward the windward wing with increasing angle of attack.

Cell separations and the demixing of aqueous two phase polymer solutions in microgravity

NASA Technical Reports Server (NTRS)

Brooks, Donald E.; Bamberger, Stephan; Harris, J. M.; Van Alstine, James M.

1991-01-01

Partition in phase separated aqueous polymer solutions is a cell separation procedure thought to be adversely influenced by gravity. In preparation for performing cell partitioning experiments in space, and to provide general information concerning the demixing of immiscible liquids in low gravity, a series of phase separated aqueous polymer solutions have been flown on two shuttle flights. Fluorocarbon oil and water emulsions were also flown on the second flight. The aqueous polymer emulsions, which in one g demix largely by sedimentation and convection due to the density differences between the phases, demixed more slowly than on the ground and the final disposition of the phases was determined by the wetting of the container wall by the phases. The demixing behavior and kinetics were influenced by the phase volume ratio, physical properties of the systems and chamber wall interaction. The average domain size increased linearly with time as the systems demixed.

A multi-module microfluidic platform for continuous pre-concentration of water-soluble ions and separation of oil droplets from oil-in-water (O/W) emulsions using a DC-biased AC electrokinetic technique.

PubMed

Das, Dhiman; Phan, Dinh-Tuan; Zhao, Yugang; Kang, Yuejun; Chan, Vincent; Yang, Chun

2017-03-01

A novel continuous flow microfluidic platform specifically designed for environmental monitoring of O/W emulsions during an aftermath of oil spills is reported herein. Ionized polycyclic aromatic hydrocarbons which are toxic are readily released from crude oil to the surrounding water phase through the smaller oil droplets with enhanced surface area. Hence, a multi-module microfluidic device is fabricated to form ion enrichment zones in the water phase of O/W emulsions for the ease of detection and to separate micron-sized oil droplets from the O/W emulsions. Fluorescein ions in the water phase are used to simulate the presence of these toxic ions in the O/W emulsion. A DC-biased AC electric field is employed in both modules. In the first module, a nanoporous Nafion membrane is used for activating the concentration polarization effect on the fluorescein ions, resulting in the formation of stable ion enrichment zones in the water phase of the emulsion. A 35.6% amplification of the fluorescent signal is achieved in the ion enrichment zone; corresponding to 100% enrichment of the fluorescent dye concentration. In this module, the main inlet is split into two channels by using a Y-junction so that there are two outlets for the oil droplets. The second module located downstream of the first module consists of two oil droplet entrapment zones at two outlets. By switching on the appropriate electrodes, either one of the two oil droplet entrapment zones can be activated and the droplets can be blocked in the corresponding outlet. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Advanced analysis of polymer emulsions: Particle size and particle size distribution by field-flow fractionation and dynamic light scattering.

PubMed

Makan, Ashwell C; Spallek, Markus J; du Toit, Madeleine; Klein, Thorsten; Pasch, Harald

2016-04-15

Field flow fractionation (FFF) is an advanced fractionation technique for the analyses of very sensitive particles. In this study, different FFF techniques were used for the fractionation and analysis of polymer emulsions/latexes. As model systems, a pure acrylic emulsion and emulsions containing titanium dioxide were prepared and analyzed. An acrylic emulsion polymerization was conducted, continuously sampled from the reactor and subsequently analyzed to determine the particle size, radius of gyration in specific, of the latex particles throughout the polymerization reaction. Asymmetrical flow field-flow fractionation (AF4) and sedimentation field-flow fractionation (SdFFF), coupled to a multidetector system, multi-angle laser light scattering (MALLS), ultraviolet (UV) and refractive index (RI), respectively, were used to investigate the evolution of particle sizes and particle size distributions (PSDs) as the polymerization progressed. The obtained particle sizes were compared against batch-mode dynamic light scattering (DLS). Results indicated differences between AF4 and DLS results due to DLS taking hydration layers into account, whereas both AF4 and SdFFF were coupled to MALLS detection, hence not taking the hydration layer into account for size determination. SdFFF has additional separation capabilities with a much higher resolution compared to AF4. The calculated radii values were 5 nm larger for SdFFF measurements for each analyzed sample against the corresponding AF4 values. Additionally a low particle size shoulder was observed for SdFFF indicating bimodality in the reactor very early during the polymerization reaction. Furthermore, different emulsions were mixed with inorganic species used as additives in cosmetics and coatings such as TiO2. These complex mixtures of species were analyzed to investigate the retention and particle interaction behavior under different AF4 experimental conditions, such as the mobile phase. The AF4 system was coupled online to inductively coupled plasma mass spectrometry (ICP-MS) for elemental speciation and identification of the inorganic additive. SdFFF had a larger separation power to distinguish different particle size populations whereas AF4 had the capability of separating the organic particles and inorganic TiO2 particles, with high resolution. Copyright © 2016 Elsevier B.V. All rights reserved.

[Study on separation of essential oil of Caryophylli flos from oil-in-water emulsion by microfiltration].

PubMed

Han, Zhifeng; Shen, Jie; Guo, Liwei; Fan, Wenlin

2011-01-01

To separate essential oil of Caryophyllix flos from oil-in-water emulsion, and to enrich the essential oil by microfiltration (MF). Using membrane flux and removal rate of COD as the indicatrixes, the membrane material as well as the operating conditions containing pressure, surface speed, temperature were optimized. The results showed that QWLM membrane of hydrophilic is the proper membrane, and the best operating conditions was at 0.06 MPa, 60 degrees C, and 150 r min(-1) stir speed. It can be concluded that MF is a reasonable way to enrich essential oil of C. flox.

Morphological study of polymethyl methacrylate microcapsules filled with self-healing agents

NASA Astrophysics Data System (ADS)

Ahangaran, Fatemeh; Hayaty, Mehran; Navarchian, Amir H.

2017-03-01

Polymethyl methacrylate (PMMA) microcapsules filled with epoxy prepolymer, 3-aminomethyl-3,5,5-trimethylcyclohexylamine, and pentaerythritol tetrakis (3-mercaptopropionate) as healing agents have been prepared separately through internal phase separation method for self-healing purposes. PMMA with two different molecular weights (M bar1 = 36,000 g/mol and M bar2 = 550,000 g/mol) were used with two types of different emulsifiers (ionic and polymeric) to prepare microcapsules. The morphology of healing agent microcapsules was investigated using field emission scanning electron microscopy (FESEM). It was found that PMMA microcapsules separately filled with epoxy and amine had core-shell morphologies with smooth surfaces. The mercaptan/PMMA particles exhibited core-shell and acorn-shape morphologies. The surface morphology of mercaptan microcapsules changed from holed to plain in different emulsion systems. The spreading coefficient (S) of phases in the prepared emulsion systems were calculated from interfacial tension (σ) and contact angle (θ) measurements. The theoretical equilibrium morphology of PMMA microcapsules was predicted according to spreading coefficient values of phases in emulsion systems. It was also found that the surface morphology of PMMA microcapsules depended strongly on the nature of the core, molecular weight of PMMA, type and concentration of emulsifier.

Aeroelastic loads prediction for an arrow wing. Task 1: Evaluation of R. P. White's method

NASA Technical Reports Server (NTRS)

Borland, C. J.; Manro, M. E.

1983-01-01

The separated flow method is evaluated. This method was developed for moderately swept wings with multiple, constant strength vortex systems. The flow on the highly swept wing used in this evaluation is characterized by a single vortex system of continuously varying strength.

Discrimination of orbital angular momentum modes of the terahertz vortex beam using a diffractive mode transformer.

PubMed

Liu, Changming; Wei, Xuli; Niu, Liting; Wang, Kejia; Yang, Zhengang; Liu, Jinsong

2016-06-13

We present an efficient method to discriminate orbital angular momentum (OAM) of the terahertz (THz) vortex beam using a diffractive mode transformer. The mode transformer performs a log-polar coordinate transformation of the input THz vortex beam, which consists of two 3D-printed diffractive elements. A following lens separates each transformed OAM mode to a different lateral position in its focal plane. This method enables a simultaneous measurement over multiple OAM modes of the THz vortex beam. We experimentally demonstrate the measurement of seven individual OAM modes and two multiplexed OAM modes, which is in good agreement with simulations.

Vortex methods for separated flows

NASA Technical Reports Server (NTRS)

Spalart, Philippe R.

1988-01-01

The numerical solution of the Euler or Navier-Stokes equations by Lagrangian vortex methods is discussed. The mathematical background is presented and includes the relationship with traditional point-vortex studies, convergence to smooth solutions of the Euler equations, and the essential differences between two and three-dimensional cases. The difficulties in extending the method to viscous or compressible flows are explained. Two-dimensional flows around bluff bodies are emphasized. Robustness of the method and the assessment of accuracy, vortex-core profiles, time-marching schemes, numerical dissipation, and efficient programming are treated. Operation counts for unbounded and periodic flows are given, and two algorithms designed to speed up the calculations are described.

Oil-in-oil emulsions stabilised solely by solid particles.

PubMed

Binks, Bernard P; Tyowua, Andrew T

2016-01-21

A brief review of the stabilisation of emulsions of two immiscible oils is given. We then describe the use of fumed silica particles coated with either hydrocarbon or fluorocarbon groups in acting as sole stabilisers of emulsions of various vegetable oils with linear silicone oils (PDMS) of different viscosity. Transitional phase inversion of emulsions, containing equal volumes of the two oils, from silicone-in-vegetable (S/V) to vegetable-in-silicone (V/S) occurs upon increasing the hydrophobicity of the particles. Close to inversion, emulsions are stable to coalescence and gravity-induced separation for at least one year. Increasing the viscosity of the silicone oil enables stable S/V emulsions to be prepared even with relatively hydrophilic particles. Predictions of emulsion type from calculated contact angles of a silica particle at the oil-oil interface are in agreement with experiment provided a small polar contribution to the surface energy of the oils is included. We also show that stable multiple emulsions of V/S/V can be prepared in a two-step procedure using two particle types of different hydrophobicity. At fixed particle concentration, catastrophic phase inversion of emulsions from V/S to S/V can be effected by increasing the volume fraction of vegetable oil. Finally, in the case of sunflower oil + 20 cS PDMS, the study is extended to particles other than silica which differ in chemical type, particle size and particle shape. Consistent with the above findings, we find that only sufficiently hydrophobic particles (clay, zinc oxide, silicone, calcium carbonate) can act as efficient V/S emulsion stabilisers.

A Method for Computing the Core Flow in Three-Dimensional Leading-Edge Vortices. Ph.D. Thesis - North Carolina State Univ.

NASA Technical Reports Server (NTRS)

Luckring, J. M.

1985-01-01

A theory is presented for calculating the flow in the core of a separation-induced leading-edge vortex. The method is based on matching inner and outer representations of the vortex. The inner model of the vortex is based on the quasicylindrical Navier-Stokes equations; the flow is assumed to be steady, axially symmetric, and incompressible and in addition, gradients in the radial direction are assumed to be much larger then gradients in the axial direction. The outer model is based on the three-dimensional free-vortex-sheet theory, a higher-order panel method which solves the Prandtl-Glauert equation including nonlinear boundary conditions pertinent to the concentrated vorticity representation of the leading edge vortex. The resultant flow is evaluated a posteriori for evidence of incipient vortex breakdown and the critical helix angle concept, in conjunction with an adverse longitudinal pressure gradient, is found to correlate well with the occurrence of vortex breakdown at the trailing edge of delta, arrow, and diamond wings.

Logic operations based on magnetic-vortex-state networks.

PubMed

Jung, Hyunsung; Choi, Youn-Seok; Lee, Ki-Suk; Han, Dong-Soo; Yu, Young-Sang; Im, Mi-Young; Fischer, Peter; Kim, Sang-Koog

2012-05-22

Logic operations based on coupled magnetic vortices were experimentally demonstrated. We utilized a simple chain structure consisting of three physically separated but dipolar-coupled vortex-state Permalloy disks as well as two electrodes for application of the logical inputs. We directly monitored the vortex gyrations in the middle disk, as the logical output, by time-resolved full-field soft X-ray microscopy measurements. By manipulating the relative polarization configurations of both end disks, two different logic operations are programmable: the XOR operation for the parallel polarization and the OR operation for the antiparallel polarization. This work paves the way for new-type programmable logic gates based on the coupled vortex-gyration dynamics achievable in vortex-state networks. The advantages are as follows: a low-power input signal by means of resonant vortex excitation, low-energy dissipation during signal transportation by selection of low-damping materials, and a simple patterned-array structure.

Fast nanoscale addressability of nitrogen-vacancy spins via coupling to a dynamic ferromagnetic vortex

PubMed Central

Wolf, M. S.; Badea, R.; Berezovsky, J.

2016-01-01

The core of a ferromagnetic vortex domain creates a strong, localized magnetic field, which can be manipulated on nanosecond timescales, providing a platform for addressing and controlling individual nitrogen-vacancy centre spins in diamond at room temperature, with nanometre-scale resolution. Here, we show that the ferromagnetic vortex can be driven into proximity with a nitrogen-vacancy defect using small applied magnetic fields, inducing significant nitrogen-vacancy spin splitting. We also find that the magnetic field gradient produced by the vortex is sufficient to address spins separated by nanometre-length scales. By applying a microwave-frequency magnetic field, we drive both the vortex and the nitrogen-vacancy spins, resulting in enhanced coherent rotation of the spin state. Finally, we demonstrate that by driving the vortex on fast timescales, sequential addressing and coherent manipulation of spins is possible on ∼100 ns timescales. PMID:27296550

Optical superimposed vortex beams generated by integrated holographic plates with blazed grating

NASA Astrophysics Data System (ADS)

Zhang, Xue-Dong; Su, Ya-Hui; Ni, Jin-Cheng; Wang, Zhong-Yu; Wang, Yu-Long; Wang, Chao-Wei; Ren, Fei-Fei; Zhang, Zhen; Fan, Hua; Zhang, Wei-Jie; Li, Guo-Qiang; Hu, Yan-Lei; Li, Jia-Wen; Wu, Dong; Chu, Jia-Ru

2017-08-01

In this paper, we demonstrate that the superposition of two vortex beams with controlled topological charges can be realized by integrating two holographic plates with blazed grating. First, the holographic plate with blazed grating was designed and fabricated by laser direct writing for generating well-separated vortex beam. Then, the relationship between the periods of blazed grating and the discrete angles of vortex beams was systemically investigated. Finally, through setting the discrete angle and different revolving direction of the holographic plates, the composite fork-shaped field was realized by the superposition of two vortex beams in a particular position. The topological charges of composite fork-shaped field (l = 1, 0, 3, and 4) depend on the topological charges of compositional vortex beams, which are well agreed with the theoretical simulation. The method opens up a wide range of opportunities and possibilities for applying in optical communication, optical manipulations, and photonic integrated circuits.

Fast nanoscale addressability of nitrogen-vacancy spins via coupling to a dynamic ferromagnetic vortex

DOE PAGES

Wolf, M. S.; Badea, R.; Berezovsky, J.

2016-06-14

The core of a ferromagnetic vortex domain creates a strong, localized magnetic field, which can be manipulated on nanosecond timescales, providing a platform for addressing and controlling individual nitrogen-vacancy centre spins in diamond at room temperature, with nanometre-scale resolution. Here, we show that the ferromagnetic vortex can be driven into proximity with a nitrogen-vacancy defect using small applied magnetic fields, inducing significant nitrogen-vacancy spin splitting. We also find that the magnetic field gradient produced by the vortex is sufficient to address spins separated by nanometre-length scales. By applying a microwave-frequency magnetic field, we drive both the vortex and the nitrogen-vacancymore » spins, resulting in enhanced coherent rotation of the spin state. Lastly, we demonstrate that by driving the vortex on fast timescales, sequential addressing and coherent manipulation of spins is possible on ~ 100 ns timescales.« less

Quasi-Porous Plug With Vortex Chamber

NASA Technical Reports Server (NTRS)

Walsh, J. V.

1985-01-01

Pressure-letdown valve combines quasi-porous-plug and vortex-chamber in one controllable unit. Valve useful in fossil-energy plants for reducing pressures in such erosive two-phase process streams as steam/water, coal slurries, or combustion gases with entrained particles. Quasi-Porous Plug consists of plenums separated by perforated plates. Number or size of perforations increases with each succeeding stage to compensate for expansion. In Vortex Chamber, control flow varies to control swirl and therefore difference between inlet and outlet pressures.

A theoretical investigation of the aerodynamics of low-aspect-ratio wings with partial leading-edge separation

NASA Technical Reports Server (NTRS)

Mehrotra, S. C.; Lan, C. E.

1978-01-01

A numerical method is developed to predict distributed and total aerodynamic characteristics for low aspect-ratio wings with partial leading-edge separation. The flow is assumed to be steady and inviscid. The wing boundary condition is formulated by the quasi-vortex-lattice method. The leading-edge separated vortices are represented by discrete free vortex elements which are aligned with the local velocity vector at mid-points to satisfy the force free condition. The wake behind the trailing-edge is also force free. The flow tangency boundary condition is satisfied on the wing, including the leading- and trailing-edges. Comparison of the predicted results with complete leading-edge separation has shown reasonably good agreement. For cases with partial leading-edge separation, the lift is found to be highly nonlinear with angle of attack.

Container effects on the physicochemical properties of parenteral lipid emulsions.

PubMed

Gonyon, Thomas; Carter, Phillip W; Dahlem, Olivier; Denet, Anne-Rose; Owen, Heather; Trouilly, Jean-Luc

2008-01-01

We evaluated the effects of glass and plastic containers on the physicochemical properties of parenteral nutrition lipid emulsions and total nutrient admixtures with an emphasis on globule size distribution and colloidal stability. A commercial lipid emulsion, 20% ClinOleic, was separated into glass (type II soda-lime-silica) and plastic (polypropylene multilayer) containers, sterilized, and then stored for 16 wk at 40 degrees C. Globule size distribution, pH, and zeta potential measurements were made every 4 wk. Admixtures derived from parent lipid emulsions were tested after admixing (t = 0), storage for 7 d at 5 degrees C plus 24 h at 25 degrees C (t = 7 + 1), and then after an additional 3 d at 25 degrees C (t = 7 + 4). The parent lipid emulsions in glass and plastic containers exhibited identical time-dependent behavior with respect to mean globule size, percentage of oil droplets >or=5 mum, pH, and zeta potential measurements. The percentages of oil droplets >or=5 mum of all test conditions remained well below the United States Pharmacopeia <729> limits of 0.05%. The total nutrient admixture time-dependent physicochemical characteristics were also found to be independent of the parent lipid emulsion container type. Plastic and glass containers were found to be suitable, safe, and indistinguishable with respect to physicochemical stability of a representative parenteral nutrition lipid emulsion and total nutrient admixtures derived from the parent lipid emulsion.

Cross-linking proteins by laccase: Effects on the droplet size and rheology of emulsions stabilized by sodium caseinate.

PubMed

Sato, A C K; Perrechil, F A; Costa, A A S; Santana, R C; Cunha, R L

2015-09-01

The aim of this work was to evaluate the influence of laccase and ferulic acid on the characteristics of oil-in-water emulsions stabilized by sodium caseinate at different pH (3, 5 and 7). Emulsions were prepared by high pressure homogenization of soybean oil with sodium caseinate solution containing varied concentrations of laccase (0, 1 and 5mg/mL) and ferulic acid (5 and 10mM). Laccase treatment and pH exerted a strong influence on the properties with a consequent effect on stability, structure and rheology of emulsions stabilized by Na-caseinate. At pH7, O/W emulsions were kinetically stable due to the negative protein charge which enabled electrostatic repulsion between oil droplets resulting in an emulsion with small droplet size, low viscosity, pseudoplasticity and viscoelastic properties. The laccase treatment led to emulsions showing shear-thinning behavior as a result of a more structured system. O/W emulsions at pH5 and 3 showed phase separation due to the proximity to protein pI, but the laccase treatment improved their stability of emulsions especially at pH3. At pH3, the addition of ferulic acid and laccase produced emulsions with larger droplet size but with narrower droplet size distribution, increased viscosity, pseudoplasticity and viscoelastic properties (gel-like behavior). Comparing laccase treatments, the combined addition of laccase and ferulic acid generally produced emulsions with lower stability (pH5), larger droplet size (pH3, 5 and 7) and higher pseudoplasticity (pH5 and 7) than emulsion with only ferulic acid. The results suggested that the cross-linking of proteins by laccase and ferulic acid improved protein emulsifying properties by changing functional mechanisms of the protein on emulsion structure and rheology, showing that sodium caseinate can be successfully used in acid products when treated with laccase. Copyright © 2015 Elsevier Ltd. All rights reserved.

Electrostatic coalescence system with independent AC and DC hydrophilic electrodes

DOEpatents

Hovarongkura, A. David; Henry, Jr., Joseph D.

1981-01-01

An improved electrostatic coalescence system is provided in which independent AC and DC hydrophilic electrodes are employed to provide more complete dehydration of an oil emulsion. The AC field is produced between an AC electrode array and the water-oil interface wherein the AC electrode array is positioned parallel to the interface which acts as a grounded electrode. The emulsion is introduced into the AC field in an evenly distributed manner at the interface. The AC field promotes drop-drop and drop-interface coalescence of the water phase in the entering emulsion. The continuous oil phase passes upward through the perforated AC electrode array and enters a strong DC field produced between closely spaced DC electrodes in which small dispersed droplets of water entrained in the continuous phase are removed primarily by collection at hydrophilic DC electrodes. Large droplets of water collected by the electrodes migrate downward through the AC electrode array to the interface. All phase separation mechanisms are utilized to accomplish more complete phase separation.

Development and validation of a simple high-performance liquid chromatography analytical method for simultaneous determination of phytosterols, cholesterol and squalene in parenteral lipid emulsions.

PubMed

Novak, Ana; Gutiérrez-Zamora, Mercè; Domenech, Lluís; Suñé-Negre, Josep M; Miñarro, Montserrat; García-Montoya, Encarna; Llop, Josep M; Ticó, Josep R; Pérez-Lozano, Pilar

2018-02-01

A simple analytical method for simultaneous determination of phytosterols, cholesterol and squalene in lipid emulsions was developed owing to increased interest in their clinical effects. Method development was based on commonly used stationary (C 18 , C 8 and phenyl) and mobile phases (mixtures of acetonitrile, methanol and water) under isocratic conditions. Differences in stationary phases resulted in peak overlapping or coelution of different peaks. The best separation of all analyzed compounds was achieved on Zorbax Eclipse XDB C 8 (150 × 4.6 mm, 5 μm; Agilent) and ACN-H 2 O-MeOH, 80:19.5:0.5 (v/v/v). In order to achieve a shorter time of analysis, the method was further optimized and gradient separation was established. The optimized analytical method was validated and tested for routine use in lipid emulsion analyses. Copyright © 2017 John Wiley & Sons, Ltd.

A comparative study of Full Navier-Stokes and Reduced Navier-Stokes analyses for separating flows within a diffusing inlet S-duct

NASA Technical Reports Server (NTRS)

Anderson, B. H.; Reddy, D. R.; Kapoor, K.

1993-01-01

A three-dimensional implicit Full Navier-Stokes (FNS) analysis and a 3D Reduced Navier Stokes (RNS) initial value space marching solution technique has been applied to a class of separated flow problems within a diffusing S-duct configuration characterized by vortex-liftoff. Both the FNS and the RNS solution technique were able to capture the overall flow physics of vortex lift-off, and gave remarkably similar results which agreed reasonably well with the experimental measured averaged performance parameters of engine face total pressure recovery and distortion. However, the Full Navier-Stokes and Reduced Navier-Stokes also consistently predicted separation further downstream in the M2129 inlet S-duct than was indicated by experimental data, thus compensating errors were present in the two Navier-Stokes analyses. The difficulties encountered in the Navier-Stokes separations analyses of the M2129 inlet S-duct center primarily on turbulence model issues, and these focused on two distinct but different phenomena, namely, (1) characterization of low skin friction adverse pressure gradient flows, and (2) description of the near wall behavior of flows characterized by vortex lift-off.

Compact CFB: The next generation CFB boiler

DOE Office of Scientific and Technical Information (OSTI.GOV)

Utt, J.

1996-12-31

The next generation of compact circulating fluidized bed (CFB) boilers is described in outline form. The following topics are discussed: compact CFB = pyroflow + compact separator; compact CFB; compact separator is a breakthrough design; advantages of CFB; new design with substantial development history; KUHMO: successful demo unit; KUHMO: good performance over load range with low emissions; KOKKOLA: first commercial unit and emissions; KOKKOLA: first commercial unit and emissions; compact CFB installations; next generation CFB boiler; grid nozzle upgrades; cast segmented vortex finders; vortex finder installation; ceramic anchors; pre-cast vertical bullnose; refractory upgrades; and wet gunning.

Analysis of Multiallelic CNVs by Emulsion Haplotype Fusion PCR.

PubMed

Tyson, Jess; Armour, John A L

2017-01-01

Emulsion-fusion PCR recovers long-range sequence information by combining products in cis from individual genomic DNA molecules. Emulsion droplets act as very numerous small reaction chambers in which different PCR products from a single genomic DNA molecule are condensed into short joint products, to unite sequences in cis from widely separated genomic sites. These products can therefore provide information about the arrangement of sequences and variants at a larger scale than established long-read sequencing methods. The method has been useful in defining the phase of variants in haplotypes, the typing of inversions, and determining the configuration of sequence variants in multiallelic CNVs. In this description we outline the rationale for the application of emulsion-fusion PCR methods to the analysis of multiallelic CNVs, and give practical details for our own implementation of the method in that context.

Hierarchically porous materials from layer-by-layer photopolymerization of high internal phase emulsions.

PubMed

Sušec, Maja; Ligon, Samuel Clark; Stampfl, Jürgen; Liska, Robert; Krajnc, Peter

2013-06-13

A combination of high internal phase emulsion (HIPE) templating and additive manufacturing technology (AMT) is applied for creating hierarchical porosity within an acrylate and acrylate/thiol-based polymer network. The photopolymerizable formulation is optimized to produce emulsions with a volume fraction of droplet phase greater than 80 vol%. Kinetic stability of the emulsions is sufficient enough to withstand in-mold curing or computer-controlled layer-by-layer stereolithography without phase separation. By including macroscale cellular cavities within the build file, a level of controlled porosity is created simultaneous to the formation of the porous microstructure of the polyHIPE. The hybrid HIPE-AMT technique thus provides hierarchically porous materials with mechanical properties tailored by the addition of thiol chain transfer agent. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Separation of oil-water-sludge emulsions coming from palm oil mill process through microwave techniques.

PubMed

Pérez-Páez, Rocío; Catalá-Civera, José Manuel; García-Baños, Beatriz; Castillo, Edgar F; Bastos, Johanna M; Zambrano, Luz S

2008-01-01

The palm oil mills extraction process requires the separation of oil-water-sludge emulsions. For this purpose, the use of sedimentation and/or centrifugation techniques have been required until now. However, significant losses persist in different process flows and new methods are needed to further decrease them, such as methods based on electromagnetic waves application. In the study, emulsions obtained from two flow processes, namely press liquor stream (PL) and recovered stream of the centrifugal step (RC), were exposed to microwave radiation with different exposure times. In the case of the press liquor stream, different oil/water dilution ratios were also studied. The sedimentation speed and efficiency were studied for the irradiated samples and compared to those obtained for the same fluids with no radiation. Also, chromatographic tests were performed on the recovered oil to determine the effect on the oil quality after microwave radiation. The obtained results allow us to conclude that microwave exposure during periods below 1 minute lead to better sedimentation speed and efficiency. It was observed that microwaves facilitate the break of the charges and polarities balances in the emulsions at considerably lower temperatures than the corresponding in the conventional process, without affecting the recovered oil quality.

Effect of Eccentricity in Compound Droplets Subject to a Simple Shear Flow

NASA Astrophysics Data System (ADS)

Kim, Sangkyu; Dabiri, Sadegh

2016-11-01

A double emulsion, or a compound droplet, is a system where two liquids are separated by an immiscible third liquid, thereby forming an emulsion inside an emulsion. Compound drops benefit from this separation in applications such food sciences, microfluidics, pharmaceutical engineering, and polymer sciences. While the subjects of double emulsion preparations, deformations, and breakup mechanisms are well-explored, the time-evolution of non-concentric compound drops has received far less analytical or computational scrutiny. In this work, we present computational results using finite volume method with front-tracking approach for initially spherical and non-concentric compound drops in a shear flow. Our findings for low Reynolds number flows show that: 1. The surrounding shear flow to the outer drop induces a rotational velocity field inside it, causing the inner drop to tumble with the flow, 2. the tumbling motion persists in time, and acts to increase the eccentricity of the compound drop, and 3. the hemisection-plane to the outer drop that is aligned with the plane of the simple shear defines an unstable equilibrium for inner drop's center, and the inner drop continuously drifts away from that plane. This work suggests a means of favorably configuring compound drops suitable for breakups, and helps to understand their migration in channel flows.

VERIFICATION OF HIGH-RATE SEPARATION DEVICES UNDER THE WET-WEATHER FLOW TECHNOLOGIES PILOT - ETV PROGRAM

EPA Science Inventory

This paper presents performance verification data on two types of high-rate separation devices utilized for solids removal: Vortex separation devices (a class of physical treatment technologies that use cylindrical chambers to create centrifugal forces that separate settleable so...

Separation of cucurbitane triterpenoids from bitter melon drinks and determination of partition coefficients using vortex-assisted dispersive liquid-phase microextraction followed by UHPLC analysis

USDA-ARS?s Scientific Manuscript database

A rapid, effective technique applying vortex-assisted liquid–liquid microextraction (VALLME) prior to ultra high performance liquid chromatography-evaporating light scattering detectection/ mass spectroscopy (UHPLC-ELSD/MS) determination was developed for the analysis of four cucurbitane triterpenoi...

Numerical simulation of the tip vortex off a low-aspect-ratio wing at transonic speed

NASA Technical Reports Server (NTRS)

Mansour, N. N.

1984-01-01

The viscous transonic flow around a low aspect ratio wing was computed by an implicit, three dimensional, thin-layer Navier-Stokes solver. The grid around the geometry of interest is obtained numerically as a solution to a Dirichlet problem for the cube. A low aspect ratio wing with large sweep, twist, taper, and camber is the chosen geometry. The topology chosen to wrap the mesh around the wing with good tip resolution is a C-O type mesh. The flow around the wing was computed for a free stream Mach number of 0.82 at an angle of attack of 5 deg. At this Mach number, an oblique shock forms on the upper surface of the wing, and a tip vortex and three dimensional flow separation off the wind surface are observed. Particle path lines indicate that the three dimensional flow separation on the wing surface is part of the roots of the tip vortex formation. The lifting of the tip vortex before the wing trailing edge is observed by following the trajectory of particles release around the wing tip.

Nonlinear effects in the bounded dust-vortex flow in plasma

NASA Astrophysics Data System (ADS)

Laishram, Modhuchandra; Sharma, Devendra; Chattopdhyay, Prabal K.; Kaw, Predhiman K.

2017-03-01

The vortex structures in a cloud of electrically suspended dust in a streaming plasma constitutes a driven system with a rich nonlinear flow regime. Experimentally recovered toroidal formations of this system have motivated study of its volumetrically driven-dissipative vortex flow dynamics using two-dimensional hydrodynamics in the incompressible Navier-Stokes regime. Nonlinear equilibrium solutions are obtained for this system where a nonuniformly driven two-dimensional dust flow exhibits distinct regions of localized accelerations and strong friction caused by stationary fluids at the confining boundaries resisting the dust flow. In agreement with observations in experiments, it is demonstrated that the nonlinear effects appear in the limit of small viscosity, where the primary vortices form scaling with the most dominant spatial scales of the domain topology and develop separated virtual boundaries along their periphery. This separation is triggered beyond a critical dust viscosity that signifies a structural bifurcation. Emergence of uniform vorticity core and secondary vortices with a newer level of identical dynamics highlights the applicability of the studied dynamics to gigantic vortex flows, such as the Jovian great red spot, to microscopic biophysical intracellular activity.

Microparticle Separation by Cyclonic Separation

NASA Astrophysics Data System (ADS)

Karback, Keegan; Leith, Alexander

2017-11-01

The ability to separate particles based on their size has wide ranging applications from the industrial to the medical. Currently, cyclonic separators are primarily used in agriculture and manufacturing to syphon out contaminates or products from an air supply. This has led us to believe that cyclonic separation has more applications than the agricultural and industrial. Using the OpenFoam computational package, we were able to determine the flow parameters of a vortex in a cyclonic separator in order to segregate dust particles to a cutoff size of tens of nanometers. To test the model, we constructed an experiment to separate a test dust of various sized particles. We filled a chamber with Arizona test dust and utilized an acoustic suspension technique to segregate particles finer than a coarse cutoff size and introduce them into the cyclonic separation apparatus where they were further separated via a vortex following our computational model. The size of the particles separated from this experiment will be used to further refine our model. Metropolitan State University of Denver, Colorado University of Denver, Dr. Randall Tagg, Dr. Richard Krantz.

Advection within side-by-side liquid micro-cylinders in a cross-flow

NASA Astrophysics Data System (ADS)

Dong, Qingming; Sau, Amalendu

2017-11-01

The gaseous SO2 entrainment from outer air stream and dispersion in binary and ternary liquid micro-cylinders appearing side-by-side are examined hereby. The separation/attachment regulated non-uniform interfacial momentum exchange creates main stream driven "primary" and shear reversed "secondary" vortices in the liquid cylinders. At separation points, the sense of rotation of the generated "primary-secondary" vortex pair remains inward directed. We define such a vortex pair as the "inflow" type. However, at stagnation or attachment points, the sense of rotation of a "primary-primary" or "secondary-secondary" vortex pair remains outward directed, and such a vortex pair is defined as the "outflow" type. For the coupled water cylinders facing an oncoming stream contaminated by gaseous SO2, its absorption and internal transport are effectively controlled by dominant "inflow" and "outflow" natured dynamics of the said vortex pairs, besides by diffusion. The evolving "inflow" natured "primary-secondary" vortex pairs at separation points actively entrain the outer SO2, whereas the "outflow" natured vortex-pairs oppose SO2 entry through the stagnation regions. Moreover, the blockage induced steady-symmetric, steady-deflected, and flip-flopping air-jets through gaps, for varied gap-ratio (1 ≤ G/R ≤ 4) and Reynolds number (30 ≤ Re ≤ 160), create distinctive impact both on quantitative SO2 absorption (mso2 ') and convective nature of the SO2 transport in upper, lower, and middle cylinders, by virtue of modified strength and size of the inflow and outflow paired vortices. The present study shows that the tiny "secondary vortices" play important roles in SO2 entrainment and in effectively controlling the local absorption rate Rs o2. The sudden acceleration and upward/downward deflection of gap-flows enhanced near-neck advective SO2 entrainment by suitably strengthening the "inflow" natured local vortex dynamics. Conversely, for the reduced size of secondary vortices, the saturation becomes delayed. In addition, for decreased vertical spacing of micro-cylinders (R = 40 μm) falling below the diameter-length "2R," the SO2 absorption (mso2 ') only gets slower. We provide extensive analysis of two-phase transport phenomena in terms of interactive shear-stress, pressure, and characteristic time-ratio "Tr" of advection-diffusion processes, for varied G/R, Re, and liquid phase Peclet number "Pel" (96 ≤ Pel ≤ 1333), to present a better insight into the governing physics.

Double emulsion formation through hierarchical flow-focusing microchannel

NASA Astrophysics Data System (ADS)

Azarmanesh, Milad; Farhadi, Mousa; Azizian, Pooya

2016-03-01

A microfluidic device is presented for creating double emulsions, controlling their sizes and also manipulating encapsulation processes. As a result of three immiscible liquids' interaction using dripping instability, double emulsions can be produced elegantly. Effects of dimensionless numbers are investigated which are Weber number of the inner phase (Wein), Capillary number of the inner droplet (Cain), and Capillary number of the outer droplet (Caout). They affect the formation process, inner and outer droplet size, and separation frequency. Direct numerical simulation of governing equations was done using volume of fluid method and adaptive mesh refinement technique. Two kinds of double emulsion formation, the two-step and the one-step, were simulated in which the thickness of the sheath of double emulsions can be adjusted. Altering each dimensionless number will change detachment location, outer droplet size and droplet formation period. Moreover, the decussate regime of the double-emulsion/empty-droplet is observed in low Wein. This phenomenon can be obtained by adjusting the Wein in which the maximum size of the sheath is discovered. Also, the results show that Cain has significant influence on the outer droplet size in the two-step process, while Caout affects the sheath in the one-step formation considerably.

Temperature-Induced Protein Release from Water-in-Oil-in-Water Double Emulsions

PubMed Central

Rojas, Edith C.; Staton, Jennifer A.; John, Vijay T.; Papadopoulos, Kyriakos D.

2009-01-01

A model water-in-oil-in-water (W1/O/W2) double emulsion was prepared by a two-step emulsification procedure and subsequently subjected to temperature changes that caused the oil phase to freeze and thaw while the two aqueous phases remained liquid. Our previous work on individual double-emulsion globules1 demonstrated that crystallizing the oil phase (O) preserves stability, while subsequent thawing triggers coalescence of the droplets of the internal aqueous phase (W1) with the external aqueous phase (W2), termed external coalescence. Activation of this instability mechanism led to instant release of fluorescently tagged bovine serum albumin (fluorescein isothiocyanate (FITC)-BSA) from the W1 droplets and into W2. These results motivated us to apply the proposed temperature-induced globule-breakage mechanism to bulk double emulsions. As expected, no phase separation of the emulsion occurred if stored at temperatures below 18 °C (freezing point of the model oil n-hexadecane), whereas oil thawing readily caused instability. Crucial variables were identified during experimentation, and found to greatly influence the behavior of bulk double emulsions following freeze-thaw cycling. Adjustment of these variables accounted for a more efficient release of the encapsulated protein. PMID:18543998

Gelatin-hydroxypropyl methylcellulose water-in-water emulsions as a new bio-based packaging material.

PubMed

Esteghlal, Sara; Niakosari, Mehrdad; Hosseini, Seyed Mohammad Hashem; Mesbahi, Gholam Reza; Yousefi, Gholam Hossein

2016-05-01

Gelatin and hydroxypropyl methylcellulose (HPMC) are two incompatible and immiscible biopolymers which cannot form homogeneous composite films using usual methods. In this study, to prevent phase separation, gelatin-HPMC water-in-water (W/W) emulsion was utilized to from transparent composite films by entrapment the HPMC dispersed droplets in gelatin continuous network. The physicochemical and mechanical properties of emulsion-based films containing different amounts (5-30%) of dispersed phase were determined and compared with those of individual polymer-based films. Incorporating HPMC into W/W emulsion-based films had no significant effect on the tensile strength. The flexibility of composite films decreased at HPMC concentrations below 20%. The depletion layer at the droplets interface reduced the diffusion of water vapor molecules because of its hydrophobic nature, so the water vapor permeability remained constant. Increasing the HPMC content in the emulsion films increased the swelling and decreased the transparency. The entrapment of HPMC in continuous gelatin phase decreased its solubility. Therefore, W/W emulsions are capable of holding two incompatible polymers alongside each other within a homogeneous film network without weakening the physical properties. Copyright © 2016 Elsevier B.V. All rights reserved.

Wax-incorporated emulsion gel beads of calcium pectinate for intragastric floating drug delivery.

PubMed

Sriamornsak, Pornsak; Asavapichayont, Panida; Nunthanid, Jurairat; Luangtana-Anan, Manee; Limmatvapirat, Sontaya; Piriyaprasarth, Suchada

2008-01-01

The purpose of this study was to prepare wax-incorporated pectin-based emulsion gel beads using a modified emulsion-gelation method. The waxes in pectin-olive oil mixtures containing a model drug, metronidazole, were hot-melted, homogenized and then extruded into calcium chloride solution. The beads formed were separated, washed with distilled water and dried for 12 h. The influence of various types and amounts of wax on floating and drug release behavior of emulsion gel beads of calcium pectinate was investigated. The drug-loaded gel beads were found to float on simulated gastric fluid if the sufficient amount of oil was used. Incorporation of wax into the emulsion gel beads affected the drug release. Water-soluble wax (i.e. polyethylene glycol) increased the drug release while other water-insoluble waxes (i.e. glyceryl monostearate, stearyl alcohol, carnauba wax, spermaceti wax and white wax) significantly retarded the drug release. Different waxes had a slight effect on the drug release. However, the increased amount of incorporated wax in the formulations significantly sustained the drug release while the beads remained floating. The results suggest that wax-incorporated emulsion gel beads could be used as a carrier for intragastric floating drug delivery.

Egg white powder-stabilised multiple (water-in-olive oil-in-water) emulsions as beef fat replacers in model system meat emulsions.

PubMed

Öztürk, Burcu; Urgu, Müge; Serdaroğlu, Meltem

2017-05-01

Today, multiple emulsions are believed to have a considerable application potential in food industry. We aimed to investigate physical, chemical and textural quality characteristics of model system meat emulsions (MSME) in which beef fat (C) was totally replaced by 10% (E-10), 20% (E-20) or 30% (E-30) multiple emulsions (W 1 /O/W 2 ) prepared with olive oil and egg white powder (EWP). Incorporation of W 1 /O/W 2 emulsion resulted in reduced fat (from 11.54% to 4.01%), increased protein content (from 13.66% to 14.74%), and modified fatty acid composition, significantly increasing mono- and polyunsaturated fatty acid content and decreasing saturated fatty acid content. E-20 and E-30 samples had lower jelly and fat separation (5.77% and 5.25%) compared to C and E-10 (9.67% and 8.55%). W 1 /O/W 2 emulsion treatments had higher water-holding capacity (93.96-94.35%) than C samples (91.84%), and also showed the desired storage stability over time. Emulsion stability results showed that E-20 and E-30 samples had lower total expressible fluid (14.05% and 14.53%) and lower total expressible fat (5.06% and 5.33%) compared to C samples (19.13% and 6.09%). Increased concentrations of W 1 /O/W 2 emulsions led to alterations in colour and texture parameters. TBA values of samples were lower in W 1 /O/W 2 emulsion treatments than control treatment during 60 days of storage. Our results indicated that multiple emulsions prepared with olive oil and EWP had promising impacts on reducing fat, modifying the lipid composition and developing both technologically and oxidatively stable meat systems. These are the first findings concerning beef matrix fat replacement with multiple emulsions stabilised by EWP. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Impact of formulation and particle size on stability and immunogenicity of oil-in-water emulsion adjuvants

PubMed Central

Iyer, Vidyashankara; Cayatte, Corinne; Guzman, Bernardo; Schneider-Ohrum, Kirsten; Matuszak, Ryan; Snell, Angie; Rajani, Gaurav Manohar; McCarthy, Michael P; Muralidhara, Bilikallahalli

2015-01-01

Oil-in-water emulsions have gained consideration as vaccine adjuvants in recent years due to their ability to elicit a differentiated immunogenic response compared to traditional aluminum salt adjuvants. Squalene, a cholesterol precursor, is a natural product with immunostimulatory properties, making it an ideal candidate for such oil-in-water emulsions. Particle size is a key parameter of these emulsions and its relationship to stability and adjuvanticity has not been extensively studied. This study evaluates the effect of particle size on the stability and immunogenicity of squalene emulsions. We investigated the effect of formulation parameters such as surfactant concentration on particle size, resulting in particles with average diameter of 80 nm, 100 nm, 150 nm, 200 nm, or 250 nm. Emulsions were exposed to shear and temperature stresses, and stability parameters such as pH, osmolarity, size, and in-depth visual appearance were monitored over time. In addition, adjuvanticity of different particle size was assessed in a mouse model using Respiratory Syncytial Virus Fusion protein (RSV-F) as a model antigen. Temperature dependent phase separation appeared to be the most common route of degradation occurring in the higher particle sizes emulsions. The emulsions below 150 nm size maintained stability at either 5°C or 25°C, and the 80 nm diameter ones showed no measurable changes in size even after one month at 40°C. In vivo studies using the emulsions as an adjuvant with RSV F antigen revealed that superior immunogenicity could be achieved with the 80 nm particle size emulsion. PMID:26090563

A study of the vortex structures around circular cylinder mounted on vertical heated plate

NASA Astrophysics Data System (ADS)

Malah, Hamid; Chumakov, Yurii S.; Levchenya, Alexander M.

2018-05-01

In recent years, studies of natural convection boundary layer interacting with obstacles draw much of attention, because of its practical applications. Pressure gradient resulting from this interaction leads to separation of the boundary layer. The formation of vortex structure around obstacle is characteristic to any kind of convection flow. In this paper, we describe the formation of three-dimensional vortex structure for the case of natural convection flow around the circular cylinder mounted on vertical heated plate. Navier-Stokes equations were used for numerical computations. The results proved the presence of a horseshoe vortex system in the case of natural convection flow as in the forced convection flow.

Strong vortex core pinning and Barkhausen-free magnetization response in thin Permalloy disks induced by implantation of 1 × 10{sup 4} Ga{sup +} ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fani Sani, F., E-mail: fanisani@ualberta.ca, E-mail: mark.freeman@ualberta.ca; Losby, J. E.; Diao, Z.

2014-05-07

Artificial vortex core pinning sites are induced in thin Permalloy disks by point exposure to as few as 10 000 ions from a focused Ga{sup +} beam. These pinning sites yield a first-order change in the magnetization response of the disk. A single site can keep the vortex core pinned over an applied field range comparable to the vortex annihilation field of the unaltered disk. Several widely separated sites can work together to keep the core pinned in one place, while the Barkhausen effect is eliminated from the magnetization curve over a range approaching the saturation moment of the disk.

Flow-separation patterns on symmetric forebodies

NASA Technical Reports Server (NTRS)

Keener, Earl R.

1986-01-01

Flow-visualization studies of ogival, parabolic, and conical forebodies were made in a comprehensive investigation of the various types of flow patterns. Schlieren, vapor-screen, oil-flow, and sublimation flow-visualization tests were conducted over an angle-of-attack range from 0 deg. to 88 deg., over a Reynolds-number range from 0.3X10(6) to 2.0X10(6) (based on base diameter), and over a Mach number range from 0.1 to 2. The principal effects of angle of attack, Reynolds number, and Mach number on the occurrence of vortices, the position of vortex shedding, the principal surface-flow-separation patterns, the magnitude of surface-flow angles, and the extent of laminar and turbulent flow for symmetric, asymmetric, and wake-like flow-separation regimes are presented. It was found that the two-dimensional cylinder analogy was helpful in a qualitative sense in analyzing both the surface-flow patterns and the external flow field. The oil-flow studies showed three types of primary separation patterns at the higher Reynolds numbers owing to the influence of boundary-layer transition. The effect of angle of attack and Reynolds number is to change the axial location of the onset and extent of the primary transitional and turbulent separation regions. Crossflow inflectional-instability vortices were observed on the windward surface at angles of attack from 5 deg. to 55 deg. Their effect is to promote early transition. At low angles of attack, near 10 deg., an unexpected laminar-separation bubble occurs over the forward half of the forebody. At high angles of attack, at which vortex asymmetry occurs, the results support the proposition that the principal cause of vortex asymmetry is the hydrodynamic instability of the inviscid flow field. On the other hand, boundary-layer asymmetries also occur, especially at transitional Reynolds numbers. The position of asymmetric vortex shedding moves forward with increasing angle of attack and with increasing Reynolds number, and moves rearward with increasing Mach number.

Enhancement of vortex induced forces and motion through surface roughness control

DOEpatents

Bernitsas, Michael M [Saline, MI; Raghavan, Kamaldev [Houston, TX

2011-11-01

Roughness is added to the surface of a bluff body in a relative motion with respect to a fluid. The amount, size, and distribution of roughness on the body surface is controlled passively or actively to modify the flow around the body and subsequently the Vortex Induced Forces and Motion (VIFM). The added roughness, when designed and implemented appropriately, affects in a predetermined way the boundary layer, the separation of the boundary layer, the level of turbulence, the wake, the drag and lift forces, and consequently the Vortex Induced Motion (VIM), and the fluid-structure interaction. The goal of surface roughness control is to increase Vortex Induced Forces and Motion. Enhancement is needed in such applications as harnessing of clean and renewable energy from ocean/river currents using the ocean energy converter VIVACE (Vortex Induced Vibration for Aquatic Clean Energy).

A Scanning laser-velocimeter technique for measuring two-dimensional wake-vortex velocity distributions. [Langley Vortex Research Facility

NASA Technical Reports Server (NTRS)

Gartrell, L. R.; Rhodes, D. B.

1980-01-01

A rapid scanning two dimensional laser velocimeter (LV) has been used to measure simultaneously the vortex vertical and axial velocity distributions in the Langley Vortex Research Facility. This system utilized a two dimensional Bragg cell for removing flow direction ambiguity by translating the optical frequency for each velocity component, which was separated by band-pass filters. A rotational scan mechanism provided an incremental rapid scan to compensate for the large displacement of the vortex with time. The data were processed with a digital counter and an on-line minicomputer. Vaporized kerosene (0.5 micron to 5 micron particle sizes) was used for flow visualization and LV scattering centers. The overall measured mean-velocity uncertainity is less than 2 percent. These measurements were obtained from ensemble averaging of individual realizations.

A study of the effectiveness and energy efficiency of ultrasonic emulsification.

PubMed

Li, Wu; Leong, Thomas S H; Ashokkumar, Muthupandian; Martin, Gregory J O

2017-12-20

Three essential experimental parameters in the ultrasonic emulsification process, namely sonication time, acoustic amplitude and processing volume, were individually investigated, theoretically and experimentally, and correlated to the emulsion droplet sizes produced. The results showed that with a decrease in droplet size, two kinetic regions can be separately correlated prior to reaching a steady state droplet size: a fast size reduction region and a steady state transition region. In the fast size reduction region, the power input and sonication time could be correlated to the volume-mean diameter by a power-law relationship, with separate power-law indices of -1.4 and -1.1, respectively. A proportional relationship was found between droplet size and processing volume. The effectiveness and energy efficiency of droplet size reduction was compared between ultrasound and high-pressure homogenisation (HPH) based on both the effective power delivered to the emulsion and the total electric power consumed. Sonication could produce emulsions across a broad range of sizes, while high-pressure homogenisation was able to produce emulsions at the smaller end of the range. For ultrasonication, the energy efficiency was higher at increased power inputs due to more effective droplet breakage at high ultrasound intensities. For HPH the consumed energy efficiency was improved by operating at higher pressures for fewer passes. At the laboratory scale, the ultrasound system required less electrical power than HPH to produce an emulsion of comparable droplet size. The energy efficiency of HPH is greatly improved at large scale, which may also be true for larger scale ultrasonic reactors.

Disintegration and cancer immunotherapy efficacy of a squalane-in-water delivery system emulsified by bioresorbable poly(ethylene glycol)-block-polylactide.

PubMed

Chen, Wei-Lin; Liu, Shih-Jen; Leng, Chih-Hsiang; Chen, Hsin-Wei; Chong, Pele; Huang, Ming-Hsi

2014-02-01

Vaccine adjuvant is conferred on the substance that helps to enhance antigen-specific immune response. Here we investigated the disintegration characteristics and immunotherapy potency of an emulsified delivery system comprising bioresorbable polymer poly(ethylene glycol)-polylactide (PEG-PLA), phosphate buffer saline (PBS), and metabolizable oil squalane. PEG-PLA-stabilized oil-in-water emulsions show good stability at 4 °C and at room temperature. At 37 °C, squalane/PEG-PLA/PBS emulsion with oil/aqueous weight ratio of 7/3 (denominated PELA73) was stable for 6 weeks without phase separation. As PEG-PLA being degraded, 30% of free oil at the surface layer and 10% of water at the bottom disassociated from the PELA73 emulsion were found after 3 months. A MALDI-TOF MS study directly on the DIOS plate enables us to identify low molecular weight components released during degradation. Our results confirm the loss of PLA moiety of the emulsifier PEG-PLA directly affected the stability of PEG-PLA-stabilized emulsion, leading to emulsion disintegration and squalane/water phase separation. As adjuvant for cancer immunotherapeutic use, an HPV16 E7 peptide antigen formulated with PELA73 plus immunostimulatory CpG molecules could strongly enhance antigen-specific T-cell responses as well as anti-tumor ability with respected to non-formulated or Alum-formulated peptide. Accordingly, these advances may be a potential immunoregulatory strategy in manipulating the immune responses induced by tumor-associated antigens. Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.

Separated Flow Control with Actuated Membrane Wings

NASA Astrophysics Data System (ADS)

Bohnker, Jillian; Breuer, Kenneth

2017-11-01

By perturbing shear layer instabilities, some level of control over highly separated flows can be established, as has been demonstrated on rigid wings using synthetic jet actuators or acoustic excitation. Here, we demonstrate similar phenomena using sinusoidal actuation of a dielectric membrane wing. The effect of actuation on lift is examined as a function of freestream velocity (5-25 m/s), angle of attack (10°-40°), and actuation frequency (0.1

Novel aqueous oil-in-water emulsions containing extracts of natural coniferous resins are strongly antimicrobial against enterobacteria, staphylococci and yeasts, as well as on bacterial biofilms.

PubMed

Haapakorva, E; Holmbom, T; von Wright, A

2018-01-01

The aim of this study was to examine the antimicrobial properties of novel aqueous natural rapeseed oil/saline emulsions containing different soluble components of spruce resin. The composition of aqueous resin emulsions was analysed by GC-MS and their antimicrobial properties were studied with challenge tests and with turbidometric assays. The emulsions were strongly antimicrobial against common Gram-positive and Gram-negative bacteria (including MRSA) as well as common yeasts. Furthermore, they inhibited the biofilm formation and eradicated the microbial biofilms on tested microbes. Characteristic for the emulsions was the presence of oxidized resin acids. Other main components present in emulsions, such as lignans and coumaric acids, were not antimicrobial, when tested separately. The results indicated that the oxidized resin acids were the antimicrobial components in the emulsions. Also, there appears to be a stoichiometric relationship between the number of resin acid molecules and the number microbe cells in the antimicrobial action. The fact that these solutions do not contain abietic acid, which is the main allergenic compound in resins, suggests that these solutions would be suitable, well-tolerated antimicrobials for various medical applications. The aqueous formulation will also allow the expansion of the use of these emulsions in from medical applications to the food preservatives and disinfectants. © 2017 The Authors. Journal of Applied Microbiology published by John Wiley & Sons Ltd on behalf of the Society for Applied Microbiology.

Several examples where turbulence models fail in inlet flow field analysis

NASA Technical Reports Server (NTRS)

Anderson, Bernhard H.

1993-01-01

Computational uncertainties in turbulence modeling for three dimensional inlet flow fields include flows approaching separation, strength of secondary flow field, three dimensional flow predictions of vortex liftoff, and influence of vortex-boundary layer interactions; computational uncertainties in vortex generator modeling include representation of generator vorticity field and the relationship between generator and vorticity field. The objectives of the inlet flow field studies presented in this document are to advance the understanding, prediction, and control of intake distortion and to study the basic interactions that influence this design problem.

An airborne system for vortex flow visualization on the F-18 high-alpha research vehicle

NASA Technical Reports Server (NTRS)

Curry, Robert E.; Richwine, David M.

1988-01-01

A flow visualization system for the F-18 high-alpha research vehicle is described which allows direct observation of the separated vortex flows over a wide range of flight conditions. The system consists of a smoke generator system, on-board photographic and video systems, and instrumentation. In the present concept, smoke is entrained into the low-pressure vortex core, and vortice breakdown is indicated by a rapid diffusion of the smoke. The resulting pattern is observed using photographic and video images and is correlated with measured flight conditions.

Stripping ethanol from ethanol-blended fuels for use in NO.sub.x SCR

DOEpatents

Kass, Michael Delos [Oak Ridge, TN; Graves, Ronald Lee [Knoxville, TN; Storey, John Morse Elliot [Oak Ridge, TN; Lewis, Sr., Samuel Arthur; Sluder, Charles Scott [Knoxville, TN; Thomas, John Foster [Powell, TN

2007-08-21

A method to use diesel fuel alchohol micro emulsions (E-diesel) to provide a source of reductant to lower NO.sub.x emissions using selective catalytic reduction. Ethanol is stripped from the micro emulsion and entered into the exhaust gasses upstream of the reducing catalyst. The method allows diesel (and other lean-burn) engines to meet new, lower emission standards without having to carry separate fuel and reductant tanks.

Wake Vortex Transport and Decay in Ground Effect: Vortex Linking with the Ground

NASA Technical Reports Server (NTRS)

Proctor, Fred H.; Hamilton, David W.; Han, Jongil

2000-01-01

Numerical simulations are carried out with a three-dimensional Large-Eddy Simulation (LES) model to explore the sensitivity of vortex decay and transport in ground effect (IGE). The vortex decay rates are found to be strongly enhanced following maximum descent into ground effect. The nondimensional decay rate is found to be insensitive to the initial values of circulation, height, and vortex separation. The information gained from these simulations is used to construct a simple decay relationship. This relationship compares well with observed data from an IGE case study. Similarly, a relationship for lateral drift due to ground effect is constructed from the LES data. In the second part of this paper, vortex linking with the ground is investigated. Our numerical simulations of wake vortices for IGE show that a vortex may link with its image beneath the ground, if the intensity of the ambient turbulence is moderate to high. This linking with the ground (which is observed in real cases)gives the appearance of a vortex tube that bends to become vertically oriented and which terminates at the ground. From the simulations conducted, the linking time for vortices in the free atmosphere; i.e., a function of ambient turbulence intensity.

Measurements of a turbulent horseshoe vortex formed around a cylinder

NASA Technical Reports Server (NTRS)

Eckerle, W. A.; Langston, L. S.

1986-01-01

An experimental investigation was conducted to characterize a symmetrical horseshoe vortex system in front of and around a single large-diameter right cylinder centered between the sidewalls of a wind tunnel. Surface flow visualization and surface static pressure measurements as well as extensive mean velocity and pressure measurements in and around the vortex system were acquired. The results lend new insight into the formation and development of the vortex system. Contrary to what has been assumed previously, a strong vortex was not identified in the streamwise plane of symmetry, but started a significant angular distance away from it. Rather than the multiple vortex systems reported by others, only a single primary vortex and saddle point were found. The scale of the separation process at the saddle point was much smaller than the scale of the approaching boundary layer thickness. Results of the present study not only shed light on such phenomena as the nonsymmetrical endwall flow in axial turbomachinery but can also be used as a test case for three-dimensional computational fluid mechanics computer codes.

Turbulence Climatology at Dallas/Ft.Worth (DFW) Airport: Implications for a Departure Wake Vortex Spacing System

NASA Technical Reports Server (NTRS)

Perras, G. H.; Dasey, T. J.

2000-01-01

Potential adaptive wake vortex spacing systems may need to rely on wake vortex decay rather than wake vortex transport in reducing wake separations. A wake vortex takeoff-spacing system in particular will need to rely on wake decay. Ambient turbulence is the primary influence on wake decay away from the ground. This study evaluated 18 months of ambient turbulence measurements at Dallas/Ft. Worth (DFW) Airport. The measurements show minor variation in the turbulence levels at various times of the year or times of the day for time periods when a departure system could be used. Arrival system operation was also examined, and a slightly lower overall turbulence level was found as compared to departure system benefit periods. The Sarpkaya model, a validated model of wake vortex behavior, was applied to various turbulence levels and compared to the DFW turbulence statistics. The results show that wake vortices from heavy aircraft on takeoff should dissipate within one minute for the majority of the time and will rarely last two minutes. These results will need to be verified by wake vortex measurements on departure.

Bond Graph Modeling and Validation of an Energy Regenerative System for Emulsion Pump Tests

PubMed Central

Li, Yilei; Zhu, Zhencai; Chen, Guoan

2014-01-01

The test system for emulsion pump is facing serious challenges due to its huge energy consumption and waste nowadays. To settle this energy issue, a novel energy regenerative system (ERS) for emulsion pump tests is briefly introduced at first. Modeling such an ERS of multienergy domains needs a unified and systematic approach. Bond graph modeling is well suited for this task. The bond graph model of this ERS is developed by first considering the separate components before assembling them together and so is the state-space equation. Both numerical simulation and experiments are carried out to validate the bond graph model of this ERS. Moreover the simulation and experiments results show that this ERS not only satisfies the test requirements, but also could save at least 25% of energy consumption as compared to the original test system, demonstrating that it is a promising method of energy regeneration for emulsion pump tests. PMID:24967428

Creaming enhancement in a liter scale ultrasonic reactor at selected transducer configurations and frequencies.

PubMed

Juliano, Pablo; Temmel, Sandra; Rout, Manoj; Swiergon, Piotr; Mawson, Raymond; Knoerzer, Kai

2013-01-01

Recent research has shown that high frequency ultrasound (0.4-3 MHz), can enhance milkfat separation in small scale systems able to treat only a few milliliters of sample. In this work, the effect of ultrasonic standing waves on milkfat creaming was studied in a 6L reactor and the influence of different frequencies and transducer configurations in direct contact with the fluid was investigated. A recombined coarse milk emulsion with fat globules stained with oil-red-O dye was selected for the separation trials. Runs were performed with one or two transducers placed in vertical (parallel or perpendicular) and horizontal positions (at the reactor base) at 0.4, 1 and/or 2 MHz (specific energy 8.5 ± 0.6 kJ/kg per transducer). Creaming behavior was assessed by measuring the thickness of the separated cream layer. Other methods supporting this assessment included the measurement of fat content, backscattering, particle size distribution, and microscopy of samples taken at the bottom and top of the reactor. Most efficient creaming was found after treatment at 0.4 MHz in single and double vertical transducer configurations. Among these configurations, a higher separation rate was obtained when sonicating at 0.4 MHz in a vertical perpendicular double transducer setup. The horizontal transducer configuration promoted creaming at 2 MHz only. Fat globule size increase was observed when creaming occurred. This research highlights the potential for enhanced separation of milkfat in larger scale systems from selected transducer configurations in contact with a dairy emulsion, or emulsion splitting in general. Copyright © 2012 Elsevier B.V. All rights reserved.

Experimental Investigation of Inter-Blade Vortices in a Model Francis Turbine

NASA Astrophysics Data System (ADS)

LIU, Demin; LIU, Xiaobing; ZHAO, Yongzhi

2017-07-01

The inter-blade vortex in a Francis turbine becomes one of the main hydraulic factors that are likely to cause blade erosion at deep part load operating conditions. However, the causes and the mechanism of inter-blade vortex are still under investigation according to present researches. Thus the causes of inter-blade vortex and the effect of different hydraulic parameters on the inter-blade vortex are investigated experimentally. The whole life cycle of the inter-blade vortex is observed by a high speed camera. The test results illustrate the whole life cycle of the inter-blade vortex from generation to separation and even to fading. It is observed that the inter-blade vortex becomes stronger with the decreasing of flow and head, which leads to pressure fluctuation. Meanwhile, the pressure fluctuations in the vane-less area and the draft tube section become stronger when inter-blade vortices exist in the blade channel. The turbine will be damaged if operating in the inter-blade vortex zone, so its operating range must be far away from that zone. This paper reveals the main cause of the inter-blade vortex which is the larger incidence angle between the inflow angle and the blade angle on the leading edge of the runner at deep part load operating conditions.

Combined action of transverse oscillations and uniform cross-flow on vortex formation and pattern of a circular cylinder

NASA Astrophysics Data System (ADS)

Lam, K. M.; Liu, P.; Hu, J. C.

2010-07-01

This paper attempts to study the roles of lateral cylinder oscillations and a uniform cross-flow in the vortex formation and wake modes of an oscillating circular cylinder. A circular cylinder is given lateral oscillations of varying amplitudes (between 0.28 and 1.42 cylinder-diameters) in a slow uniform flow stream (Reynolds number=284) to produce the 2S, 2P and P+S wake modes. Detailed flow information is obtained with time-resolved particle-image velocimetry and the phase-locked averaging techniques. In the 2S and 2P mode, the flow speeds relative to the cylinder movement are less than the uniform flow velocity and it is found that initial formation of a vortex is caused by shear-layer separation of the uniform flow on the cylinder. Subsequent development of the shear-layer vortices is affected by the lateral cylinder movement. At small cylinder oscillation amplitudes, vortices are shed in synchronization with the cylinder movement, resulting in the 2S mode. The 2P mode occurs at larger cylinder oscillation amplitudes at which each shear-layer vortex is found to undergo intense stretching and eventual bifurcation into two separate vortices. The P+S mode occurs when the cylinder moving speeds are, for most of the time, higher than the speed of the uniform flow. These situations are found at fast and large-amplitude cylinder oscillations in which the flow relative to the cylinder movement takes over the uniform flow in governing the initial vortex formation. The formation stages of vortices from the cylinder are found to bear close resemblance to those of a vortex street pattern of a cylinder oscillating in an otherwise quiescent fluid at Keulegan-Carpenter numbers around 16. Vortices in the inclined vortex street pattern so formed are then convected downstream by the uniform flow as the vortex pairs in the 2P mode.

Emulsifying properties of acidic subunits of soy 11S globulin.

PubMed

Liu, M; Lee, D S; Damodaran, S

1999-12-01

The emulsifying properties of the acidic subunits (AS11S) isolated from soy glycinin (11S) have been studied. The isolated AS11S existed in solution mainly as a dimer species. Circular dichroic analysis indicated only a slight increase in aperiodic structure and no significant difference in beta-sheet structure when compared with those of soy 11S. At similar experimental conditions, the emulsifying properties of AS11S were superior to those of soy 11S and heat-denatured 11S. Emulsions prepared with 1% AS11S remained very stable without any visible oil separation for more than a month under gentle agitating conditions, whereas those prepared with 1% 11S collapsed and separated into phases within 2-3 days. The AS11S-stabilized emulsions were very stable below 0.15 M ionic strength. Studies on the rate of adsorption and surface tension reduction at the air-water interface showed that AS11S was significantly more surface active than soy 11S. It is proposed that, because the mass fraction of acidic subunits in soy 11S is approximately 60% and it is relatively easy to separate the acidic subunits from soy 11S, it may be industrially feasible to develop an economical process to isolate functional acidic subunits for use in emulsion-based food products.

Analytical investigation of aerodynamic characteristics of highly swept wings with separated flow

NASA Technical Reports Server (NTRS)

Reddy, C. S.

1980-01-01

Many modern aircraft designed for supersonic speeds employ highly swept-back and low-aspect-ratio wings with sharp or thin edges. Flow separation occurs near the leading and tip edges of such wings at moderate to high angles of attack. Attempts have been made over the years to develop analytical methods for predicting the aerodynamic characteristics of such aircraft. Before any method can really be useful, it must be tested against a standard set of data to determine its capabilities and limitations. The present work undertakes such an investigation. Three methods are considered: the free-vortex-sheet method (Weber et al., 1975), the vortex-lattice method with suction analogy (Lamar and Gloss, 1975), and the quasi-vortex lattice method of Mehrotra (1977). Both flat and cambered wings of different configurations, for which experimental data are available, are studied and comparisons made.

Onsager Vortex Formation in Two-component Bose-Einstein Condensates

NASA Astrophysics Data System (ADS)

Han, Junsik; Tsubota, Makoto

2018-06-01

We numerically study the dynamics of quantized vortices in two-dimensional two-component Bose-Einstein condensates (BECs) trapped by a box potential. For one-component BECs in a box potential, it is known that quantized vortices form Onsager vortices, which are clusters of same-sign vortices. We confirm that the vortices of the two components spatially separate from each other — even for miscible two-component BECs — suppressing the formation of Onsager vortices. This phenomenon is caused by the repulsive interaction between vortices belonging to different components, hence, suggesting a new possibility for vortex phase separation.

On the ejection-induced instability in Navier-Stokes solutions of unsteady separation.

PubMed

Obabko, Aleksandr V; Cassel, Kevin W

2005-05-15

Numerical solutions of the flow induced by a thick-core vortex have been obtained using the unsteady, two-dimensional Navier-Stokes equations. The presence of the vortex causes an adverse pressure gradient along the surface, which leads to unsteady separation. The calculations by Brinckman and Walker for a similar flow identify a possible instability, purported to be an inviscid Rayleigh instability, in the region where ejection of near-wall vorticity occurs during the unsteady separation process. In results for a range of Reynolds numbers in the present investigation, the oscillations are also found to occur. However, they can be eliminated with increased grid resolution. Despite this behaviour, the instability may be physical but requires a sufficient amplitude of disturbances to be realized.

Effect of Phytosterols on the Crystallization Behavior of Oil-in-Water Milk Fat Emulsions.

PubMed

Zychowski, Lisa M; Logan, Amy; Augustin, Mary Ann; Kelly, Alan L; Zabara, Alexandru; O'Mahony, James A; Conn, Charlotte E; Auty, Mark A E

2016-08-31

Milk has been used commercially as a carrier for phytosterols, but there is limited knowledge on the effect of added plant sterols on the properties of the system. In this study, phytosterols dispersed in milk fat at a level of 0.3 or 0.6% were homogenized with an aqueous dispersion of whey protein isolate (WPI). The particle size, morphology, ζ-potential, and stability of the emulsions were investigated. Emulsion crystallization properties were examined through the use of differential scanning calorimetry (DSC) and Synchrotron X-ray scattering at both small and wide angles. Phytosterol enrichment influenced the particle size and physical appearance of the emulsion droplets, but did not affect the stability or charge of the dispersed particles. DSC data demonstrated that, at the higher level of phytosterol addition, crystallization of milk fat was delayed, whereas, at the lower level, phytosterol enrichment induced nucleation and emulsion crystallization. These differences were attributed to the formation of separate phytosterol crystals within the emulsions at the high phytosterol concentration, as characterized by Synchrotron X-ray measurements. X-ray scattering patterns demonstrated the ability of the phytosterol to integrate within the milk fat triacylglycerol matrix, with a concomitant increase in longitudinal packing and system disorder. Understanding the consequences of adding phytosterols, on the physical and crystalline behavior of emulsions may enable the functional food industry to design more physically and chemically stable products.

Feasibility of low frequency ultrasound for water removal from crude oil emulsions.

PubMed

Antes, Fabiane G; Diehl, Liange O; Pereira, Juliana S F; Guimarães, Regina C L; Guarnieri, Ricardo A; Ferreira, Bianca M S; Dressler, Valderi L; Flores, Erico M M

2015-07-01

The feasibility of indirect application of low frequency ultrasound for demulsification of crude oil was investigated without using chemical demulsifiers. Experiments were performed in an ultrasonic bath with frequency of 35 kHz. Synthetic emulsions with water content of 12%, 35% and 50% and median of droplet size distribution (DSD), median D(0.5), of 5, 10 and 25 μm were prepared from crude oil with API density of 19 (heavy crude oil) and submitted to the proposed ultrasound-assisted demulsification procedure. Experimental conditions as temperature, time of exposition to ultrasound and ultrasonic power were evaluated. Separation of water from crude oil emulsion was observed for all emulsions investigated. Demulsification efficiency up to 65% was obtained for emulsion with 50% of water content and DSD of 10 μm. Higher efficiency of demulsification was achieved using US temperature of 45 °C and ultrasound power of 160 W by 15 min. Results obtained in this study showed that ultrasound could be considered a promising technology for industrial crude oil treatment and respective water removal. Copyright © 2015 Elsevier B.V. All rights reserved.

Enzymatically structured emulsions in simulated gastrointestinal environment: impact on interfacial proteolysis and diffusion in intestinal mucus.

PubMed

Macierzanka, Adam; Böttger, Franziska; Rigby, Neil M; Lille, Martina; Poutanen, Kaisa; Mills, E N Clare; Mackie, Alan R

2012-12-18

Fundamental knowledge of physicochemical interactions in the gastrointestinal environment is required in order to support rational designing of protein-stabilized colloidal food and pharmaceutical delivery systems with controlled behavior. In this paper, we report on the colloidal behavior of emulsions stabilized with the milk protein sodium caseinate (Na-Cas), and exposed to conditions simulating the human upper gastrointestinal tract. In particular, we looked at how the kinetics of proteolysis was affected by adsorption to an oil-water interface in emulsion and whether the proteolysis and the emulsion stability could be manipulated by enzymatic structuring of the interface. After cross-linking with the enzyme transglutaminase, the protein was digested with use of an in vitro model of gastro-duodenal proteolysis in the presence or absence of physiologically relevant surfactants (phosphatidylcholine, PC; bile salts, BS). Significant differences were found between the rates of digestion of Na-Cas cross-linked in emulsion (adsorbed protein) and in solution. In emulsion, the digestion of a population of polypeptides of M(r) ca. 50-100 kDa was significantly retarded through the gastric digestion. The persistent interfacial polypeptides maintained the original emulsion droplet size and prevented the system from phase separating. Rapid pepsinolysis of adsorbed, non-cross-linked Na-Cas and its displacement by PC led to emulsion destabilization. These results suggest that structuring of emulsions by enzymatic cross-linking of the interfacial protein may affect the phase behavior of emulsion in the stomach and the gastric digestion rate in vivo. Measurements of ζ-potential revealed that BS displaced the remaining protein from the oil droplets during the simulated duodenal phase of digestion. Diffusion of the postdigestion emulsion droplets through ex vivo porcine intestinal mucus was only significant in the presence of BS due to the high negative charge these biosurfactants imparted to the droplets. This implies that the electrostatic repulsion produced can prevent the droplets from being trapped by the mucus matrix and facilitate their transport across the small intestine mucosal barrier.

Eco-Friendly Superwetting Material for Highly Effective Separations of Oil/Water Mixtures and Oil-in-Water Emulsions.

PubMed

Wang, Chih-Feng; Yang, Sheng-Yi; Kuo, Shiao-Wei

2017-02-20

Because the treatment of oily wastewater, generated from many industrial processes, has become an increasing environmental concern, the search continues for simple, inexpensive, eco-friendly, and readily scalable processes for fabricating novel materials capable of effective oil/water separation. In this study we prepared an eco-friendly superhydrophilic and underwater superoleophobic polyvinylpyrrolidone (PVP)-modified cotton that mediated extremely efficient separations of mixtures of oil/water and oil/corrosive solutions. This PVP-modified cotton exhibited excellent antifouling properties and could be used to separate oil/water mixtures continuously for up to 20 h. Moreover, the compressed PVP-modified cotton could separate both surfactant-free and -stabilized oil-in-water emulsions with fluxes of up to 23,500 L m -2 h -1 bar -1 -a level one to two orders of magnitude higher than that possible when using traditional ultrafiltration membranes having similar rejection properties. The high performance of our PVP-modified cotton and its green, low-energy, cost-effective preparation suggest its great potential for practical applications.

Eco-Friendly Superwetting Material for Highly Effective Separations of Oil/Water Mixtures and Oil-in-Water Emulsions

NASA Astrophysics Data System (ADS)

Wang, Chih-Feng; Yang, Sheng-Yi; Kuo, Shiao-Wei

2017-02-01

Because the treatment of oily wastewater, generated from many industrial processes, has become an increasing environmental concern, the search continues for simple, inexpensive, eco-friendly, and readily scalable processes for fabricating novel materials capable of effective oil/water separation. In this study we prepared an eco-friendly superhydrophilic and underwater superoleophobic polyvinylpyrrolidone (PVP)-modified cotton that mediated extremely efficient separations of mixtures of oil/water and oil/corrosive solutions. This PVP-modified cotton exhibited excellent antifouling properties and could be used to separate oil/water mixtures continuously for up to 20 h. Moreover, the compressed PVP-modified cotton could separate both surfactant-free and -stabilized oil-in-water emulsions with fluxes of up to 23,500 L m-2 h-1 bar-1—a level one to two orders of magnitude higher than that possible when using traditional ultrafiltration membranes having similar rejection properties. The high performance of our PVP-modified cotton and its green, low-energy, cost-effective preparation suggest its great potential for practical applications.

Eco-Friendly Superwetting Material for Highly Effective Separations of Oil/Water Mixtures and Oil-in-Water Emulsions

PubMed Central

Wang, Chih-Feng; Yang, Sheng-Yi; Kuo, Shiao-Wei

2017-01-01

Because the treatment of oily wastewater, generated from many industrial processes, has become an increasing environmental concern, the search continues for simple, inexpensive, eco-friendly, and readily scalable processes for fabricating novel materials capable of effective oil/water separation. In this study we prepared an eco-friendly superhydrophilic and underwater superoleophobic polyvinylpyrrolidone (PVP)-modified cotton that mediated extremely efficient separations of mixtures of oil/water and oil/corrosive solutions. This PVP-modified cotton exhibited excellent antifouling properties and could be used to separate oil/water mixtures continuously for up to 20 h. Moreover, the compressed PVP-modified cotton could separate both surfactant-free and -stabilized oil-in-water emulsions with fluxes of up to 23,500 L m−2 h−1 bar−1—a level one to two orders of magnitude higher than that possible when using traditional ultrafiltration membranes having similar rejection properties. The high performance of our PVP-modified cotton and its green, low-energy, cost-effective preparation suggest its great potential for practical applications. PMID:28216617

Computational study of the vortex path variation with the VG height

NASA Astrophysics Data System (ADS)

Fernández-Gámiz, U.; Zamorano, G.; Zulueta, E.

2014-06-01

An extensive range of conventional, vane-type, passive vortex generators (VGs) are in use for successful applications of flow separation control. In most cases, the VG height is designed with the same thickness as the local boundary layer at the VG position. However, in some applications, these conventional VGs may produce excess residual drag. The so-called low-profile VGs can reduce the parasitic drag associated to this kind of passive control devices. As suggested by many authors, low-profile VGs can provide enough momentum transfer over a region several times their own height for effective flow-separation control with much lower drag. The main objective of this work is to study the variation of the path and the development of the primary vortex generated by a rectangular VG mounted on a flat plate with five different device heights h = δ, h1 = 0.8δ, h2 = 0.6δ, h3 = 0.4δ and h4 = 0.25m, where 5 is the local boundary layer thickness. For this purpose, computational simulations have been carried out at Reynolds number Re = 1350 based on the height of the conventional VG h = 0.25m with the angle of attack of the vane to the oncoming flow β = 18.5°. The results show that the VG scaling significantly affects the vortex trajectory and the peak vorticity generated by the primary vortex.

Theoretical study of aerodynamic characteristics of wings having vortex flow

NASA Technical Reports Server (NTRS)

Reddy, C. S.

1979-01-01

The aerodynamic characteristics of slender wings having separation induced vortex flows are investigated by employing three different computer codes--free vortex sheet, quasi vortex lattice, and suction analogy methods. Their capabilities and limitations are examined, and modifications are discussed. Flat wings of different configurations: arrow, delta, and diamond shapes, as well as cambered delta wings, are studied. The effect of notch ratio on the load distributions and the longitudinal characteristics of a family of arrow and diamond wings is explored. The sectional lift coefficients and the accumulated span loadings are determined for an arrow wing and are seen to be unusual in comparison with the attached flow results. The theoretically predicted results are compared with the existing experimental values.

Analytical and numerical performance models of a Heisenberg Vortex Tube

NASA Astrophysics Data System (ADS)

Bunge, C. D.; Cavender, K. A.; Matveev, K. I.; Leachman, J. W.

2017-12-01

Analytical and numerical investigations of a Heisenberg Vortex Tube (HVT) are performed to estimate the cooling potential with cryogenic hydrogen. The Ranque-Hilsch Vortex Tube (RHVT) is a device that tangentially injects a compressed fluid stream into a cylindrical geometry to promote enthalpy streaming and temperature separation between inner and outer flows. The HVT is the result of lining the inside of a RHVT with a hydrogen catalyst. This is the first concept to utilize the endothermic heat of para-orthohydrogen conversion to aid primary cooling. A review of 1st order vortex tube models available in the literature is presented and adapted to accommodate cryogenic hydrogen properties. These first order model predictions are compared with 2-D axisymmetric Computational Fluid Dynamics (CFD) simulations.

Numerical Study of Wake Vortex Behavior in Turbulent Domains with Ambient Stratification

NASA Technical Reports Server (NTRS)

Switzer, George F.; Proctor, Fred H.

2000-01-01

A three-dimensional large eddy simulation model is used to investigate the sensitivity of ambient stratification with turbulence on the behavior of aircraft wake vortices. Modeled ambient turbulence levels range from very weak to moderate, and stratification levels range from strongly stable to unstable. The results of profound significance from this study are: 1) very little sensitivity between vortex linking time and the level of stratification, 2) the mean vortex separation remained nearly constant regardless of stratification and turbulence (at least prior to linking), 3) the wake vortices did not rise regardless of the level of stratification, and 4) for very strong stratification, the vortex stopped descending and quickly dissipated even before vortex linking could occur. These results are supported by experimental data and are contrary to conclusions from other numerical studies that assume laminar flow and/or relatively-low Reynolds numbers.

Wake Vortex Advisory System (WakeVAS) Concept of Operations

NASA Technical Reports Server (NTRS)

Rutishauser, David; Lohr, Gary; Hamilton, David; Powers, Robert; McKissick, Burnell; Adams, Catherine; Norris, Edward

2003-01-01

NASA Langley Research Center has a long history of aircraft wake vortex research, with the most recent accomplishment of demonstrating the Aircraft VOrtex Spacing System (AVOSS) at Dallas/Forth Worth International Airport in July 2000. The AVOSS was a concept for an integration of technologies applied to providing dynamic wake-safe reduced spacing for single runway arrivals, as compared to current separation standards applied during instrument approaches. AVOSS included state-of-the-art weather sensors, wake sensors, and a wake behavior prediction algorithm. Using real-time data AVOSS averaged a 6% potential throughput increase over current standards. This report describes a Concept of Operations for applying the technologies demonstrated in the AVOSS to a variety of terminal operations to mitigate wake vortex capacity constraints. A discussion of the technological issues and open research questions that must be addressed to design a Wake Vortex Advisory System (WakeVAS) is included.

Observation of self-excited acoustic vortices in defect-mediated dust acoustic wave turbulence.

PubMed

Tsai, Ya-Yi; I, Lin

2014-07-01

Using the self-excited dust acoustic wave as a platform, we demonstrate experimental observation of self-excited fluctuating acoustic vortex pairs with ± 1 topological charges through spontaneous waveform undulation in defect-mediated turbulence for three-dimensional traveling nonlinear longitudinal waves. The acoustic vortex pair has helical waveforms with opposite chirality around the low-density hole filament pair in xyt space (the xy plane is the plane normal to the wave propagation direction). It is generated through ruptures of sequential crest surfaces and reconnections with their trailing ruptured crest surfaces. The initial rupture is originated from the amplitude reduction induced by the formation of the kinked wave crest strip with strong stretching through the undulation instability. Increasing rupture causes the separation of the acoustic vortex pair after generation. A similar reverse process is followed for the acoustic vortex annihilating with the opposite-charged acoustic vortex from the same or another pair generation.

Effect of intragastric acid stability of fat emulsions on gastric emptying, plasma lipid profile and postprandial satiety.

PubMed

Marciani, Luca; Faulks, Richard; Wickham, Martin S J; Bush, Debbie; Pick, Barbara; Wright, Jeff; Cox, Eleanor F; Fillery-Travis, Annette; Gowland, Penny A; Spiller, Robin C

2009-03-01

Fat is often included in common foods as an emulsion of dispersed oil droplets to enhance the organoleptic quality and stability. The intragastric acid stability of emulsified fat may impact on gastric emptying, satiety and plasma lipid absorption. The aim of the present study was to investigate whether, compared with an acid-unstable emulsion, an acid-stable fat emulsion would empty from the stomach more slowly, cause more rapid plasma lipid absorption and cause greater satiety. Eleven healthy male volunteers received on two separate occasions 500 ml of 15 % (w/w) [13C]palmitate-enriched olive oil-in-water emulsion meals which were either stable or unstable in the acid gastric environment. MRI was used to measure gastric emptying and the intragastric oil fraction of the meals. Blood sampling was used to measure plasma lipids and visual analogue scales were used to assess satiety. The acid-unstable fat emulsion broke and rapidly layered in the stomach. Gastric emptying of meal volume was slower for the acid-stable fat emulsion (P < 0.0001; two-way ANOVA). The rate of energy delivery of fat from the stomach to the duodenum was not different up to t = 110 min. The acid-stable emulsion induced increased fullness (P < 0.05), decreased hunger (P < 0.0002), decreased appetite (P < 0.0001) and increased the concentration of palmitic acid tracer in the chylomicron fraction (P < 0.04). This shows that it is possible to delay gastric emptying and increase satiety by stabilising the intragastric distribution of fat emulsions against the gastric acid environment. This could have implications for the design of novel foods.

A Three-Dimensional CFD Investigation of Secondary Flow in an Accelerating, 90 deg Elbow

NASA Technical Reports Server (NTRS)

Cavicchi, Richard H.

2001-01-01

NASA Glenn Research Center has recently applied the WIND National Code flow solver to an accelerating elbow with a 90 deg. bend to reveal aspects of secondary flow. This elbow was designed by NACA in the early 1950's such that flow separation would be avoided. Experimental testing was also done at that time. The current three dimensional CFD investigation shows that separation has indeed been avoided. Using its three-dimensional capability, this investigation provides various viewpoints in several planes that display the inception, development, and final location of a passage vortex. Its shape first becomes discernible as a vortex near the exit of the bend. This rendition of the exit passage vortex compares well with that found in the experiments. The viewpoints show that the passage vortex settles on the suction surface at the exit about one-third of the distance between the plane wall and midspan. Furthermore, it projects into the mainstream to about one-third of the channel width. Of several turbulence models used in this investigation, the Spalart Alimaras, Baldwin Lomax, and SST (Shear Stress Transport) models were by far the most successful in matching the experiments.

A colloidal assembly approach to synthesize magnetic porous composite nanoclusters for efficient protein adsorption

NASA Astrophysics Data System (ADS)

Yang, Qi; Lan, Fang; Yi, Qiangying; Wu, Yao; Gu, Zhongwei

2015-10-01

A combination strategy of the inverse emulsion crosslinking approach and the colloidal assembly technique is first proposed to synthesize Fe3O4/histidine composite nanoclusters as new-type magnetic porous nanomaterials. The nanoclusters possess uniform morphology, high magnetic content and excellent protein adsorption capacity, exhibiting their great potential for bio-separation.A combination strategy of the inverse emulsion crosslinking approach and the colloidal assembly technique is first proposed to synthesize Fe3O4/histidine composite nanoclusters as new-type magnetic porous nanomaterials. The nanoclusters possess uniform morphology, high magnetic content and excellent protein adsorption capacity, exhibiting their great potential for bio-separation. Electronic supplementary information (ESI) available: Experimental details. See DOI: 10.1039/c5nr05800g

Polystyrene/Fe3O4 magnetic emulsion and nanocomposite prepared by ultrasonically initiated miniemulsion polymerization.

PubMed

Qiu, Guihua; Wang, Qi; Wang, Chao; Lau, Willie; Guo, Yili

2007-01-01

Ultrasonically initiated miniemulsion polymerization of styrene in the presence of Fe3O4 nanoparticles was successfully employed to prepare polystyrene (PS)/Fe3O4 magnetic emulsion and nanocomposite. The effects of Fe3O4 nanoparticles on miniemulsion polymerization process, the structure, morphology and properties of PS/Fe3O4 nanocomposite were investigated. The increase in the amount of Fe3O4 nanoparticles drastically increases the polymerization rate due to that Fe3O4 nanoparticles increase the number of radicals and the cavitation bubbles. Polymerization kinetics of ultrasonically initiated miniemulsion polymerization is similar to that of conventional miniemulsion polymerization. PS/Fe3O4 magnetic emulsion consists of two types of particles: latex particles with Fe3O4 nanoparticles and latex particles with no encapsulated Fe3O4 nanoparticles. Fe3O4 nanoparticles lower the molecular weight of PS and broaden the molecular weight and particle size distribution. Thermal stability of PS/Fe3O4 nanocomposite increases with the increase in Fe3O4 content. PS/Fe3O4 emulsion and nanocomposite exhibit magnetic properties. PS/Fe3O4 magnetic particles can be separated from the magnetic emulsion by an external magnetic field and redispersed into the emulsion with agitation.

The Wake Vortex Prediction and Monitoring System WSVBS

NASA Astrophysics Data System (ADS)

Gerz, T.; Holzäpfel, F.

2009-09-01

Design and performance of the Wake Vortex Prediction and Monitoring System WSVBS are described. The WSVBS has been developed to tactically increase airport capacity for approach and landing on closely-spaced parallel runways. It is thought to dynamically adjust aircraft separations dependent on weather conditions and the resulting wake vortex behaviour without compromising safety. The WSVBS consists of components that consider meteorological conditions, aircraft glide path adherence, aircraft parameter combinations representing aircraft weight categories, the resulting wake-vortex behaviour, the surrounding safety areas, wake vortex monitoring, and the integration of the predictions into the arrival manager. The WSVBS has been designed and applied to Frankfurt Airport. However, its components are generic and can well be adjusted to any runway system and or airport location. The prediction horizon is larger than 45 min (as required by air traffic control) and updated every 10 minutes. It predicts the concepts of operations and procedures established by DFS and it further predicts additional temporal separations for in-trail traffic. A specific feature of the WSVBS is the usage of both measured and predicted meteorological quantities as input to wake vortex prediction. In ground proximity where the probability to encounter wake vortices is highest, the wake predictor employs measured environmental parameters that yield superior prediction results. For the less critical part aloft, which can not be monitored completely by instrumentation, the meteorological parameters are taken from dedicated numerical terminal weather predictions. The wake vortex model predicts envelopes for vortex position and strength which implicitly consider the quality of the meteorological input data. This feature is achieved by a training procedure which employs statistics of measured and predicted meteorological parameters and the resulting wake vortex behaviour. The WSVBS combines various conservative elements that presumably lead to a very high overall safety level of the WSVBS. The combination of these conservative measures certainly leads to a very high but currently unknown overall safety. Once the methodology of a comprehensive risk analysis will be established, it is planned to adjust all components to appropriate and consistent confidence levels. The WSVBS has demonstrated its functionality at Frankfurt airport during 66 days in the period from 18/12/06 until 28/02/07. The performance test indicates that (i) the system ran stable - no forecast breakdowns occurred, (ii) aircraft separations could have been reduced in 75% of the time compared to ICAO standards, (iii) reduced separation procedures could have been continuously applied for at least several tens of minutes and up to several hours occasionally, (iv) the predictions were correct as for about 1100 landings observed during 16 days no warnings occurred from the LIDAR. Fast-time simulations reveal that adapted concepts of operation yield significant reductions in delay and/or an increase in capacity to 3% taking into account the real traffic mix and operational constraints in the period of one month. Before the WSVBS can be handed over for final adaptations to become a customized fully operational system some further steps are planned. A risk analysis needs to be pursued to convince all stakeholders of the usefulness and capabilities of the system.

Rheological behavior on treated Malaysian crude oil

NASA Astrophysics Data System (ADS)

Chandran, Krittika; Sinnathambi, Chandra Mohan

2016-11-01

Crude oil is always produced with water. This association causes many problems during oil production, arising from the formation of emulsion. Emulsion is an undesirable substance that increases operational and capital cost in the pipeline and processing equipment. To overcome this issue, demulsifiers are formulated to break the emulsion, where they are able to separate the water-oil emulsions to their respective phases. The emulsifier's main function is to reduce the interfacial tension properties of the emulsion. For this research, both the EOR and natural water-in-oil emulsions were treated with low a concentration demulsifier. The main objective of this paper is to determine the dynamic viscosity and rheological properties of the treated EOR and natural emulsion. The dynamic viscosity was obtained using the Brook-field Digital Viscometer. The components that influence the emulsion's rheological properties are the temperature, shear rate and shear stress. The results obtained demonstrate that the viscosity of the treated crude decreases and portrays the Non-Newtonian shear thinning "pseudo-plastic" behavior. Besides that, to determine the interfacial film of the treated crude, the spinning drop tensiometer was used. With the addition of demulsifier, the thinning rate of the oil film accelerates whereby there is a linear decrease in the interfacial tension with an increase in time. Therefore, from the results, it can be observed that the rheology study plays a significant role in the demulsification test. Furthermore, both the rheology approaches showed that time, temperature, shear rate and shear stress have a great impact on the viscosity behavior as well as the IFT.

Interfacial rheology of model particles at liquid interfaces and its relation to (bicontinuous) Pickering emulsions

NASA Astrophysics Data System (ADS)

Thijssen, J. H. J.; Vermant, J.

2018-01-01

Interface-dominated materials are commonly encountered in both science and technology, and typical examples include foams and emulsions. Conventionally stabilised by surfactants, emulsions can also be stabilised by micron-sized particles. These so-called Pickering-Ramsden (PR) emulsions have received substantial interest, as they are model arrested systems, rather ubiquitous in industry and promising templates for advanced materials. The mechanical properties of the particle-laden liquid-liquid interface, probed via interfacial rheology, have been shown to play an important role in the formation and stability of PR emulsions. However, the morphological processes which control the formation of emulsions and foams in mixing devices, such as deformation, break-up, and coalescence, are complex and diverse, making it difficult to identify the precise role of the interfacial rheological properties. Interestingly, the role of interfacial rheology in the stability of bicontinuous PR emulsions (bijels) has been virtually unexplored, even though the phase separation process which leads to the formation of these systems is relatively simple and the interfacial deformation processes can be better conceptualised. Hence, the aims of this topical review are twofold. First, we review the existing literature on the interfacial rheology of particle-laden liquid interfaces in rheometrical flows, focussing mainly on model latex suspensions consisting of polystyrene particles carrying sulfate groups, which have been most extensively studied to date. The goal of this part of the review is to identify the generic features of the rheology of such systems. Secondly, we will discuss the relevance of these results to the formation and stability of PR emulsions and bijels.

Control of vortical separation on conical bodies

NASA Technical Reports Server (NTRS)

Mourtos, Nikos J.; Roberts, Leonard

1987-01-01

In a variety of aeronautical applications, the flow around conical bodies at incidence is of interest. Such applications include, but are not limited to, highly maneuverable aircraft with delta wings, the aerospace plane and nose portions of spike inlets. The theoretical model used has three parts. First, the single line vortex model is used within the framework of slender body theory, to compute the outer inviscid field for specified separation lines. Next, the three dimensional boundary layer is represented by a momentum equation for the cross flow, analogous to that for a plane boundary layer; a von Karman Pohlhausen approximation is applied to solve this equation. The cross flow separation for both laminar and turbulent layers is determined by matching the pressure at the upper and lower separation points. This iterative procedure yields a unique solution for the separation lines and consequently for the position of the vortices and the vortex lift on the body. Lastly, control of separation is achieved by blowing tangentially from a slot located along a cone generator. It is found that for very small blowing coefficients, the separation can be postponed or suppressedy completely.

Simulation of self-induced unsteady motion in the near wake of a Joukowski airfoil

NASA Technical Reports Server (NTRS)

Ghia, K. N.; Osswald, G. A.; Ghia, U.

1986-01-01

The unsteady Navier-Stokes analysis is shown to be capable of analyzing the massively separated, persistently unsteady flow in the post-stall regime of a Joukowski airfoil for an angle of attack as high as 53 degrees. The analysis has provided the detailed flow structure, showing the complex vortex interaction for this configuration. The aerodynamic coefficients for lift, drag, and moment were calculated. So far only the spatial structure of the vortex interaction was computed. It is now important to potentially use the large-scale vortex interactions, an additional energy source, to improve the aerodynamic performance.

Visualization of Dynamic Vortex Structures in Magnetic Films with Uniaxial Anisotropy (Micromagnetic Simulation)

NASA Astrophysics Data System (ADS)

Zverev, V. V.; Izmozherov, I. M.; Filippov, B. N.

2018-02-01

Three-dimensional computer simulation of dynamic processes in a moving domain boundary separating domains in a soft magnetic uniaxial film with planar anisotropy is performed by numerical solution of Landau-Lifshitz-Gilbert equations. The developed visualization methods are used to establish the connection between the motion of surface vortices and antivortices, singular (Bloch) points, and core lines of intrafilm vortex structures. A relation between the character of magnetization dynamics and the film thickness is found. The analytical models of spatial vortex structures for imitation of topological properties of the structures observed in micromagnetic simulation are constructed.

TREATMENT AND SOLIDS MANAGEMENT

EPA Science Inventory

A variety of high-rate treatment methods show a potential to handle WWF including: physical separation with and without chemical addition (e.g., enhanced settling, fine-mesh screening, vortex separation, dual-media high-rate filtration, dissolved air flotation, activated carbon, ...

In-flight flow visualization characteristics of the NASA F-18 high alpha research vehicle at high angles of attack

NASA Technical Reports Server (NTRS)

Fisher, David F.; Delfrate, John H.; Richwine, David M.

1991-01-01

Surface and off-surface flow visualization techniques were used to visualize the 3-D separated flows on the NASA F-18 high alpha research vehicle at high angles of attack. Results near the alpha = 25 to 26 deg and alpha = 45 to 49 deg are presented. Both the forebody and leading edge extension (LEX) vortex cores and breakdown locations were visualized using smoke. Forebody and LEX vortex separation lines on the surface were defined using an emitted fluid technique. A laminar separation bubble was also detected on the nose cone using the emitted fluid technique and was similar to that observed in the wind tunnel test, but not as extensive. Regions of attached, separated, and vortical flow were noted on the wing and the leading edge flap using tufts and flow cones, and compared well with limited wind tunnel results.

The use of hydrodynamic vortex separators and screening systems to improve water quality.

PubMed

Andoh, R Y G; Saul, A J

2003-01-01

The paper reviews the evolution of Hydrodynamic Vortex Separators (HDVS) in the context of application as high rate rotary flow separators for achieving water quality improvements to meet with regulatory requirements in Europe and North America. The types of HDVS and their application for the control of wet-weather discharges such as combined sewer overflows (CSOs), sanitary sewer overflows (SSOs) and stormwater are outlined and a number of myths surrounding their use, dispelled. Reference is made to outputs of peer reviewed comprehensive monitoring, evaluation and demonstration projects on pilot and full-scale installations to demonstrate the efficacy and extensive track record of these systems. Recent developments and innovations in HDVS technologies are discussed, focusing on their combined use as solids liquid separators, contact vessels for wastewater disinfection, the incorporation of self-cleansing screening devices for the control of aesthetic pollutants (e.g. floatables) and the use of computational modelling for optimisation.

Imaging gastric structuring of lipid emulsions and its effect on gastrointestinal function: a randomized trial in healthy subjects.

PubMed

Steingoetter, Andreas; Radovic, Tijana; Buetikofer, Simon; Curcic, Jelena; Menne, Dieter; Fried, Michael; Schwizer, Werner; Wooster, Tim J

2015-04-01

Efficient fat digestion requires fat processing within the stomach and fat sensing in the intestine. Both processes also control gastric emptying and gastrointestinal secretions. We aimed to visualize the influence of the intragastric stability of fat emulsions on their dynamics of gastric processing and structuring and to assess the effect this has on gastrointestinal motor and secretory functions. Eighteen healthy subjects with normal body mass index (BMI) were studied on 4 separate occasions in a double-blind, randomized, crossover design. Magnetic resonance imaging (MRI) data of the gastrointestinal tract and blood triglycerides were recorded before and for 240 min after the consumption of the following 4 different fat emulsions: lipid emulsion 1 (LE1; acid stable, 0.33 μm), lipid emulsion 2 (LE2; acid stable, 52 μm), lipid emulsion 3 (LE3; acid unstable, solid fat, 0.32 μm), and lipid emulsion 4 (LE4; acid unstable, liquid fat, 0.38 μm). Intragastric emulsion instability was associated with a change in gastric emptying. Acid-unstable emulsions exhibited biphasic and faster emptying profiles than did the 2 acid-stable emulsions (P ≤ 0.0001). When combined with solid fat (LE3), different dynamics of postprandial gallbladder volume were induced (P ≤ 0.001). For acid-stable emulsions, a reduction of droplet size by 2 orders of magnitude [LE1 (0.33 μm) compared with LE2 (52 μm)] delayed gastric emptying by 38 min. Although acid-stable (LE1 and LE2) and redispersible (LE4) emulsions caused a constant increase in blood triglycerides, no increase was detectable for LE3 (P < 0.0001). For LE3, MRI confirmed the generation of large fat particles during gastric processing, which emptied into and progressed through the small intestine. MRI allows the detailed characterization of the in vivo fate of lipid emulsions. The acute effects of lipid emulsions on gastric emptying, gallbladder volume, and triglyceride absorption are dependent on microstructural changes undergone during consumption. Gastric peristalsis and secretion were effective at redispersing pools of liquid fat in the stomach. This trial was registered at clinicaltrials.gov as NCT01253005. © 2015 American Society for Nutrition.

Updated Results for the Wake Vortex Inverse Model

NASA Technical Reports Server (NTRS)

Robins, Robert E.; Lai, David Y.; Delisi, Donald P.; Mellman, George R.

2008-01-01

NorthWest Research Associates (NWRA) has developed an Inverse Model for inverting aircraft wake vortex data. The objective of the inverse modeling is to obtain estimates of the vortex circulation decay and crosswind vertical profiles, using time history measurements of the lateral and vertical position of aircraft vortices. The Inverse Model performs iterative forward model runs using estimates of vortex parameters, vertical crosswind profiles, and vortex circulation as a function of wake age. Iterations are performed until a user-defined criterion is satisfied. Outputs from an Inverse Model run are the best estimates of the time history of the vortex circulation derived from the observed data, the vertical crosswind profile, and several vortex parameters. The forward model, named SHRAPA, used in this inverse modeling is a modified version of the Shear-APA model, and it is described in Section 2 of this document. Details of the Inverse Model are presented in Section 3. The Inverse Model was applied to lidar-observed vortex data at three airports: FAA acquired data from San Francisco International Airport (SFO) and Denver International Airport (DEN), and NASA acquired data from Memphis International Airport (MEM). The results are compared with observed data. This Inverse Model validation is documented in Section 4. A summary is given in Section 5. A user's guide for the inverse wake vortex model is presented in a separate NorthWest Research Associates technical report (Lai and Delisi, 2007a).

Influence of palmitoyl pentapeptide and Ceramide III B on the droplet size of nanoemulsion

NASA Astrophysics Data System (ADS)

Sondari, Dewi; Haryono, Agus; Harmami, Sri Budi; Randy, Ahmad

2010-05-01

The influence of the Palmitoyl Pentapeptide (PPp) and Ceramide IIIB (Cm III B) as active ingredients on the droplet size of nano-emulsion was studied using different kinds of oil (avocado oil, sweet almond oil, jojoba oil, mineral oil and squalene). The formation of nano-emulsions were prepared in water mixed non ionic surfactant/oils system using the spontaneous emulsification mechanism. The aqueous solution, which consist of water and Tween® 20 as a hydrophilic surfactant was mixed homogenously. The organic solution, which consist of oil and Span® 80 as a lipophilic surfactant was mixed homogenously in ethanol. Ethanol was used as a water miscible solvent, which can help the formation of nano-emulsion. The oil phase (containing the blend of surfactant Span® 80, ethanol, oil and active ingredient) and the aqueous phase (containing water and Tween® 20) were separately prepared at room temperatures. The oil phase was slowly added into aqueous phase under continuous mechanical agitation (18000 rpm). All samples were subsequently homogenized with Ultra-Turrax for 30 minutes. The characterizations of nano-emulsion were carried out using photo-microscope and particle size analyzer. Addition of active ingredients on the formation of nano-emulsion gave smallest droplet size compared without active ingredients addition on the formation of nano-emulsion. Squalene oil with Palmitoyl Pentapeptide (PPm) and Ceramide IIIB (Cm IIIB) gave smallest droplet size (184.0 nm) compared without Palmitoyl Pentapeptide and Ceramide IIIB (214.9 nm), however the droplets size of the emulsion prepared by the other oils still in the range of nano-emulsion (below 500 nm). The stability of nano-emulsion was observed using two methods. In one method, the stability of nano-emulsion was observed for three months at temperature of 5°C and 50°C, while in the other method, the stability nano-emulsion was observed by centrifuged at 12000 rpm for 30 minutes. Nanoemulsion with active ingredient was remained stable even when stored until three months. Coalescence process between the droplets was not occurred significantly and droplet size was still below 500 nm. Over all, the emulsion remained stable, even it was centrifuged at 12000 rpm for 30 minutes.

OPERA experiment and its releted emulsion techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ariga, Akitaka

2008-02-21

The OPERA experiment is designed to clarify neutrino oscillation by detecting appearance of {nu}{sub {tau}} in pure {nu}{sub {mu}} beam through a long baseline method (CNGS beam from cern to the Gran Sasso laboratory). The key technique is the use of emulsion films and their scanning. We developed a new high speed scanning system with speed of 50 cm{sup 2}/h and it was successfully demonstrated in 2006 CNGS commissioning. The new scanning system is not only meant for the OPERA experiment, but it has large potential of applications. For example, measurement of {nu}{sub e} with strong separation power against {pi}{supmore » 0}. Or a compact emulsion spectrometer for future neutrino experiments.« less

Spectrum study on unsteadiness of shock wave-vortex ring interaction

NASA Astrophysics Data System (ADS)

Dong, Xiangrui; Yan, Yonghua; Yang, Yong; Dong, Gang; Liu, Chaoqun

2018-05-01

Shock oscillation with low-frequency unsteadiness commonly occurs in supersonic flows and is a top priority for the control of flow separation caused by shock wave and boundary layer interaction. In this paper, the interaction of the shock caused by the compression ramp and the vortex rings generated by a micro-vortex generator (MVG) in a supersonic flow at Ma = 2.5 is simulated by the implicit large eddy simulation method. The analysis of observation and the frequency of both the vortex ring motion and the shock oscillation is carried out. The results show that the shock produced by a compression ramp flow at Ma = 2.5 has a dominant non-dimensional low frequency, which is around St = 0.002, while the vortex rings behind the MVG have a dominant high frequency which is around St = 0.038. The dominant low frequency of the shock, which is harmful, can be removed or weakened through the shock-vortex ring interaction by the vortex rings which generate high frequency fluctuations. In the shock and vortex ring interaction region, a dominant high frequency St = 0.037-0.038 has been detected rather than the low frequency St = 0.002, which indicates that the vortex ring is stiff enough to break or weaken the shock. This analysis could provide an effective tool to remove or weaken the low frequency pressure fluctuation below 500 Hz, which has a negative effect on the flight vehicle structures and the environmental protection, through the high frequency vortex generation.

On the formation of vortex rings in coaxial tubes

NASA Astrophysics Data System (ADS)

Gan, Lian

2011-11-01

The formation of vortex rings within coaxial tubes of different diameter is investigated experimentally and numerically. PIV measurements were carried out in a water tank equipped with a piston-cylinder apparatus used to generate vortex rings inside a series of coaxial tubes with tube to piston diameter ratios, DT / D , ranging from 4 to 1.5. In order to distinguish between the effect confinement has on the formation of isolated vortex rings from those formed with a trailing jet flow, non- dimensional stroke ratios below and above the formation number were investigated, L / D = 2 . 5 and 10 respectively. For DT / D > 2 and L / D s below the formation number the kinematics of the vortex rings follow classical inviscid theory in so much as their self-induced velocity decreases linearly with decreasing tube diameter in accordance with the image theorem. For DT / D <= 2 boundary layer separation along the tube wall begins to interfere with the vortex during its roll-up phase. For vortex rings below the formation number, the vortex core is briefly arrested upon completion of the piston stroke. On the other hand, long L / D s give rise to even more complex dynamics. When DT / D = 2 the interaction between boundary layer and the starting jet acts to suppress vortex ring formation altogether. However, as confinement is increased further to DT / D = 1 . 5 the formation of a lead vortex ring re-appears but with a circulation lower than the formation number before rapidly decaying.

Flow visualizations of perpendicular blade vortex interactions

NASA Technical Reports Server (NTRS)

Rife, Michael C.; Davenport, William J.

1992-01-01

Helium bubble flow visualizations have been performed to study perpendicular interaction of a turbulent trailing vortex and a rectangular wing in the Virginia Tech Stability Tunnel. Many combinations of vortex strength, vortex-blade separation (Z(sub s)) and blade angle of attack were studied. Photographs of representative cases are presented. A range of phenomena were observed. For Z(sub s) greater than a few percent chord the vortex is deflected as it passes the blade under the influence of the local streamline curvature and its image in the blade. Initially the interaction appears to have no influence on the core. Downstream, however, the vortex core begins to diffuse and grow, presumably as a consequence of its interaction with the blade wake. The magnitude of these effects increases with reduction in Z(sub s). For Z(sub s) near zero the form of the interaction changes and becomes dependent on the vortex strength. For lower strengths the vortex appears to split into two filaments on the leading edge of the blade, one passing on the pressure and one passing on the suction side. At higher strengths the vortex bursts in the vicinity of the leading edge. In either case the core of its remnants then rapidly diffuse with distance downstream. Increase in Reynolds number did not qualitatively affect the flow apart from decreasing the amplitude of the small low-frequency wandering motions of the vortex. Changes in wing tip geometry and boundary layer trip had very little effect.

The effects of micro-vortex generators on normal shock wave/boundary layer interactions

NASA Astrophysics Data System (ADS)

Herges, Thomas G.

Shock wave/boundary-layer interactions (SWBLIs) are complex flow phenomena that are important in the design and performance of internal supersonic and transonic flow fields such as engine inlets. This investigation was undertaken to study the effects of passive flow control devices on normal shock wave/boundary layer interactions in an effort to gain insight into the physics that govern these complex interactions. The work concentrates on analyzing the effects of vortex generators (VGs) as a flow control method by contributing a greater understanding of the flowfield generated by these devices and characterizing their effects on the SWBLI. The vortex generators are utilized with the goal of improving boundary layer health (i.e., reducing/increasing the boundary-layer incompressible shape factor/skin friction coefficient) through a SWBLI, increasing pressure recovery, and reducing flow distortion at the aerodynamic interface plane while adding minimal drag to the system. The investigation encompasses experiments in both small-scale and large-scale inlet testing, allowing multiple test beds for improving the characterization and understanding of vortex generators. Small-scale facility experiments implemented instantaneous schlieren photography, surface oil-flow visualization, pressure-sensitive paint, and particle image velocimetry to characterize the effects of an array of microramps on a normal shock wave/boundary-layer interaction. These diagnostics measured the time-averaged and instantaneous flow organization in the vicinity of the microramps and SWBLI. The results reveal that a microramp produces a complex vortex structure in its wake with two primary counter-rotating vortices surrounded by a train of Kelvin- Helmholtz (K-H) vortices. A streamwise velocity deficit is observed in the region of the primary vortices in addition to an induced upwash/downwash which persists through the normal shock with reduced strength. The microramp flow control also increased the spanwise-averaged skin-friction coefficient and reduced the spanwise-averaged incompressible shape factor, thereby improving the health of the boundary layer. The velocity in the near-wall region appears to be the best indicator of microramp effectiveness at controlling SWBLIs. Continued analysis of additional micro-vortex generator designs in the small-scale facility revealed reduced separation within a subsonic diffuser downstream of the normal shock wave/boundary layer interaction. The resulting attached flow within the diffuser from the micro-vortex generator control devices reduces shock wave position and pressure RMS fluctuations within the diffuser along with increased pressure recovery through the shock and at the entrance of the diffuser. The largest effect was observed by the micro-vortex generators that produce the strongest streamwise vortices. High-speed pressure measurements also indicated that the vortex generators shift the energy of the pressure fluctuations to higher frequencies. Implementation of micro-vortex generators into a large-scale, supersonic, axisymmetric, relaxed-compression inlet have been investigated with the use of a unique and novel flow-visualization measurement system designed and successfully used for the analysis of both upstream micro-VGs (MVGs) and downstream VGs utilizing surface oil-flow visualization and pressure-sensitive paint measurements. The inlet centerbody and downstream diffuser vortex-generator regions were imaged during wind-tunnel testing internally through the inlet cowl with the diagnostic system attached to the cowl. Surface-flow visualization revealed separated regions along the inlet centerbody for large mass-flow rates without vortex generators. Upstream vortex generators did reduce separation in the subsonic diffuser, and a unique perspective of the flowfield produced by the downstream vortex generators was obtained. In addition, pressure distributions on the inlet centerbody and vortex generators were measured with pressure-sensitive paint. At low mass-flow ratios the onset of buzz occurs in the large-scale low-boom inlet. Inlet buzz and how it is affected by vortex generators was characterized using shock tracking through high-speed schlieren imaging and pressure fluctuation measurements. The analysis revealed a dominant low frequency oscillation at 21.0 Hz for the single-stream inlet, corresponding with the duration of one buzz cycle. Pressure oscillations prior to the onset of buzz were not detected, leaving the location where the shock wave triggers large separation on the compression spike as the best indicator for the onset of buzz. The driving mechanism for a buzz cycle has been confirmed as the rate of depressurization and repressurization of the inlet as the buzz cycle fluctuates between an effectively unstarted (blocked) inlet and supercritical operation (choked flow), respectively. High-frequency shock position oscillations/pulsations (spike buzz) were also observed throughout portions of the inlet buzz cycle. The primary effect of the VGs was to trigger buzz at a higher mass-flow ratio.

Generating broadband vortex modes in ring-core fiber by using a plasmonic q-plate.

PubMed

Ye, Jingfu; Li, Yan; Han, Yanhua; Deng, Duo; Su, Xiaoya; Song, He; Gao, Jianmin; Qu, Shiliang

2017-08-15

A mode convertor was proposed and investigated for generating vortex modes in a ring-core fiber based on a plasmonic q-plate (PQP), which is composed of specially organized L-shaped resonator (LSR) arrays. A multicore fiber was used to transmit fundamental modes, and the LSR arrays were used to modulate phases of these fundamental modes. Behind the PQP, the transmitted fundamental modes with gradient phase distribution can be considered as the incident lights for generating broadband vortex modes in the ring-core fiber filter. The topological charges of generated vortex modes can be various by using an optical PQP with different q, and the chirality of the generated vortex mode can be controlled by the sign of q and handedness of the incident circularly polarized light. The operation bandwidth is 800 nm in the range of 1200-2000 nm, which covers six communication bands from the O band to the U band. The separation of vortex modes also was addressed by using a dual ring-core fiber. The mode convertor is of potential interest for connecting a traditional network and vortex communication network.

On the aeroacoustic tonal noise generation mechanism of a sharp-edged plate.

PubMed

Moreau, Danielle J; Brooks, Laura A; Doolan, Con J

2011-04-01

This letter presents an experimental study on the tonal noise generated by a sharp-edged flat plate at low-to-moderate Reynolds number. Flow and far-field noise data reveal that, in this particular case, the tonal noise appears to be governed by vortex shedding processes. Also related to the existence of the tonal noise is a region of separated flow slightly upstream of the trailing edge. Hydrodynamic fluctuations at selected vortex shedding frequencies are strongly amplified by the inflectional mean velocity profile in the separated shear layer. The amplified hydrodynamic fluctuations are diffracted by the trailing edge, producing strong tonal noise.

A Structured Grid Based Solution-Adaptive Technique for Complex Separated Flows

NASA Technical Reports Server (NTRS)

Thornburg, Hugh; Soni, Bharat K.; Kishore, Boyalakuntla; Yu, Robert

1996-01-01

The objective of this work was to enhance the predictive capability of widely used computational fluid dynamic (CFD) codes through the use of solution adaptive gridding. Most problems of engineering interest involve multi-block grids and widely disparate length scales. Hence, it is desirable that the adaptive grid feature detection algorithm be developed to recognize flow structures of different type as well as differing intensity, and adequately address scaling and normalization across blocks. In order to study the accuracy and efficiency improvements due to the grid adaptation, it is necessary to quantify grid size and distribution requirements as well as computational times of non-adapted solutions. Flow fields about launch vehicles of practical interest often involve supersonic freestream conditions at angle of attack exhibiting large scale separate vortical flow, vortex-vortex and vortex-surface interactions, separated shear layers and multiple shocks of different intensity. In this work, a weight function and an associated mesh redistribution procedure is presented which detects and resolves these features without user intervention. Particular emphasis has been placed upon accurate resolution of expansion regions and boundary layers. Flow past a wedge at Mach=2.0 is used to illustrate the enhanced detection capabilities of this newly developed weight function.

Numerical simulation of separated flows. Ph.D. Thesis - Stanford Univ., Calif.

NASA Technical Reports Server (NTRS)

Spalart, P. R.; Leonard, A.; Baganoff, D.

1983-01-01

A new numerical method, based on the Vortex Method, for the simulation of two-dimensional separated flows, was developed and tested on a wide range of gases. The fluid is incompressible and the Reynolds number is high. A rigorous analytical basis for the representation of the Navier-Stokes equation in terms of the vorticity is used. An equation for the control of circulation around each body is included. An inviscid outer flow (computed by the Vortex Method) was coupled with a viscous boundary layer flow (computed by an Eulerian method). This version of the Vortex Method treats bodies of arbitrary shape, and accurately computes the pressure and shear stress at the solid boundary. These two quantities reflect the structure of the boundary layer. Several versions of the method are presented and applied to various problems, most of which have massive separation. Comparison of its results with other results, generally experimental, demonstrates the reliability and the general accuracy of the new method, with little dependence on empirical parameters. Many of the complex features of the flow past a circular cylinder, over a wide range of Reynolds numbers, are correctly reproduced.

Investigation of compressible vortex flow characteristics

NASA Technical Reports Server (NTRS)

Muirhead, V. U.

1977-01-01

The nature of intense air vortices was studied and the factors which determine the intensity and rate of decay of both single and pairs of vortices were investigated. Vortex parameters of axial pressure differential, circulation, outflow rates, separation distance and directions of rotation were varied. Unconfined vortices, generated by a single rotating cage, were intensified by an increasing axial pressure gradient. Breakdown occurred when the axial gradient became negligible. The core radius was a function of the axial gradient. Dual vortices, generated by two counterrotating cages, rotated opposite to the attached cages. With minimum spacing only one vortex was formed which rotated in a direction opposite to the attached cage. When one cage rotated at half the speed of the other cage, one vortex formed at the higher speed cage rotating in the cage direction.

Subsonic aerodynamic characteristics of interacting lifting surfaces with separated flow around sharp edges predicted by a vortex-lattice method

NASA Technical Reports Server (NTRS)

Lamar, J. E.; Gloss, B. B.

1975-01-01

Because the potential flow suction along the leading and side edges of a planform can be used to determine both leading- and side-edge vortex lift, the present investigation was undertaken to apply the vortex-lattice method to computing side-edge suction force for isolated or interacting planforms. Although there is a small effect of bound vortex sweep on the computation of the side-edge suction force, the results obtained for a number of different isolated planforms produced acceptable agreement with results obtained from a method employing continuous induced-velocity distributions. By using the method outlined, better agreement between theory and experiment was noted for a wing in the presence of a canard than was previously obtained.

The interaction between a propagating coastal vortex and topographic waves

NASA Astrophysics Data System (ADS)

Parry, Simon Wyn

This thesis investigates the motion of a point vortex near coastal topography in a rotating frame of reference at constant latitude (f-plane) in the linear and weakly nonlinear limits. Topography is considered in the form of an infinitely long escarpment running parallel to a wall. The vortex motion and topographic waves are governed by the conservation of quasi-geostrophic potential vorticity in shallow water, from which a nonlinear system of equations is derived. First the linear limit is studied for three cases; a weak vortex on- and off-shelf and a weak vortex close to the wall. For the first two cases it is shown that to leading order the vortex motion is stationary and a solution for the topographic waves at the escarpment can be found in terms of Fourier integrals. For a weak vortex close to a wall, the leading order solution is a steadily propagating vortex with a topographic wavetrain at the step. Numerical results for the higher order interactions are also presented and explained in terms of conservation of momentum in the along-shore direction. For the second case a resonant interaction between the vortex and the waves occurs when the vortex speed is equal to the maximum group velocity of the waves and the linear response becomes unbounded at large times. Thus it becomes necessary to examine the weakly nonlinear near-resonant case. Using a long wave approximation a nonlinear evolution equation for the interface separating the two regions of differing relative potential vorticity is derived and has similar form to the BDA (Benjamin, Davies, Acrivos 1967) equation. Results for the leading order steadily propagating vortex and for the vortex-wave feedback problem are calculated numerically using spectral multi-step Adams methods.

Orbiter/carrier separation for the ALT free flight no. 1 reference trajectories. Mission planning, mission analysis and software formulation

NASA Technical Reports Server (NTRS)

Glenn, G. M.

1976-01-01

Details of the generation of the separation trajectories are discussed. The analysis culminated in definition of separation trajectories between physical separation and orbiter/carrier vortex clearance. Specifications, assumptions and analytical approach used to generate the separation trajectories are presented. Results of the analytical approach are evaluated. Conclusions and recommendations are summarized. Supporting references are listed.

Study of the vortex conditions of wings with large sweepback by extrapolation of the Jones method

NASA Technical Reports Server (NTRS)

Hirsch, P.

1980-01-01

The pockets of separation originating on the leading edges are surrounded by vortex sheets. Their configuration and intensity were determined by four conditions with the JONES approximation, which is itself corrected by a simple logic. Field pressures and stresses were computed for different cases and are compared with test results (pure deltas, swallow tails, truncations, strakes, ducks, fuselage).

Surface-Streamline Flow Visualization

NASA Technical Reports Server (NTRS)

Langston, L.; Boyle, M.

1985-01-01

Matrix of ink dots covers matte surface of polyester drafting film. Film placed against wind-tunnel wall. Layer of methyl salicylate (oil of wintergreen) sprayed over dotted area. Ink dot streaklines show several characteristics of flow, including primary saddle point of separations, primary horseshoe vortex and smaller vortex at cylinder/ endwall junction. Surface streamline flow visualization technique suitable for use in low-speed windtunnels or other low-speed gas flows.

Scattering and propagation of a Laguerre-Gaussian vortex beam by uniaxial anisotropic bispheres

NASA Astrophysics Data System (ADS)

Qu, Tan; Wu, Zhensen; Shang, Qingchao; Li, Zhengjun; Wu, Jiaji; Li, Haiying

2018-04-01

Within the framework of the generalized multi-particle Mie (GMM) theory, analytical solution to electromagnetic scattering of two interacting homogeneous uniaxial anisotropic spheres by a Laguerre-Gaussian (LG) vortex beam is investigated. The particles with different size and dielectric parameter tensor elements are arbitrarily configured. Based on the continuous boundary conditions at each sphere surface, the interactive scattering coefficients are derived. The internal and near-surface field is investigated to describe the propagation of LG vortex beam through the NaCl crystal. In addition, the far fields of some typical anisotropic medium such as LiNbO3, TiO2 bispheres illuminated by an LG vortex beam are numerically presented in detail to analyze the influence of the anisotropic parameters, sphere positions, separation distance and topological charge etc. The results show that LG vortex beam has a better recovery after interacting with a spherical particle compared with Gaussian beam. The study in the paper are useful for the further research on the scattering and propagation characteristics of arbitrary vortex beam in anisotropic chains and periodic structure.

Vortex leading edge flap assembly for supersonic airplanes

NASA Technical Reports Server (NTRS)

Rudolph, Peter K. C. (Inventor)

1997-01-01

A leading edge flap (16) for supersonic transport airplanes is disclosed. In its stowed position, the leading edge flap forms the lower surface of the wing leading edge up to the horizontal center of the leading edge radius. For low speed operation, the vortex leading edge flap moves forward and rotates down. The upward curve of the flap leading edge triggers flow separation on the flap and rotational flow on the upper surface of the flap (vortex). The rounded shape of the upper fixed leading edge provides the conditions for a controlled reattachment of the flow on the upper wing surface and therefore a stable vortex. The vortex generates lift and a nose-up pitching moment. This improves maximum lift at low speed, reduces attitude for a given lift coefficient and improves lift to drag ratio. The mechanism (27) to move the vortex flap consists of two spanwise supports (24) with two diverging straight tracks (64 and 68) each and a screw drive mechanism (62) in the center of the flap panel (29). The flap motion is essentially normal to the airloads and therefore requires only low actuation forces.

Platelets Drive Thrombus Propagation in a Hematocrit and Glycoprotein VI-Dependent Manner in an In Vitro Venous Thrombosis Model.

PubMed

Lehmann, Marcus; Schoeman, Rogier M; Krohl, Patrick J; Wallbank, Alison M; Samaniuk, Joseph R; Jandrot-Perrus, Martine; Neeves, Keith B

2018-05-01

The objective of this study was to measure the role of platelets and red blood cells on thrombus propagation in an in vitro model of venous valvular stasis. A microfluidic model with dimensional similarity to human venous valves consists of a sinus distal to a sudden expansion, where for sufficiently high Reynolds numbers, 2 countercurrent vortices arise because of flow separation. The primary vortex is defined by the points of flow separation and reattachment. A secondary vortex forms in the deepest recess of the valve pocket characterized by low shear rates. An initial fibrin gel formed within the secondary vortex of a tissue factor-coated valve sinus. Platelets accumulated at the interface of the fibrin gel and the primary vortex. Red blood cells at physiological hematocrits were necessary to provide an adequate flux of platelets to support thrombus growth out of the valve sinus. A subpopulation of platelets that adhered to fibrin expose phosphatidylserine. Platelet-dependent thrombus growth was attenuated by inhibition of glycoprotein VI with a blocking Fab fragment or D-dimer. A 3-step process regulated by hemodynamics was necessary for robust thrombus propagation: First, immobilized tissue factor initiates coagulation and fibrin deposition within a low flow niche defined by a secondary vortex in the pocket of a model venous valve. Second, a primary vortex delivers platelets to the fibrin interface in a red blood cell-dependent manner. Third, platelets adhere to fibrin, activate through glycoprotein VI, express phosphatidylserine, and subsequently promote thrombus growth beyond the valve sinus and into the bulk flow. © 2018 American Heart Association, Inc.

Switchable Pickering Emulsions Stabilized by Awakened TiO2 Nanoparticle Emulsifiers Using UV/Dark Actuation.

PubMed

Zhang, Qing; Bai, Rui-Xue; Guo, Ting; Meng, Tao

2015-08-26

In this work, switchable Pickering emulsions that utilize UV/dark manipulation employ a type of smart TiO2 nanoparticle as emulsifiers. The emulsifiers can be awakened when needed via UV-induced degradation of grafted silanes on TiO2 nanoparticles. By tuning the surface wettability of TiO2 nanoparticles in situ via UV/dark actuation, emulsions stabilized by the nanoparticles can be reversibly switched between the water-in-oil (W/O) type and oil-in-water (O/W) type for several cycles. Due to the convertible wettability, the smart nanoparticle emulsifiers can be settled in either the oil phase or the water phase as desired during phase separation, making it convenient for recycling. The present work provides a facile and noninvasive method to freely manipulate the formation, breakage, and switching of the emulsion; this method has promising potential as a powerful technique for use in energy-efficient and environmentally friendly industries.

Turbulent flow separation control through passive techniques

NASA Technical Reports Server (NTRS)

Lin, J. C.; Howard, F. G.; Selby, G. V.

1989-01-01

Several passive separation control techniques for controlling moderate two-dimensional turbulent flow separation over a backward-facing ramp are studied. Small transverse and swept grooves, passive porous surfaces, large longitudinal grooves, and vortex generators were among the techniques used. It was found that, unlike the transverse and longitudinal grooves of an equivalent size, the 45-deg swept-groove configurations tested tended to enhance separation.

Cyclone separator having boundary layer turbulence control

DOEpatents

Krishna, Coimbatore R.; Milau, Julius S.

1985-01-01

A cyclone separator including boundary layer turbulence control that is operable to prevent undue build-up of particulate material at selected critical areas on the separator walls, by selectively varying the fluid pressure at those areas to maintain the momentum of the vortex, thereby preventing particulate material from inducing turbulence in the boundary layer of the vortical fluid flow through the separator.

Investigation of corner shock boundary layer interactions to understand inlet unstart

NASA Astrophysics Data System (ADS)

Funderburk, Morgan

2015-11-01

Inlet unstart is a detrimental phenomenon in dual-mode ramjet/scramjet engines that causes severe loss of thrust, large transient structural load, and potentially a loss of the aircraft. In order to analyze the effects that the corner shock boundary layer interaction (SBLI) has on initiating and perpetuating inlet unstart, a qualitative and quantitative investigation into mean and dynamic features of corner SBLI at various Mach numbers is made. Surface streakline visualization showed that the corner SBLI is highly three-dimensional with a dominant presence of corner separation vortex. Further, the peak r.m.s. pressure was located at the periphery of corner separation vortex, suggesting that the unsteady loading is caused by the corner vortex. Power spectral densities of wall-pressure fluctuations in the peak r.m.s. location were analyzed in order to characterize the dominant frequencies of oscillation of the flow structures and to unravel the dynamic interactions between them in order to expand the operating margin of future hypersonic air breathing vehicles.

Enhanced Airport Capacity Through Safe, Dynamic Reductions in Aircraft Separation: NASA's Aircraft VOrtex Spacing System (AVOSS)

NASA Technical Reports Server (NTRS)

OConnor, Cornelius J.; Rutishauser, David K.

2001-01-01

An aspect of airport terminal operations that holds potential for efficiency improvements is the separation criteria applied to aircraft for wake vortex avoidance. These criteria evolved to represent safe spacing under weather conditions conducive to the longest wake hazards, and are consequently overly conservative during a significant portion of operations. Under many ambient conditions, such as moderate crosswinds or turbulence, wake hazard durations are substantially reduced. To realize this reduction NASA has developed a proof-of-concept Aircraft Vortex Spacing System (AVOSS). Successfully operated in a real-time field demonstration during July 2000 at the Dallas Ft. Worth International Airport, AVOSS is a novel integration of weather sensors, wake sensors, and analytical wake prediction algorithms. Gains in airport throughput using AVOSS spacing as compared to the current criteria averaged 6%, with peak values approaching the theoretical maximum of 16%. The average throughput gain translates to 15-40% reductions in delay when applied to realistic capacity ratios at major airports.

Analytical observations on the aerodynamics of a delta wing with leading edge flaps

NASA Technical Reports Server (NTRS)

Oh, S.; Tavella, D.

1986-01-01

The effect of a leading edge flap on the aerodynamics of a low aspect ratio delta wing is studied analytically. The separated flow field about the wing is represented by a simple vortex model composed of a conical straight vortex sheet and a concentrated vortex. The analysis is carried out in the cross flow plane by mapping the wing trace, by means of the Schwarz-Christoffel transformation into the real axis of the transformed plane. Particular attention is given to the influence of the angle of attack and flap deflection angle on lift and drag forces. Both lift and drag decrease with flap deflection, while the lift-to-drag ratioe increases. A simple coordinate transformation is used to obtain a closed form expression for the lift-to-drag ratio as a function of flap deflection. The main effect of leading edge flap deflection is a partial suppression of the separated flow on the leeside of the wing. Qualitative comparison with experiments is presented, showing agreement in the general trends.

Performance and Selectivity of Ceramic Membranes in the Ultrafiltration of Model Emulsion in Saline

NASA Astrophysics Data System (ADS)

Ćwirko, Konrad; Kalbarczyk-Jedynak, Agnieszka

2017-06-01

Oily wastewaters from different onshore and offshore installations and from maritime transport pose a serious threat to the environment so they must be treated by multistage separation also including membrane processes. The main advantages of such membranes are high performance and selectivity, high resistance for temperature and pressure, resistance for acids, bases and solvents, long service life and for application - significant reduction of industries and transport environmental impact. This work presents the results of the process of separation of oil from the emulsion with NaCl addition. Research was performed with a use of laboratory installation with ceramic 300 kDa membrane. The analysis concerned performance and selectivity of a membrane in the function of time and test results have been subsequently compared with the requirements of the IMO.

Dynamically reconfigurable complex emulsions via tunable interfacial tensions

PubMed Central

Zarzar, Lauren D.; Sresht, Vishnu; Sletten, Ellen M.; Kalow, Julia A.; Blankschtein, Daniel; Swager, Timothy M.

2015-01-01

Emulsification is a powerful, well-known technique for mixing and dispersing immiscible components within a continuous liquid phase. Consequently, emulsions are central components of medicine, food and performance materials. Complex emulsions, including multiple emulsions and Janus droplets which contain hemispheres of differing material, are of increasing importance1 in pharmaceuticals and medical diagnostics2, in the fabrication of microparticles and capsules3–5 for food6, in chemical separations7, in cosmetics8, and in dynamic optics9. Because complex emulsion properties and functions are related to the droplet geometry and composition, the development of rapid, simple fabrication approaches allowing precise control over the droplets’ physical and chemical characteristics is critical. Significant advances in the fabrication of complex emulsions have been made using a number of procedures, ranging from large-scale, less precise techniques that give compositional heterogeneity using high-shear mixers and membranes10, to small-volume but more precise microfluidic methods11,12. However, such approaches have yet to create droplet morphologies that can be controllably altered after emulsification. Reconfigurable complex liquids potentially have greatly increased utility as dynamically tunable materials. Here we describe an approach to the one-step fabrication of three- and four-phase complex emulsions with highly controllable and reconfigurable morphologies. The fabrication makes use of the temperature-sensitive miscibility of hydrocarbon, silicone and fluorocarbon liquids, and is applied to both the microfluidic and the scalable batch production of complex droplets. We demonstrate that droplet geometries can be alternated between encapsulated and Janus configurations by varying the interfacial tensions using hydrocarbon and fluorinated surfactants including stimuli-responsive and cleavable surfactants. This yields a generalizable strategy for the fabrication of multiphase emulsions with controllably reconfigurable morphologies and the potential to create a wide range of responsive materials. PMID:25719669

Dynamically reconfigurable complex emulsions via tunable interfacial tensions.

PubMed

Zarzar, Lauren D; Sresht, Vishnu; Sletten, Ellen M; Kalow, Julia A; Blankschtein, Daniel; Swager, Timothy M

2015-02-26

Emulsification is a powerful, well-known technique for mixing and dispersing immiscible components within a continuous liquid phase. Consequently, emulsions are central components of medicine, food and performance materials. Complex emulsions, including Janus droplets (that is, droplets with faces of differing chemistries) and multiple emulsions, are of increasing importance in pharmaceuticals and medical diagnostics, in the fabrication of microparticles and capsules for food, in chemical separations, in cosmetics, and in dynamic optics. Because complex emulsion properties and functions are related to the droplet geometry and composition, the development of rapid, simple fabrication approaches allowing precise control over the droplets' physical and chemical characteristics is critical. Significant advances in the fabrication of complex emulsions have been made using a number of procedures, ranging from large-scale, less precise techniques that give compositional heterogeneity using high-shear mixers and membranes, to small-volume but more precise microfluidic methods. However, such approaches have yet to create droplet morphologies that can be controllably altered after emulsification. Reconfigurable complex liquids potentially have great utility as dynamically tunable materials. Here we describe an approach to the one-step fabrication of three- and four-phase complex emulsions with highly controllable and reconfigurable morphologies. The fabrication makes use of the temperature-sensitive miscibility of hydrocarbon, silicone and fluorocarbon liquids, and is applied to both the microfluidic and the scalable batch production of complex droplets. We demonstrate that droplet geometries can be alternated between encapsulated and Janus configurations by varying the interfacial tensions using hydrocarbon and fluorinated surfactants including stimuli-responsive and cleavable surfactants. This yields a generalizable strategy for the fabrication of multiphase emulsions with controllably reconfigurable morphologies and the potential to create a wide range of responsive materials.

Dynamically reconfigurable complex emulsions via tunable interfacial tensions

NASA Astrophysics Data System (ADS)

Zarzar, Lauren D.; Sresht, Vishnu; Sletten, Ellen M.; Kalow, Julia A.; Blankschtein, Daniel; Swager, Timothy M.

2015-02-01

Emulsification is a powerful, well-known technique for mixing and dispersing immiscible components within a continuous liquid phase. Consequently, emulsions are central components of medicine, food and performance materials. Complex emulsions, including Janus droplets (that is, droplets with faces of differing chemistries) and multiple emulsions, are of increasing importance in pharmaceuticals and medical diagnostics, in the fabrication of microparticles and capsules for food, in chemical separations, in cosmetics, and in dynamic optics. Because complex emulsion properties and functions are related to the droplet geometry and composition, the development of rapid, simple fabrication approaches allowing precise control over the droplets' physical and chemical characteristics is critical. Significant advances in the fabrication of complex emulsions have been made using a number of procedures, ranging from large-scale, less precise techniques that give compositional heterogeneity using high-shear mixers and membranes, to small-volume but more precise microfluidic methods. However, such approaches have yet to create droplet morphologies that can be controllably altered after emulsification. Reconfigurable complex liquids potentially have great utility as dynamically tunable materials. Here we describe an approach to the one-step fabrication of three- and four-phase complex emulsions with highly controllable and reconfigurable morphologies. The fabrication makes use of the temperature-sensitive miscibility of hydrocarbon, silicone and fluorocarbon liquids, and is applied to both the microfluidic and the scalable batch production of complex droplets. We demonstrate that droplet geometries can be alternated between encapsulated and Janus configurations by varying the interfacial tensions using hydrocarbon and fluorinated surfactants including stimuli-responsive and cleavable surfactants. This yields a generalizable strategy for the fabrication of multiphase emulsions with controllably reconfigurable morphologies and the potential to create a wide range of responsive materials.

To Model Chemical Reactivity in Heterogeneous Emulsions, Think Homogeneous Microemulsions.

PubMed

Bravo-Díaz, Carlos; Romsted, Laurence Stuart; Liu, Changyao; Losada-Barreiro, Sonia; Pastoriza-Gallego, Maria José; Gao, Xiang; Gu, Qing; Krishnan, Gunaseelan; Sánchez-Paz, Verónica; Zhang, Yongliang; Dar, Aijaz Ahmad

2015-08-25

Two important and unsolved problems in the food industry and also fundamental questions in colloid chemistry are how to measure molecular distributions, especially antioxidants (AOs), and how to model chemical reactivity, including AO efficiency in opaque emulsions. The key to understanding reactivity in organized surfactant media is that reaction mechanisms are consistent with a discrete structures-separate continuous regions duality. Aggregate structures in emulsions are determined by highly cooperative but weak organizing forces that allow reactants to diffuse at rates approaching their diffusion-controlled limit. Reactant distributions for slow thermal bimolecular reactions are in dynamic equilibrium, and their distributions are proportional to their relative solubilities in the oil, interfacial, and aqueous regions. Our chemical kinetic method is grounded in thermodynamics and combines a pseudophase model with methods for monitoring the reactions of AOs with a hydrophobic arenediazonium ion probe in opaque emulsions. We introduce (a) the logic and basic assumptions of the pseudophase model used to define the distributions of AOs among the oil, interfacial, and aqueous regions in microemulsions and emulsions and (b) the dye derivatization and linear sweep voltammetry methods for monitoring the rates of reaction in opaque emulsions. Our results show that this approach provides a unique, versatile, and robust method for obtaining quantitative estimates of AO partition coefficients or partition constants and distributions and interfacial rate constants in emulsions. The examples provided illustrate the effects of various emulsion properties on AO distributions such as oil hydrophobicity, emulsifier structure and HLB, temperature, droplet size, surfactant charge, and acidity on reactant distributions. Finally, we show that the chemical kinetic method provides a natural explanation for the cut-off effect, a maximum followed by a sharp reduction in AO efficiency with increasing alkyl chain length of a particular AO. We conclude with perspectives and prospects.

Effects of Emulsion Composition on Pulmonary Tobramycin Delivery During Antibacterial Perfluorocarbon Ventilation

PubMed Central

Orizondo, Ryan A.; Fabiilli, Mario L.; Morales, Marissa A.

2016-01-01

Abstract Background: The effectiveness of inhaled aerosolized antibiotics is limited by poor ventilation of infected airways. Pulmonary delivery of antibiotics emulsified within liquid perfluorocarbon [antibacterial perfluorocarbon ventilation (APV)] may solve this problem through better airway penetration and improved spatial uniformity. However, little work has been done to explore emulsion formulation and the corresponding effects on drug delivery during APV. This study investigated the effects of emulsion formulation on emulsion stability and the pharmacokinetics of antibiotic delivery via APV. Methods: Gravity-driven phase separation was examined in vitro by measuring emulsion tobramycin concentrations at varying heights within a column of emulsion over 4 hours for varying values of fluorosurfactant concentration (Cfs = 5–48 mg/mL H2O). Serum and pulmonary tobramycin concentrations in rats were then evaluated following pulmonary tobramycin delivery via aerosol or APV utilizing sufficiently stable emulsions of varying aqueous volume percentage (Vaq = 1%–5%), aqueous tobramycin concentration (Ct = 20–100 mg/mL), and Cfs (15 and 48 mg/mL H2O). Results: In vitro assessment showed sufficient spatial and temporal uniformity of tobramycin dispersion within emulsion for Cfs ≥15 mg/mL H2O, while lower Cfs values showed insufficient emulsification even immediately following preparation. APV with stable emulsion formulations resulted in 5–22 times greater pulmonary tobramycin concentrations at 4 hours post-delivery relative to aerosolized delivery. Concentrations increased with emulsion formulations utilizing increased Vaq (with decreased Ct) and, to a lesser extent, increased Cfs. Conclusions: The emulsion stability necessary for effective delivery is retained at Cfs values as low as 15 mg/mL H2O. Additionally, the pulmonary retention of antibiotic delivered via APV is significantly greater than that of aerosolized delivery and can be most effectively increased by increasing Vaq and decreasing Ct. APV has been further proven as an effective means of pulmonary drug delivery with the potential to significantly improve antibiotic therapy for lung disease patients. PMID:26741303

Effects of Microwave Radiation on Oil Recovery

NASA Astrophysics Data System (ADS)

Esmaeili, Abdollah

2011-12-01

A variety of oil recovery methods have been developed and applied to mature and depleted reservoirs in order to improve the efficiency. Microwave radiation oil recovery method is a relatively new method and has been of great interest in the recent years. Crude oil is typically co-mingled with suspended solids and water. To increase oil recovery, it is necessary to remove these components. The separation of oil from water and solids using gravitational settling methods is typically incomplete. Oil-in-water and oil-water-solid emulsions can be demulsified and separated into their individual layers by microwave radiation. The data also show that microwave separation is faster than gravity separation and can be faster than conventional heating at many conditions. After separation of emulsion into water and oil layers, water can be discharged and oil is collected. High-frequency microwave recycling process can recover oil and gases from oil shale, residual oil, drill cuttings, tar sands oil, contaminated dredge/sediments, tires and plastics with significantly greater yields and lower costs than are available utilizing existing known technologies. This process is environmentally friendly, fuel-generating recycler to reduce waste, cut emissions, and save energy. This paper presents a critical review of Microwave radiation method for oil recovery.

Asymmetric flow field flow fractionation for the characterization of globule size distribution in complex formulations: A cyclosporine ophthalmic emulsion case.

PubMed

Qu, Haiou; Wang, Jiang; Wu, Yong; Zheng, Jiwen; Krishnaiah, Yellela S R; Absar, Mohammad; Choi, Stephanie; Ashraf, Muhammad; Cruz, Celia N; Xu, Xiaoming

2018-03-01

Commonly used characterization techniques such as cryogenic-transmission electron microscopy (cryo-TEM) and batch-mode dynamic light scattering (DLS) are either time consuming or unable to offer high resolution to discern the poly-dispersity of complex drug products like cyclosporine ophthalmic emulsions. Here, a size-based separation and characterization method for globule size distribution using an asymmetric flow field flow fractionation (AF4) is reported for comparative assessment of cyclosporine ophthalmic emulsion drug products (model formulation) with a wide size span and poly-dispersity. Cyclosporine emulsion formulations that are qualitatively (Q1) and quantitatively (Q2) the same as Restasis® were prepared in house with varying manufacturing processes and analyzed using the optimized AF4 method. Based on our results, the commercially available cyclosporine ophthalmic emulsion has a globule size span from 30 nm to a few hundred nanometers with majority smaller than 100 nm. The results with in-house formulations demonstrated the sensitivity of AF4 in determining the differences in the globule size distribution caused by the changes to the manufacturing process. It is concluded that the optimized AF4 is a potential analytical technique for comprehensive understanding of the microstructure and assessment of complex emulsion drug products with high poly-dispersity. Published by Elsevier B.V.

Water-in-oil Pickering emulsions stabilized by stearoylated microcrystalline cellulose.

PubMed

Pang, Bo; Liu, Huan; Liu, Peiwen; Peng, Xinwen; Zhang, Kai

2018-03-01

Hydrophobic particles with static water contact angles larger than 90° are more like to stabilize W/O Pickering emulsions. In particular, high internal phase Pickering emulsions (HIPEs) are of great interest for diverse applications. However, W/O HIPEs have rarely been realized using sustainable biopolymers. Herein, we used stearoylated microcrystalline cellulose (SMCC) to stabilize W/O Pickering emulsions and especially, W/O HIPEs. Moreover, these W/O HIPEs can be further used as platforms for the preparation of porous materials, such as porous foams. Stearoylated microcrystalline cellulose (SMCC) was prepared by modifying MCC with stearoyl chloride under heterogeneous conditions. Using SMCC as emulsifiers, W/O medium and high internal phase Pickering emulsions (MIPEs and HIPEs) with various organic solvents as continuous phases were prepared using one-step and two-step methods, respectively. Polystyrene (PS) foams were prepared after polymerization of oil phase using HIPEs as templates and their oil/water separation capacity were studied. SMCC could efficiently stabilize W/O Pickering emulsions and HIPEs could only be prepared via the two-step method. The internal phase volume fraction of the SMCC-stabilized HIPEs reached as high as 89%. Diverse internal phase volume fractions led to distinct inner structures of foams with closed or open cells. These macroporous polystyrene (PS) foams demonstrated great potential for the effective absorption of organic solvents from underwater. Copyright © 2017 Elsevier Inc. All rights reserved.

On the secondary instability of the most dangerous Goertler vortex

NASA Technical Reports Server (NTRS)

Otto, S. R.; Denier, James P.

1993-01-01

Recent studies have demonstrated the most unstable Goertler vortex mode is found in flows, both two and three-dimensional, with regions of (moderately) large body curvature and these modes reside within a thin layer situated at the base of the conventional boundary layer. Further work concerning the nonlinear development of the most dangerous mode demonstrates that the flow results in a self induced flow reversal. However, prior to the point at which flow reversal is encountered, the total streamwise velocity profile is found to be highly inflectional in nature. Previous work then suggests that the nonlinear vortex state will become unstable to secondary, inviscid, Rayleigh wave instabilities prior to the point of flow reversal. Our concern is with the secondary instability of the nonlinear vortex states, which result from the streamwise evolution of the most unstable Goertler vortex mode, with the aim of determining whether such modes can induce a transition to a fully turbulent state before separation is encountered.

Aircraft Wake Vortex Measurements at Denver International Airport

NASA Technical Reports Server (NTRS)

Dougherty, Robert P.; Wang, Frank Y.; Booth, Earl R.; Watts, Michael E.; Fenichel, Neil; D'Errico, Robert E.

2004-01-01

Airport capacity is constrained, in part, by spacing requirements associated with the wake vortex hazard. NASA's Wake Vortex Avoidance Project has a goal to establish the feasibility of reducing this spacing while maintaining safety. Passive acoustic phased array sensors, if shown to have operational potential, may aid in this effort by detecting and tracking the vortices. During August/September 2003, NASA and the USDOT sponsored a wake acoustics test at the Denver International Airport. The central instrument of the test was a large microphone phased array. This paper describes the test in general terms and gives an overview of the array hardware. It outlines one of the analysis techniques that is being applied to the data and gives sample results. The technique is able to clearly resolve the wake vortices of landing aircraft and measure their separation, height, and sinking rate. These observations permit an indirect estimate of the vortex circulation. The array also provides visualization of the vortex evolution, including the Crow instability.

Computer code for gas-liquid two-phase vortex motions: GLVM

NASA Technical Reports Server (NTRS)

Yeh, T. T.

1986-01-01

A computer program aimed at the phase separation between gas and liquid at zero gravity, induced by vortex motion, is developed. It utilizes an explicit solution method for a set of equations describing rotating gas-liquid flows. The vortex motion is established by a tangential fluid injection. A Lax-Wendroff two-step (McCormack's) numerical scheme is used. The program can be used to study the fluid dynamical behavior of the rotational two-phase fluids in a cylindrical tank. It provides a quick/easy sensitivity test on various parameters and thus provides the guidance for the design and use of actual physical systems for handling two-phase fluids.

Wind tunnel investigation of the interaction and breakdown characteristics of slender wing vortices at subsonic, transonic, and supersonic speeds

NASA Technical Reports Server (NTRS)

Erickson, Gary E.

1991-01-01

The vortex dominated aerodynamic characteristics of a generic 65 degree cropped delta wing model were studied in a wind tunnel at subsonic through supersonic speeds. The lee-side flow fields over the wing-alone configuration and the wing with leading edge extension (LEX) added were observed at M (infinity) equals 0.40 to 1.60 using a laser vapor screen technique. These results were correlated with surface streamline patterns, upper surface static pressure distributions, and six-component forces and moments. The wing-alone exhibited vortex breakdown and asymmetry of the breakdown location at the subsonic and transonic speeds. An earlier onset of vortex breakdown over the wing occurred at transonic speeds due to the interaction of the leading edge vortex with the normal shock wave. The development of a shock wave between the vortex and wing surface caused an early separation of the secondary boundary layer. With the LEX installed, wing vortex breakdown asymmetry did not occur up to the maximum angle of attack in the present test of 24 degrees. The favorable interaction of the LEX vortex with the wing flow field reduced the effects of shock waves on the wing primary and secondary vortical flows. The direct interaction of the wing and LEX vortex cores diminished with increasing Mach number. The maximum attainable vortex-induced pressure signatures were constrained by the vacuum pressure limit at the transonic and supersonic speeds.

Mechanism of transient force augmentation varying with two distinct timescales for interacting vortex rings

NASA Astrophysics Data System (ADS)

Fu, Zhidong; Qin, Suyang; Liu, Hong

2014-01-01

The dynamics of dual vortex ring flows is studied experimentally and numerically in a model system that consists of a piston-cylinder apparatus. The flows are generated by double identical strokes which have the velocity profile characterized by the sinusoidal function of half the period. By calculating the total wake impulse in two strokes in the experiments, it is found that the average propulsive force increases by 50% in the second stroke for the sufficiently small stroke length, compared with the first stroke. In the numerical simulations, two types of transient force augmentation are revealed, there being the transient force augmentation for the small stroke lengths and the absolute transient force augmentation for the large stroke lengths. The relative transient force augmentation increases to 78% for L/D = 1, while the absolute transient force augmentation for L/D = 4 is twice as much as that for L/D = 1. Further investigation demonstrates that the force augmentation is attributed to the interaction between vortex rings, which induces transport of vortex impulse and more evident fluid entrainment. The critical situation of vortex ring separation is defined and indicated, with vortex spacing falling in a narrow gap when the stroke lengths vary. A new model is proposed concerning the limiting process of impulse, further suggesting that apart from vortex formation timescale, vortex spacing should be interpreted as an independent timescale to reflect the dynamics of vortex interaction.

Three Dimensional Compressible Turbulent Flow Computations for a Diffusing S-Duct With/Without Vortex Generators

NASA Technical Reports Server (NTRS)

Cho, Soo-Yong; Greber, Isaac

1994-01-01

Numerical investigations on a diffusing S-duct with/without vortex generators and a straight duct with vortex generators are presented. The investigation consists of solving the full three-dimensional unsteady compressible mass averaged Navier-Stokes equations. An implicit finite volume lower-upper time marching code (RPLUS3D) has been employed and modified. A three-dimensional Baldwin-Lomax turbulence model has been modified in conjunction with the flow physics. A model for the analysis of vortex generators in a fully viscous subsonic internal flow is evaluated. A vortical structure for modeling the shed vortex is used as a source term in the computation domain. The injected vortex paths in the straight duct are compared with the analysis by two kinds of prediction models. The flow structure by the vortex generators are investigated along the duct. Computed results of the flow in a circular diffusing S-duct provide an understanding of the flow structure within a typical engine inlet system. These are compared with the experimental wall static-pressure, static- and total-pressure field, and secondary velocity profiles. Additionally, boundary layer thickness, skin friction values, and velocity profiles in wall coordinates are presented. In order to investigate the effect of vortex generators, various vortex strengths are examined in this study. The total-pressure recovery and distortion coefficients are obtained at the exit of the S-duct. The numerical results clearly depict the interaction between the low velocity flow by the flow separation and the injected vortices.

System and process for efficient separation of biocrudes and water in a hydrothermal liquefaction system

DOEpatents

Elliott, Douglas C.; Hart, Todd R.; Neuenschwander, Gary G.; Oyler, James R.; Rotness, Jr, Leslie J.; Schmidt, Andrew J.; Zacher, Alan H.

2016-08-02

A system and process are described for clean separation of biocrudes and water by-products from hydrothermal liquefaction (HTL) product mixtures of organic and biomass-containing feedstocks at elevated temperatures and pressures. Inorganic compound solids are removed prior to separation of biocrude and water by-product fractions to minimize formation of emulsions that impede separation. Separation may be performed at higher temperatures that reduce heat loss and need to cool product mixtures to ambient. The present invention thus achieves separation efficiencies not achieved in conventional HTL processing.

Vortex scale of unsteady separation on a pitching airfoil.

PubMed

Fuchiwaki, Masaki; Tanaka, Kazuhiro

2002-10-01

The streaklines of unsteady separation on two kinds of pitching airfoils, the NACA65-0910 and a blunt trailing edge airfoil, were studied by dye flow visualization and by the Schlieren method. The latter visualized the discrete vortices shed from the leading edge. The results of these visualization studies allow a comparison between the dynamic behavior of the streakline of unsteady separation and that of the discrete vortices shed from the leading edge. The influence of the airfoil configuration on the flow characteristics was also examined. Furthermore, the scale of a discrete vortex forming the recirculation region was investigated. The non-dimensional pitching rate was k = 0.377, the angle of attack alpha(m) = 16 degrees and the pitching amplitude was fixed to A = +/-6 degrees for Re = 4.0 x 10(3) in this experiment.

A computer program for calculating aerodynamic characteristics of low aspect-ratio wings with partial leading-edge separation

NASA Technical Reports Server (NTRS)

Mehrotra, S. C.; Lan, C. E.

1978-01-01

The necessary information for using a computer program to predict distributed and total aerodynamic characteristics for low aspect ratio wings with partial leading-edge separation is presented. The flow is assumed to be steady and inviscid. The wing boundary condition is formulated by the Quasi-Vortex-Lattice method. The leading edge separated vortices are represented by discrete free vortex elements which are aligned with the local velocity vector at midpoints to satisfy the force free condition. The wake behind the trailing edge is also force free. The flow tangency boundary condition is satisfied on the wing, including the leading and trailing edges. The program is restricted to delta wings with zero thickness and no camber. It is written in FORTRAN language and runs on CDC 6600 computer.

Flows about a rotating circular cylinder by the discrete-vortex method

NASA Astrophysics Data System (ADS)

Kimura, Takeyoshi; Tsutahara, Michihisa

1987-01-01

A numerical study has been conducted for flows past a rotating circular cylinder at high Reynolds numbers, using the discrete-vortex method. It is noted that the reverse Magnus effect is caused by the retreat of the separation point on the acceleration side. At high rotating speed, the nascent vortices of opposite directions are mixed faster, the wake becomes narrower, and predominating frequencies in the lift force disappear.

Vortex- and CO2 -gas-assisted liquid-liquid microextraction with salt addition for the high-performance liquid chromatographic determination of furanic compounds in concentrated juices and dried fruits.

PubMed

Abu-Bakar, Nur-Bahiyah; Makahleh, Ahmad; Saad, Bahruddin

2016-03-01

A novel microextraction method based on vortex- and CO2 -assisted liquid-liquid microextraction with salt addition for the isolation of furanic compounds (5-hydroxymethyl-2-furaldehyde, 5-methyl-2-furaldehyde, 2-furaldehyde, 3-furaldehyde, 2-furoic and 3-furoic acids) was developed. Purging the sample with CO2 was applied after vortexing to enhance the phase separation and mass transfer of the analytes. The optimum extraction conditions were: extraction solvent (volume), propyl acetate (125 μL); sample pH, 2.4; vortexing time, 45 s; salt concentration, 25% w/v and purging time, 5 min. The analytes were separated using an ODS Hypersil C18 column (250×4.6 mm i.d, 5 μm) under gradient flow. The proposed method showed good linearities (r(2) >0.999), low detection limits (0.08-1.9 μg/L) and good recoveries (80.7-122%). The validated method was successfully applied for the determination of the furanic compounds in concentrated juice (mango, date, orange, pomegranate, roselle, mangosteen and soursop) and dried fruit (prune, date and apricot paste) samples. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tracking coherent structures in massively-separated and turbulent flows

NASA Astrophysics Data System (ADS)

Rockwood, Matthew; Huang, Yangzi; Green, Melissa

2018-01-01

Coherent vortex structures are tracked in simulations of massively-separated and turbulent flows. Topological Lagrangian saddle points are found using intersections of the positive and negative finite-time Lyapunov exponent ridges, and these points are then followed in order to track individual coherent structure motion both in a complex interacting three-dimensional flow (turbulent channel) and during vortex formation (two-dimensional bluff body shedding). For a simulation of wall-bounded turbulence in a channel flow, tracking Lagrangian saddles shows that the average structure convection speed exhibits a similar trend as a previously published result based on velocity and pressure correlations, giving validity to the method. When this tracking method is applied in a study of a circular cylinder in cross-flow it shows that Lagrangian saddles rapidly accelerate away from the cylinder surface as the vortex sheds. This saddle behavior is compared with the time-resolved static pressure distribution on the circular cylinder, yielding locations on a cylinder surface where common sensors could detect this phenomenon, which is not available from force measurements or vortex circulation calculations. The current method of tracking coherent structures yields insight into the behavior of the coherent structures in both of the diverse flows presented, highlighting the breadth of its potential application.

Theories of binary fluid mixtures: from phase-separation kinetics to active emulsions

NASA Astrophysics Data System (ADS)

Cates, Michael E.; Tjhung, Elsen

2018-02-01

Binary fluid mixtures are examples of complex fluids whose microstructure and flow are strongly coupled. For pairs of simple fluids, the microstructure consists of droplets or bicontinuous demixed domains and the physics is controlled by the interfaces between these domains. At continuum level, the structure is defined by a composition field whose gradients which are steep near interfaces drive its diffusive current. These gradients also cause thermodynamic stresses which can drive fluid flow. Fluid flow in turn advects the composition field, while thermal noise creates additional random fluxes that allow the system to explore its configuration space and move towards the Boltzmann distribution. This article introduces continuum models of binary fluids, first covering some well-studied areas such as the thermodynamics and kinetics of phase separation, and emulsion stability. We then address cases where one of the fluid components has anisotropic structure at mesoscopic scales creating nematic (or polar) liquid-crystalline order; this can be described through an additional tensor (or vector) order parameter field. We conclude by outlining a thriving area of current research, namely active emulsions, in which one of the binary components consists of living or synthetic material that is continuously converting chemical energy into mechanical work.

On the formation modes in vortex interaction for multiple co-axial co-rotating vortex rings

NASA Astrophysics Data System (ADS)

Qin, Suyang; Liu, Hong; Xiang, Yang

2018-01-01

Interaction among multiple vortices is of particular importance to biological locomotion. It plays an essential role in the force and energy capture. This study examines the motion and dynamics of multiple co-axial co-rotating vortex rings. The vortex rings, which have the same formation time, are successively generated in a piston-cylinder apparatus by accurately controlling the interval time. The flow fields are visualized by the finite-time Lyapunov exponent and then repelling Lagrangian coherent structures (r-LCSs) are determined. Two types of vortex interactions ("strong" and "weak") are defined by investigating the r-LCSs: a strong interaction is indicated by connected r-LCSs showing a channel for fluid transport (termed as a "flux window"); a weak interaction is indicated by disconnected r-LCSs between the vortex rings. For strong interaction, leapfrogging and merger of vortex rings can happen in the later stage of the evolution process; however, the rings are separated for weak interaction. Two distinct formation modes, the formation enhancement mode (FEM) and formation restraint mode (FRM), refer to the effect of one or multiple vortex ring(s) on the initial circulation of the subsequently formed vortex ring. In the FEM, the circulation of a vortex ring is larger than that of an isolated (without interaction) vortex ring. On the other hand, the situation is opposite in the FRM. A dimensionless number reflecting the interaction mechanism, "structure stretching number" S*, is proposed, which evaluates the induced effect of the wake vortices on the formation of a vortex ring. A limiting S* (SL*=(2 ±0.4 ) ×1 0-4) is the bifurcation point of the two formation modes. The augmentation of circulation reaches up to 10% for the FEM when S*SL*), the circulation decreases for at most 20%. The newly defined formation modes and number could shed light on the understanding of the dynamics of multiple vortex ring flows.

Flow structure of vortex-wing interaction

NASA Astrophysics Data System (ADS)

McKenna, Christopher K.

Impingement of a streamwise-oriented vortex upon a fin, tail, blade or wing represents a fundamental class of flow-structure interaction that extends across a range of applications. This interaction can give rise to time-averaged loading, as well as unsteady loading known as buffeting. The loading is sensitive to parameters of the incident vortex as well as the location of vortex impingement on the downstream aerodynamic surface, generically designated as a wing. Particle image velocimetry is employed to determine patterns of velocity, vorticity, swirl ratio, and streamlines on successive cross-flow planes upstream of and along the wing, which lead to volume representations and thereby characterization of the interaction. At locations upstream of the leading edge of the wing, the evolution of the incident vortex is affected by the presence of the wing, and is highly dependent on the spanwise location of vortex impingement. Even at spanwise locations of impingement well outboard of the wing tip, a substantial influence on the structure of the incident vortex at locations significantly upstream of the leading edge of the wing was observed. For spanwise locations close to or intersecting the vortex core, the effects of upstream influence of the wing on the vortex are to: decrease the swirl ratio; increase the streamwise velocity deficit; decrease the streamwise vorticity; increase the azimuthal vorticity; increase the upwash; decrease the downwash; and increase the root-mean-square fluctuations of both streamwise velocity and vorticity. The interrelationship between these effects is addressed, including the rapid attenuation of axial vorticity in presence of an enhanced defect of axial velocity in the central region of the vortex. Moreover, when the incident vortex is aligned with, or inboard of, the tip of the wing, the swirl ratio decreases to values associated with instability of the vortex, giving rise to enhanced values of azimuthal vorticity relative to the streamwise (axial) vorticity, as well as relatively large root-mean-square values of streamwise velocity and vorticity. Along the chord of the wing, the vortex interaction gives rise to distinct modes, which may involve either enhancement or suppression of the vortex generated at the tip of the wing. These modes are classified and interpreted in conjunction with computed modes at the Air Force Research Laboratory. Occurrence of a given mode of interaction is predominantly determined by the dimensionless location of the incident vortex relative to the tip of the wing and is generally insensitive to the Reynolds number and dimensionless circulation of the incident vortex. The genesis of the basic modes of interaction is clarified using streamline topology with associated critical points. Whereas formation of an enhanced tip vortex involves a region of large upwash in conjunction with localized flow separation, complete suppression of the tip vortex is associated with a small-scale separation-attachment bubble bounded by downwash at the wing tip. Oscillation of the wing at an amplitude and velocity nearly two orders of magnitude smaller than the wing chord and free stream velocity respectively can give rise to distinctive patterns of upwash, downwash, and shed vorticity, which are dependent on the outboard displacement of the incident vortex relative to the wing tip. Moreover, these patterns are a strong function of the phase of the wing motion during its oscillation cycle. At a given value of phase, the wing oscillation induces upwash that is reinforced by the upwash of the incident vortex, giving a maximum value of net upwash. Conversely, when these two origins of upwash counteract, rather than reinforce, one another during the oscillation cycle, the net upwash has its minimum value. Analogous interpretations hold for regions of maximum and minimum net downwash located outboard of the regions of upwash. During the oscillation cycle of the wing, the magnitude and scale of the vorticity shed from the tip of the wing are directly correlated with the net upwash, which takes different forms related to the outboard displacement of the incident vortex. As the location of the incident vortex is displaced towards the wing tip, both the maximum upwash and the maximum vorticity of the tip vortex initially increase, then decrease. For the limiting case where the incident vortex impinges directly upon the tip of the wing, there is no tip vortex or induced region of upwash. Furthermore, at small values of vortex displacement from the wing tip, the position of the incident vortex varies significantly from its nominal position during the oscillation cycle. For all locations of the incident vortex, it is shown that, despite the small amplitude of the wing motion, the flow topology is fundamentally different at maximum positive and negative values of the wing velocity, that is, they are not symmetric.

Dynamic mode decomposition of separated flow over a finite blunt plate: time-resolved particle image velocimetry measurements

NASA Astrophysics Data System (ADS)

Liu, Yingzheng; Zhang, Qingshan

2015-07-01

Dynamic mode decomposition (DMD) analysis was performed on a large number of realizations of the separated flow around a finite blunt plate, which were determined by using planar time-resolved particle image velocimetry (TR-PIV). Three plates with different chord-to-thickness ratios corresponding to globally different flow patterns were particularly selected for comparison: L/D = 3.0, 6.0 and 9.0. The main attention was placed on dynamic variations in the dominant events and their interactive influences on the global fluid flow in terms of the DMD analysis. Toward this end, a real-time data transfer from the high-speed camera to the arrayed disks was built to enable continuous sampling of the spatiotemporally varying flows at the frequency of 250 Hz for a long run. The spectra of the wall-normal velocity fluctuation, the energy spectra of the DMD modes, and their spatial patterns convincingly determined the energetic unsteady events, i.e., St = 0.051 (Karman vortex street), 0.109 (harmonic event of Karman vortex street) and 0.197 (leading-edge vortex) in the shortest system L/D = 3.0, St = 0.159 (Karman vortex street) and 0.242 (leading-edge vortex) in the system L/D = 6.0, and St = 0.156 (Karman vortex street) and 0.241 (leading-edge vortex) in the longest system L/D = 9.0. In the shortest system L/D = 3.0, the first DMD mode pattern demonstrated intensified entrainment of the massive fluid above and below the whole plate by the Karman vortex street. The phase-dependent variation in the low-order flow field elucidated that this motion was sustained by the consecutive mechanisms of the convective leading-edge vortices near the upper and lower trailing edges, and the large-scale vortical structures occurring immediately behind the trailing edge, whereas the leading-edge vortices were entrained and decayed into the near wake. For the system L/D = 6.0, the closely approximated energy spectra at St = 0.159 and 0.242 indicated the balanced dominance of dual unsteady events in the measurement region. The Karman vortex street was found to induce considerable localized movement of the fluid near the trailing edges of the plate. However, the leading-edge vortices near the trailing edge were found to detach away from the plate and fully decay around 0.5 D behind the trailing edge, where a well-ordered origination of the downstream large-scale vortical structures (the Karman vortex street) was established and might be locally energized by the decayed leading-edge vortex. In the longest system L/D = 9.0, the phase-dependent variations in the low-order flow disclosed a rapid decay of the leading-edge vortices beyond the reattachment zone, reaching the fully diffused state near the trailing edges. Accordingly, no clear signature of the interaction between the Karman vortex street and the leading-edge vortex could be found in the dynamic process of the leading-edge vortex.

Direct measurement of initial wake separation (bo) and initial circulation (ro) using pulsed lidars

DOT National Transportation Integrated Search

2013-06-17

The initial separation distance (bo) between a counter-rotating vortex pair generated by an aircraft is a fundamental parameter affecting wake turbulence decay. For the past decade Pulsed Doppler Lidars have emerged as the primary remote sensors for ...

Unsteady Separated Flows: Vorticity and Turbulence.

DTIC Science & Technology

1987-04-06

plate, the results are somewhat different . A vortex initiated before : max is obtained in the oscillation cycle yielded convection velocities not...in flat plate m resulted in a 6.25% advance in the cycle where the leading edge vortex was initiated; a value close to that measured using the NACA...three-dimensional model we have used to initiate the three- dimensional study of unsteady flows is a symmetric airfoil (NACA 0015) section fitted witL, a

An improved panel method for the solution of three-dimensional leading edge vortex flows Volume 2: User's guide and programmer's document

NASA Technical Reports Server (NTRS)

Tinoco, E. N.; Lu, P.; Johnson, F. T.

1980-01-01

A computer program developed for solving the subsonic, three dimensional flow over wing-body configurations with leading edge vortex separation is presented. Instructions are given for the proper set up and input of a problem into the computer code. Program input formats and output are described, as well as the overlay structure of the program. The program is written in FORTRAN.

Closed-loop separation control over a sharp edge ramp using genetic programming

NASA Astrophysics Data System (ADS)

Debien, Antoine; von Krbek, Kai A. F. F.; Mazellier, Nicolas; Duriez, Thomas; Cordier, Laurent; Noack, Bernd R.; Abel, Markus W.; Kourta, Azeddine

2016-03-01

We experimentally perform open and closed-loop control of a separating turbulent boundary layer downstream from a sharp edge ramp. The turbulent boundary layer just above the separation point has a Reynolds number Re_{θ }≈ 3500 based on momentum thickness. The goal of the control is to mitigate separation and early re-attachment. The forcing employs a spanwise array of active vortex generators. The flow state is monitored with skin-friction sensors downstream of the actuators. The feedback control law is obtained using model-free genetic programming control (GPC) (Gautier et al. in J Fluid Mech 770:442-457, 2015). The resulting flow is assessed using the momentum coefficient, pressure distribution and skin friction over the ramp and stereo PIV. The PIV yields vector field statistics, e.g. shear layer growth, the back-flow area and vortex region. GPC is benchmarked against the best periodic forcing. While open-loop control achieves separation reduction by locking-on the shedding mode, GPC gives rise to similar benefits by accelerating the shear layer growth. Moreover, GPC uses less actuation energy.

Numerical study of gravity effects on phase separation in a swirl chamber.

PubMed

Hsiao, Chao-Tsung; Ma, Jingsen; Chahine, Georges L

2016-01-01

The effects of gravity on a phase separator are studied numerically using an Eulerian/Lagrangian two-phase flow approach. The separator utilizes high intensity swirl to separate bubbles from the liquid. The two-phase flow enters tangentially a cylindrical swirl chamber and rotate around the cylinder axis. On earth, as the bubbles are captured by the vortex formed inside the swirl chamber due to the centripetal force, they also experience the buoyancy force due to gravity. In a reduced or zero gravity environment buoyancy is reduced or inexistent and capture of the bubbles by the vortex is modified. The present numerical simulations enable study of the relative importance of the acceleration of gravity on the bubble capture by the swirl flow in the separator. In absence of gravity, the bubbles get stratified depending on their sizes, with the larger bubbles entering the core region earlier than the smaller ones. However, in presence of gravity, stratification is more complex as the two acceleration fields - due to gravity and to rotation - compete or combine during the bubble capture.

Experiments on tip vortices interacting with downstream wings

NASA Astrophysics Data System (ADS)

Chen, C.; Wang, Z.; Gursul, I.

2018-05-01

The interaction of meandering tip vortices shed from a leading wing with a downstream wing was investigated experimentally in a water tunnel using flow visualization, particle image velocimetry measurements, and volumetric velocity measurements. Counter-rotating upstream vortices may exhibit sudden variations of the vortex core location when the wing-tip separation is within approximately twice the vortex core radius. This is caused by the formation of vortex dipoles near the wing tip. In contrast, co-rotating upstream vortices do not exhibit such sensitivity. Large spanwise displacement of the trajectory due to the image vortex is possible when the incident vortex is further inboard. For both co-rotating and counter-rotating vortices, as long as there is no direct impingement upon the wing, there is a little change in the structure of the time-averaged vortex past the wing, even though the tip vortex shed from the downstream wing may be substantially weakened or strengthened. In the absence of the downstream wing, as well as for weak interactions, the most energetic unsteady modes represent the first helical mode | m| = 1, which is estimated from the three-dimensional Proper Orthogonal Decomposition modes and has a very large wavelength, on the order of 102 times the vortex core radius, λ/ a = O(102). Instantaneous vorticity measurements as well as flow visualization suggest the existence of a smaller wavelength, λ/ a = 5-6, which is not among the most energetic modes. These two-orders of magnitude different wavelengths are in agreement with the previous measurements of tip vortices and also exhibit qualitative agreement with the transient energy growth analysis. The very long wavelength mode in the upstream vortex may persist during the interaction, and reveal coupling with the trailing vortex as well as increased meandering.

Self-sustaining intense vortices

NASA Astrophysics Data System (ADS)

Carrier, G.; Fendell, F.; Mitchell, J.; Bronstein, M.

1994-10-01

We seek to identify an accessible observable for anticipating tornadogenesis in mesocyclones, because such tornadoes are characterized by exceptionally extended lifespan, exceptionally long and wide path, and exceptionally high wind speed. We associate tornadogenesis with the transition from a one-cell vortex to a two-cell vortex. After such a transition, the core (“eye”) of the vortex consists of virtually nonrotating, slowly recirculating, relatively dry air. Rapidly swirling air swiftly ascends in an annulus (“eyewall”), situated at a small but finite distance from the axis of rotation. The swiftly ascending air is described by a locus of thermodynamic states well approximated by a moist adiabat. Such a transition from a one-cell vortex to a two-cell vortex, on vastly large lateral scale, is known to characterize the intensification of a tropical storm to a typhoon. We adopt a simplified, tractable model for our initial analytic efforts. We examine a quasisteady axisymmetric vortex with a four-part structure, consisting of a bulk potential vortex, a near-ground inflow layer, an “eyewall”, and an “eye”. We inquire under what conditions such a four-part intense vortex, formed in convectively unstable stratified air, is self-sustaining. In particular, we inquire whether the vertical profile of the angular momentum outside of the eyewall is a discriminant for identifying the conditions for which an intense (two-cell) vortex could be self-sustaining. Guidance from laboratory experiments would be helpful concerning the turnaround (the portion of the flow field in which the near-ground swirling inflow separates to form the swirling updraft of the eyewall annulus).

Calculation of vortex lift effect for cambered wings by the suction analogy

NASA Technical Reports Server (NTRS)

Lan, C. E.; Chang, J. F.

1981-01-01

An improved version of Woodward's chord plane aerodynamic panel method for subsonic and supersonic flow is developed for cambered wings exhibiting edge separated vortex flow, including those with leading edge vortex flaps. The exact relation between leading edge thrust and suction force in potential flow is derived. Instead of assuming the rotated suction force to be normal to wing surface at the leading edge, new orientation for the rotated suction force is determined through consideration of the momentum principle. The supersonic suction analogy method is improved by using an effective angle of attack defined through a semi-empirical method. Comparisons of predicted results with available data in subsonic and supersonic flow are presented.

Prediction of vortex shedding from circular and noncircular bodies in supersonic flow

NASA Technical Reports Server (NTRS)

Mendenhall, M. R.; Perkins, S. C., Jr.

1984-01-01

An engineering prediction method and associated computer code NOZVTX to predict nose vortex shedding from circular and noncircular bodies in supersonic flow at angles of attack and roll are presented. The body is represented by either a supersonic panel method for noncircular cross sections or line sources and doublets for circular cross sections, and the lee side vortex wake is modeled by discrete vortices in crossflow planes. The three-dimensional steady flow problem is reduced to a two-dimensional, unsteady, separated flow problem for solution. Comparison of measured and predicted surface pressure distributions, flow field surveys, and aerodynamic characteristics is presented for bodies with circular and noncircular cross-sectional shapes.

Unsteady hydraulic simulation of the cavitating part load vortex rope in Francis turbines

NASA Astrophysics Data System (ADS)

Brammer, J.; Segoufin, C.; Duparchy, F.; Lowys, P. Y.; Favrel, A.; Avellan, F.

2017-04-01

For Francis turbines at part load operation a helical vortex rope is formed due to the swirling nature of the flow exiting the runner. This vortex creates pressure fluctuations which can lead to power swings, and the unsteady loading can lead to fatigue damage of the runner. In the case that the vortex rope cavitates there is the additional risk that hydro-acoustic resonance can occur. It is therefore important to be able to accurately simulate this phenomenon to address these issues. In this paper an unsteady, multi-phase CFD model was used to simulate two part-load operating points, for two different cavitation conditions. The simulation results were validated with test-rig data, and showed very good agreement. These results also served as an input for FEA calculations and fatigue analysis, which are presented in a separate study.

Reduction of vortex induced forces and motion through surface roughness control

DOEpatents

Bernitsas, Michael M; Raghavan, Kamaldev

2014-04-01

Roughness is added to the surface of a bluff body in a relative motion with respect to a fluid. The amount, size, and distribution of roughness on the body surface is controlled passively or actively to modify the flow around the body and subsequently the Vortex Induced Forces and Motion (VIFM). The added roughness, when designed and implemented appropriately, affects in a predetermined way the boundary layer, the separation of the boundary layer, the level of turbulence, the wake, the drag and lift forces, and consequently the Vortex Induced Motion (VIM), and the fluid-structure interaction. The goal of surface roughness control is to decrease/suppress Vortex Induced Forces and Motion. Suppression is required when fluid-structure interaction becomes destructive as in VIM of flexible cylinders or rigid cylinders on elastic support, such as underwater pipelines, marine risers, tubes in heat exchangers, nuclear fuel rods, cooling towers, SPAR offshore platforms.

Unsteady flow past an airfoil pitched at constant rate

NASA Technical Reports Server (NTRS)

Lourenco, L.; Vandommelen, L.; Shib, C.; Krothapalli, A.

1992-01-01

The unsteady flow past a NACA 0012 airfoil that is undertaking a constant-rate pitching up motion is investigated experimentally by the PIDV technique in a water towing tank. The Reynolds number is 5000, based upon the airfoil's chord and the free-stream velocity. The airfoil is pitching impulsively from 0 to 30 deg. with a dimensionless pitch rate alpha of 0.131. Instantaneous velocity and associated vorticity data have been acquired over the entire flow field. The primary vortex dominates the flow behavior after it separates from the leading edge of the airfoil. Complete stall emerges after this vortex detaches from the airfoil and triggers the shedding of a counter-rotating vortex near the trailing edge. A parallel computational study using the discrete vortex, random walk approximation has also been conducted. In general, the computational results agree very well with the experiment.

The growth and breakdown of a vortex-pair in a stably stratified fluid

NASA Astrophysics Data System (ADS)

Advaith, S.; Tinaikar, Aashay; Manu, K. V.; Basu, Saptarshi

2017-11-01

Vortex interaction with density stratification is ubiquitous in nature and applied to various engineering applications. Present study have characterized the spatial and temporal dynamics of the interaction between a vortex and a density stratified interface. The present work is prompted by our research on single tank Thermal Energy Storage (TES) system used in concentrated solar power (CSP) plants where hot and cold fluids are separated by means of density stratification. Rigorous qualitative (High speed Shadowgraph) and quantitative (high speed PIV) studies enable us to have great understanding about vortex formation, propagation, interaction dynamics with density stratified interface, resulted plume characteristics and so on. We have categorized this interaction phenomena in to three different cases based on its nature as non-penetrative, partial penetrative and extensively penetrative. Along with that we have proposed a regime map consisting non-dimensional parameters like Reynolds, Richardson and Atwood numbers which predicts the occurrence above mentioned cases.

Unsteady aerodynamics and vortex-sheet formation of a two-dimensional airfoil

NASA Astrophysics Data System (ADS)

Xia, X.; Mohseni, K.

2017-11-01

Unsteady inviscid flow models of wings and airfoils have been developed to study the aerodynamics of natural and man-made flyers. Vortex methods have been extensively applied to reduce the dimensionality of these aerodynamic models, based on the proper estimation of the strength and distribution of the vortices in the wake. In such modeling approaches, one of the most fundamental questions is how the vortex sheets are generated and released from sharp edges. To determine the formation of the trailing-edge vortex sheet, the classical Kutta condition can be extended to unsteady situations by realizing that a flow cannot turn abruptly around a sharp edge. This condition can be readily applied to a flat plate or an airfoil with cusped trailing edge since the direction of the forming vortex sheet is known to be tangential to the trailing edge. However, for a finite-angle trailing edge, or in the case of flow separation away from a sharp corner, the direction of the forming vortex sheet is ambiguous. To remove any ad-hoc implementation, the unsteady Kutta condition, the conservation of circulation, as well as the conservation laws of mass and momentum are coupled to analytically solve for the angle, strength, and relative velocity of the trailing-edge vortex sheet. The two-dimensional aerodynamic model together with the proposed vortex-sheet formation condition is verified by comparing flow structures and force calculations with experimental results for airfoils in steady and unsteady background flows.

Control and reduction of unsteady pressure loads in separated shock wave turbulent boundary layer interaction

NASA Technical Reports Server (NTRS)

Dolling, David S.; Barter, John W.

1995-01-01

The focus was on developing means of controlling and reducing unsteady pressure loads in separated shock wave turbulent boundary layer interactions. Section 1 describes how vortex generators can be used to effectively reduce loads in compression ramp interaction, while Section 2 focuses on the effects of 'boundary-layer separators' on the same interaction.

Leading-edge flow reattachment and the lateral static stability of low-aspect-ratio rectangular wings

NASA Astrophysics Data System (ADS)

Linehan, Thomas; Mohseni, Kamran

2017-11-01

The relationship between lateral static stability derivative, Clβ,lift coefficient, CL, and angle of attack was investigated for rectangular wings of aspect ratio A R =0.75 ,1 ,1.5 , and 3 using Stereo-Digital Particle Image Velocimetry (S-DPIV) and direct force and moment measurements. When the product Cl βA R is plotted with respect to CL, the lateral stability curves of each wing collapse to a single line for CL<0.7 . For CL>0.7 , the linearity and scaling of Clβwith respect to CL is lost. S-DPIV is used to elucidate the flow physics in this nonlinear regime. At α =10∘ , the leading-edge separation region emerges on the leeward portion of the sideslipped wing by means of vortex shedding. For the A R ≤1.5 wings at α >15∘ , the tip vortex downwash is sufficient to restrict the shedding of leading-edge vorticity thereby sustaining the lift of the leading-edge separation region at high angles of attack. Concurrently, the windward tip vortex grows in size and strength with increasing angle of attack, displacing the leading-edge separation region further toward the leeward wing. This reorganization of lift-generating vorticity results in the initial nonlinearities between Cl β and CL at angles of attack for which CL is still increasing. At angles of attack near that of maximum lift for the A R ≤1 wings, the windward tip vortex lifts off the wing, decreasing the lateral static stability of the wing prior to lift stall. For the A R =3 wing at α >10∘ , nonlinear trends in Cl β versus CL occur due to the spanwise evolution of stalled flow.

Synthesis, Characterization, and Application of High Surface Area, Mesoporous, Stabilized Anatase TiO2 Catalyst Supports

NASA Astrophysics Data System (ADS)

Olsen, Rebecca Elizabeth

Vortex rings constitute the main structure in the wakes of a wide class of swimming and flying animals, as well as in cardiac flows and in the jets generated by some moss and fungi. However, there is a physical limit, determined by an energy maximization principle called the Kelvin-Benjamin principle, to the size that axisymmetric vortex rings can achieve. The existence of this limit is known to lead to the separation of a growing vortex ring from the shear layer feeding it, a process known as `vortex pinch-off', and characterized by the dimensionless vortex formation number. The goal of this thesis is to improve our understanding of vortex pinch-off as it relates to biological propulsion, and to provide future researchers with tools to assist in identifying and predicting pinch-off in biological flows. To this end, we introduce a method for identifying pinch-off in starting jets using the Lagrangian coherent structures in the flow, and apply this criterion to an experimentally-generated starting jet. Since most naturally-occurring vortex rings are not circular, we extend the definition of the vortex formation number to include non-axisymmetric vortex rings, and find that the formation number for moderately non-axisymmetric vortices is similar to that of circular vortex rings. This suggests that naturally-occurring vortex rings may be modeled as axisymmetric vortex rings. Therefore, we consider the perturbation response of the Norbury family of axisymmetric vortex rings. This family is chosen to model vortex rings of increasing thickness and circulation, and their response to prolate shape perturbations is simulated using contour dynamics. Finally, the response of more realistic models for vortex rings, constructed from experimental data using nested contours, to perturbations which resemble those encountered by forming vortices more closely, is simulated using contour dynamics. In both families of models, a change in response analogous to pinch-off is found as members of the family with progressively thicker cores are considered. We posit that this analogy may be exploited to understand and predict pinch-off in complex biological flows, where current methods are not applicable in practice, and criteria based on the properties of vortex rings alone are necessary.

An Investigation of Candidate Sensor-Observable Wake Vortex Strength Parameters for the NASA Aircraft Vortex Spacing System (AVOSS)

NASA Technical Reports Server (NTRS)

Tatnall, Chistopher R.

1998-01-01

The counter-rotating pair of wake vortices shed by flying aircraft can pose a threat to ensuing aircraft, particularly on landing approach. To allow adequate time for the vortices to disperse/decay, landing aircraft are required to maintain certain fixed separation distances. The Aircraft Vortex Spacing System (AVOSS), under development at NASA, is designed to prescribe safe aircraft landing approach separation distances appropriate to the ambient weather conditions. A key component of the AVOSS is a ground sensor, to ensure, safety by making wake observations to verify predicted behavior. This task requires knowledge of a flowfield strength metric which gauges the severity of disturbance an encountering aircraft could potentially experience. Several proposed strength metric concepts are defined and evaluated for various combinations of metric parameters and sensor line-of-sight elevation angles. Representative populations of generating and following aircraft types are selected, and their associated wake flowfields are modeled using various wake geometry definitions. Strength metric candidates are then rated and compared based on the correspondence of their computed values to associated aircraft response values, using basic statistical analyses.

An improved panel method for the solution of three-dimensional leading-edge vortex flows. Volume 1: Theory document

NASA Technical Reports Server (NTRS)

Johnson, F. T.; Lu, P.; Tinoco, E. N.

1980-01-01

An improved panel method for the solution of three dimensional flow and wing and wing-body combinations with leading edge vortex separation is presented. The method employs a three dimensional inviscid flow model in which the configuration, the rolled-up vortex sheets, and the wake are represented by quadratic doublet distributions. The strength of the singularity distribution as well as shape and position of the vortex spirals are computed in an iterative fashion starting with an assumed initial sheet geometry. The method calculates forces and moments as well as detail surface pressure distributions. Improvements include the implementation of improved panel numerics for the purpose of elimination the highly nonlinear effects of ring vortices around double panel edges, and the development of a least squares procedure for damping vortex sheet geometry update instabilities. A complete description of the method is included. A variety of cases generated by the computer program implementing the method are presented which verify the mathematical assumptions of the method and which compare computed results with experimental data to verify the underlying physical assumptions made by the method.

Numerical Modeling Studies of Wake Vortex Transport and Evolution Within the Planetary Boundary Layer

NASA Technical Reports Server (NTRS)

Lin, Yuh-Lang; Arya, S. Pal; Kaplan, Michael L.; Han, Jongil

2000-01-01

The fundamental objective of this research is study behavior of aircraft wake vortices within atmospheric boundary layer (ABL) in support of developing the system, Aircraft VOrtex Spacing System (AVOSS), under NASA's Terminal Area Productivity (TAR) program that will control aircraft spacing within the narrow approach corridors of airports. The purpose of the AVOSS system is to increase airport capacity by providing a safe reduction in separation of aircraft compared to the now-existing flight rules. In our first funding period (7 January 19994 - 6 April 1997), we have accomplished extensive model development and validation of ABL simulations. Using the validated model, in our second funding period (7 April 1997 - 6 April 2000) we have investigated the effects of ambient atmospheric turbulence on vortex decay and descent, Crow instability, and wake vortex interaction with the ground. Recognizing the crucial influence of ABL turbulence on wake vortex behavior, we have also developed a software generating vertical profiles of turbulent kinetic energy (TKE) or energy dissipation rate (EDR), which are, in turn, used as input data in the AVOSS prediction algorithms.

Theoretical and Numerical Studies of a Vortex - Interaction Problem

NASA Astrophysics Data System (ADS)

Hsu, To-Ming

The problem of vortex-airfoil interaction has received considerable interest in the helicopter industry. This phenomenon has been shown to be a major source of noise, vibration, and structural fatigue in helicopter flight. Since unsteady flow is always associated with vortex shedding and movement of free vortices, the problem of vortex-airfoil interaction also serves as a basic building block in unsteady aerodynamics. A careful study of the vortex-airfoil interaction reveals the major effects of the vortices on the generation of unsteady aerodynamic forces, especially the lift. The present work establishes three different flow models to study the vortex-airfoil interaction problem: a theoretical model, an inviscid flow model, and a viscous flow model. In the first two models, a newly developed aerodynamic force theorem has been successfully applied to identify the contributions to unsteady forces from various vortical systems in the flow field. Through viscous flow analysis, different features of laminar interaction, turbulent attached interaction, and turbulent separated interaction are examined. Along with the study of the vortex-airfoil interaction problem, several new schemes are developed for inviscid and viscous flow solutions. New formulas are derived to determine the trailing edge flow conditions, such as flow velocity and direction, in unsteady inviscid flow. A new iteration scheme that is faster for higher Reynolds number is developed for solving the viscous flow problem.

Experimental Study of the Structure of a Wingtip Vortex

NASA Technical Reports Server (NTRS)

Anderson, Elgin A.; Wright, Christopher T.

2000-01-01

A complete look at the near-field development and subsequent role-up of a wingtip vortex from a NACA 0015 wing section is investigated. Two separate but equally important surveys of the vortex structure in the region adjacent to the wingtip and approximately one chord length downstream of the trailing edge are performed. The two surveys provide qualitative flow-visualization an quantitative velocity measurement data. The near-field development and subsequent role-up of the vortex structures is strongly influenced by the angle-of-attack and the end-cap treatment of the wing section. The velocity field near the wingtip of the NACA 0015 wing section was measured with a triple-sensor hot wire probe and compared to flow visualization images produced with titanium tetrachloride smoke injection and laser illumination. The flat end-cap results indicate the formation of multiple, relatively strong vortex structures as opposed to the formation of a single vortex produced with the round end-cap. The multiple vortices generated by the flat end-cap are seen to rotate around a common ce te in a helical pattern until they eventually merge into a single vortex. Compared to a non-dimensional loading parameter, the results of the velocity and flow visualization data shows a "jetlike" axial velocity profile for loading parameter values on the order of 0.1 and a "wakelike" profile for much lower loading parameter values.

Flow Control

DTIC Science & Technology

2013-04-08

fined as p( xs , t), to the flow state which is modeled by the time coefficients of a POD truncation (a fj (t) in equation 17) (Note: the f superscript...spatially to desired flow features (e.g. vortex shedding, vortex pairing, boundary layer growth, separation points, etc.) are chosen and defined as ( xs ...within the numeric simulation. A surface POD analysis, p( xs , t)≃ k ∑ p=1 asp(t)ϕsp( xs ), (30) yields surface POD modes φ sp( xs ). The resulting

Skin friction fields on delta wings

NASA Astrophysics Data System (ADS)

Woodiga, S. A.; Liu, Tianshu

2009-12-01

The normalized skin friction fields on a 65° delta wing and a 76°/40° double-delta wing are measured by using a global luminescent oil-film skin friction meter. The detailed topological structures of skin friction fields on the wings are revealed for different angles of attack and the important features are detected such as reattachment lines, secondary separation lines, vortex bursting and vortex interaction. The comparisons with the existing flow visualization results are discussed.

Vortex Shedding from Finned Circular Cylinders

DTIC Science & Technology

1980-11-01

FINNED CIRCULAR CYLINDERSo ,rm"" 1..UTNOI .)R*., r. *.040, 111SPOR- / T NuMBII f.John G. elute asOHans J.’/, ugt -. . . , ,<-. -. ,:. =., .. Siil P3RPIO...fins and other sharp protuberances. These purely two-dimensional flows then may be used in a strip theory to include at least some aspects of three...boundary- layer theory . Such a prediction method, together with a technique to provide for a vortex sheet at the separation point, will be included in

Investigation of Periodic Pitching through the Static Stall Angle of Attack.

DTIC Science & Technology

1987-03-01

been completed to characterize and predict the dynamic stall process. In 1968 Ham (Ref 11) completed a study to explain the torsional oscillation of...peak values of l.:t and moment could be predicted accurately, but the model did not predict when the peaks would occur. Another problem with the...model was that it required input from experimental results to tell when leading edge vortex separation occurred. The prediction of when vortex shedding

Experimental investigations of on-demand vortex generators

NASA Astrophysics Data System (ADS)

Saddoughi, Seyed G.

1994-12-01

Conventional vortex generators as found on many civil aircrafts are mainly for off-design conditions - e.g. suppression of separation or loss of aileron power when the Mach number accidentally rises above the design (cruise) value. In normal conditions they perform no useful function and exert a significant drag penalty. Recently there have been advances in new designs for passive vortex generators and boundary layer control. While traditionally the generators heights were of the order of the boundary layer thickness (delta), recent advances have been made where generators of the order of delta/4 have been shown to be effective. The advancement of MIcro-Electro-Mechanical (MEM) devices has prompted several efforts in exploring the possibility of using such devices in turbulence control. These new devices offer the possibility of boundary layer manipulation through the production of vortices, momentum jets, or other features in the flow. However, the energy output of each device is low in general, but they can be used in large numbers. Therefore, the possibility of moving from passive vortex generators to active (on-demand) devices becomes of interest. Replacement of fixed rectangular or delta-wing generators by devices that could be activated when needed would produce substantial economies. Our proposed application is not strictly 'active' control: the vortex generators would simply be switched on, all together, when needed (e.g. when the aircraft Mach number exceeded a certain limit). To this extent our scheme is simpler; however, to promote mixing and suppress separation we desire to deposit longitudinal vortices into the outer layer of the boundary layer as in conventional vortex generators. This requires a larger device although an alternative might be an array of smaller devices, for example, a longitudinal row with phase differences in the modulation signals so that the periodic vortices join up. The vortex pair with common flow up has the advantage that it will naturally drift away from the surface, but the disadvantage is that the net vorticity is zero so that the pair is eventually obliterated by turbulent mixing, rather than simply being diffused as in the case of a single vortex. It should be possible to devise alternative shapes of cavity wall so that the jet emerges obliquely and produces net longitudinal vorticity.

Experimental investigations of on-demand vortex generators

NASA Technical Reports Server (NTRS)

Saddoughi, Seyed G.

1994-01-01

Conventional vortex generators as found on many civil aircrafts are mainly for off-design conditions - e.g. suppression of separation or loss of aileron power when the Mach number accidentally rises above the design (cruise) value. In normal conditions they perform no useful function and exert a significant drag penalty. Recently there have been advances in new designs for passive vortex generators and boundary layer control. While traditionally the generators heights were of the order of the boundary layer thickness (delta), recent advances have been made where generators of the order of delta/4 have been shown to be effective. The advancement of MIcro-Electro-Mechanical (MEM) devices has prompted several efforts in exploring the possibility of using such devices in turbulence control. These new devices offer the possibility of boundary layer manipulation through the production of vortices, momentum jets, or other features in the flow. However, the energy output of each device is low in general, but they can be used in large numbers. Therefore, the possibility of moving from passive vortex generators to active (on-demand) devices becomes of interest. Replacement of fixed rectangular or delta-wing generators by devices that could be activated when needed would produce substantial economies. Our proposed application is not strictly 'active' control: the vortex generators would simply be switched on, all together, when needed (e.g. when the aircraft Mach number exceeded a certain limit). To this extent our scheme is simpler; however, to promote mixing and suppress separation we desire to deposit longitudinal vortices into the outer layer of the boundary layer as in conventional vortex generators. This requires a larger device although an alternative might be an array of smaller devices, for example, a longitudinal row with phase differences in the modulation signals so that the periodic vortices join up. The vortex pair with common flow up has the advantage that it will naturally drift away from the surface, but the disadvantage is that the net vorticity is zero so that the pair is eventually obliterated by turbulent mixing, rather than simply being diffused as in the case of a single vortex. It should be possible to devise alternative shapes of cavity wall so that the jet emerges obliquely and produces net longitudinal vorticity.

Nylon 6,6 Nonwoven Fabric Separates Oil Contaminates from Oil-in-Water Emulsions.

PubMed

Ortega, Ryan A; Carter, Erin S; Ortega, Albert E

2016-01-01

Industrial oil spills into aquatic environments can have catastrophic environmental effects. First responders to oil spills along the coast of the Gulf of Mexico in the southern United States have used spunbond nylon fabric bags and fences to separate spilled oil and oil waste from contaminated water. Low area mass density spunbond nylon is capable of sorbing more than 16 times its mass in low viscosity crude oil and more than 26 times its mass in higher viscosity gear lube oil. Nylon bags separated more than 95% of gear lube oil contaminate from a 4.5% oil-in-water emulsion. Field testing of spunbond nylon fences by oil spill first responders has demonstrated the ability of this material to contain the oily contaminate while allowing water to flow through. We hypothesize that the effectiveness of nylon as an oil filter is due to the fact that it is both more oleophilic and more hydrophilic than other commonly used oil separation materials. The nylon traps oil droplets within the fabric or on the surface, while water droplets are free to flow through the fabric to the water on the opposite side of the fabric.

Nylon 6,6 Nonwoven Fabric Separates Oil Contaminates from Oil-in-Water Emulsions

PubMed Central

Carter, Erin S.; Ortega, Albert E.

2016-01-01

Industrial oil spills into aquatic environments can have catastrophic environmental effects. First responders to oil spills along the coast of the Gulf of Mexico in the southern United States have used spunbond nylon fabric bags and fences to separate spilled oil and oil waste from contaminated water. Low area mass density spunbond nylon is capable of sorbing more than 16 times its mass in low viscosity crude oil and more than 26 times its mass in higher viscosity gear lube oil. Nylon bags separated more than 95% of gear lube oil contaminate from a 4.5% oil-in-water emulsion. Field testing of spunbond nylon fences by oil spill first responders has demonstrated the ability of this material to contain the oily contaminate while allowing water to flow through. We hypothesize that the effectiveness of nylon as an oil filter is due to the fact that it is both more oleophilic and more hydrophilic than other commonly used oil separation materials. The nylon traps oil droplets within the fabric or on the surface, while water droplets are free to flow through the fabric to the water on the opposite side of the fabric. PMID:27411088

Method for separating disparate components in a fluid stream

DOEpatents

Meikrantz, David H.

1990-01-01

The invention provides a method of separating a mixed component waste stream in a centrifugal separator. The mixed component waste stream is introduced into the separator and is centrifugally separated within a spinning rotor. A dual vortex separation occurs due to the phase density differences, with the phases exiting the rotor distinct from one another. In a preferred embodiment, aqueous solutions of organics can be separated with up to 100% efficiency. The relatively more dense water phase is centrifugally separated through a radially outer aperture in the separator, while the relatively less dense organic phase is separated through a radially inner aperture.

High Speed Vortex Flows

NASA Technical Reports Server (NTRS)

Wood, Richard M.; Wilcox, Floyd J., Jr.; Bauer, Steven X. S.; Allen, Jerry M.

2000-01-01

A review of the research conducted at the National Aeronautics and Space Administration (NASA), Langley Research Center (LaRC) into high-speed vortex flows during the 1970s, 1980s, and 1990s is presented. The data reviewed is for flat plates, cavities, bodies, missiles, wings, and aircraft. These data are presented and discussed relative to the design of future vehicles. Also presented is a brief historical review of the extensive body of high-speed vortex flow research from the 1940s to the present in order to provide perspective of the NASA LaRC's high-speed research results. Data are presented which show the types of vortex structures which occur at supersonic speeds and the impact of these flow structures to vehicle performance and control is discussed. The data presented shows the presence of both small- and large scale vortex structures for a variety of vehicles, from missiles to transports. For cavities, the data show very complex multiple vortex structures exist at all combinations of cavity depth to length ratios and Mach number. The data for missiles show the existence of very strong interference effects between body and/or fin vortices and the downstream fins. It was shown that these vortex flow interference effects could be both positive and negative. Data are shown which highlights the effect that leading-edge sweep, leading-edge bluntness, wing thickness, location of maximum thickness, and camber has on the aerodynamics of and flow over delta wings. The observed flow fields for delta wings (i.e. separation bubble, classical vortex, vortex with shock, etc.) are discussed in the context of' aircraft design. And data have been shown that indicate that aerodynamic performance improvements are available by considering vortex flows as a primary design feature. Finally a discussing of a design approach for wings which utilize vortex flows for improved aerodynamic performance at supersonic speed is presented.

Experimental evidence of inter-blade cavitation vortex development in Francis turbines at deep part load condition

NASA Astrophysics Data System (ADS)

Yamamoto, K.; Müller, A.; Favrel, A.; Avellan, F.

2017-10-01

Francis turbines are subject to various types of cavitation flow depending on the operating condition. To enable a smooth integration of the renewable energy sources, hydraulic machines are now increasingly required to extend their operating range, especially down to extremely low discharge conditions called deep part load operation. The inter-blade cavitation vortex is a typical cavitation phenomenon observed at deep part load operation. However, its dynamic characteristics are insufficiently understood today. In an objective of revealing its characteristics, the present study introduces a novel visualization technique with instrumented guide vanes embedding the visualization devices, providing unprecedented views on the inter-blade cavitation vortex. The binary image processing technique enables the successful evaluation of the inter-blade cavitation vortex in the images. As a result, it is shown that the probability of the inter-blade cavitation development is significantly high close to the runner hub. Furthermore, the mean vortex line is calculated and the vortex region is estimated in the three-dimensional domain for the comparison with numerical simulation results. In addition, the on-board pressure measurements on a runner blade is conducted, and the influence of the inter-blade vortex on the pressure field is investigated. The analysis suggests that the presence of the inter-blade vortex can magnify the amplitude of pressure fluctuations especially on the blade suction side. Furthermore, the wall pressure difference between pressure and suction sides of the blade features partially low or negative values near the hub at the discharge region where the inter-blade vortex develops. This negative pressure difference on the blade wall suggests the development of a backflow region caused by the flow separation near the hub, which is closely related to the development of the inter-blade vortex. The development of the backflow region is confirmed by the numerical simulation, and the physical mechanisms of the inter-blade vortex development is, furthermore, discussed.

Three-dimensional boundary layers approaching separation

NASA Technical Reports Server (NTRS)

Williams, J. C., III

1976-01-01

The theory of semi-similar solutions of the laminar boundary layer equations is applied to several flows in which the boundary layer approaches a three-dimensional separation line. The solutions obtained are used to deduce the nature of three-dimensional separation. It is shown that in these cases separation is of the "ordinary" type. A solution is also presented for a case in which a vortex is embedded within the three-dimensional boundary layer.

Minnowbrook VI: 2009 Workshop on Flow Physics and Control for Internal and External Aerodynamics

NASA Technical Reports Server (NTRS)

LaGraff, John E.; Povinelli, Louis A.; Gostelow, J. Paul; Glauser, Mark

2010-01-01

Topics covered include: Flow Physics and control for Internal and External Aerodynamics (not in TOC...starts on pg13); Breaking CFD Bottlenecks in Gas-Turbine Flow-Path Design; Streamwise Vortices on the Convex Surfaces of Circular Cylinders and Turbomachinery Blading; DNS and Embedded DNS as Tools for Investigating Unsteady Heat Transfer Phenomena in Turbines; Cavitation, Flow Structure and Turbulence in the Tip Region of a Rotor Blade; Development and Application of Plasma Actuators for Active Control of High-Speed and High Reynolds Number Flows; Active Flow Control of Lifting Surface With Flap-Current Activities and Future Directions; Closed-Loop Control of Vortex Formation in Separated Flows; Global Instability on Laminar Separation Bubbles-Revisited; Very Large-Scale Motions in Smooth and Rough Wall Boundary Layers; Instability of a Supersonic Boundary-Layer With Localized Roughness; Active Control of Open Cavities; Amplitude Scaling of Active Separation Control; U.S. Air Force Research Laboratory's Need for Flow Physics and Control With Applications Involving Aero-Optics and Weapon Bay Cavities; Some Issues Related to Integrating Active Flow Control With Flight Control; Active Flow Control Strategies Using Surface Pressure Measurements; Reduction of Unsteady Forcing in a Vaned, Contra-Rotating Transonic Turbine Configuration; Active Flow Control Stator With Coanda Surface; Controlling Separation in Turbomachines; Flow Control on Low-Pressure Turbine Airfoils Using Vortex Generator Jets; Reduced Order Modeling Incompressible Flows; Study and Control of Flow Past Disk, and Circular and Rectangular Cylinders Aligned in the Flow; Periodic Forcing of a Turbulent Axisymmetric Wake; Control of Vortex Breakdown in Critical Swirl Regime Using Azimuthal Forcing; External and Turbomachinery Flow Control Working Group; Boundary Layers, Transitions and Separation; Efficiency Considerations in Low Pressure Turbines; Summary of Conference; and Final Plenary Session Transcript.

Application of D-optimal experimental design method to optimize the formulation of O/W cosmetic emulsions.

PubMed

Djuris, J; Vasiljevic, D; Jokic, S; Ibric, S

2014-02-01

This study investigates the application of D-optimal mixture experimental design in optimization of O/W cosmetic emulsions. Cetearyl glucoside was used as a natural, biodegradable non-ionic emulsifier in the relatively low concentration (1%), and the mixture of co-emulsifiers (stearic acid, cetyl alcohol, stearyl alcohol and glyceryl stearate) was used to stabilize the formulations. To determine the optimal composition of co-emulsifiers mixture, D-optimal mixture experimental design was used. Prepared emulsions were characterized with rheological measurements, centrifugation test, specific conductivity and pH value measurements. All prepared samples appeared as white and homogenous creams, except for one homogenous and viscous lotion co-stabilized by stearic acid alone. Centrifugation testing revealed some phase separation only in the case of sample co-stabilized using glyceryl stearate alone. The obtained pH values indicated that all samples expressed mild acid value acceptable for cosmetic preparations. Specific conductivity values are attributed to the multiple phases O/W emulsions with high percentages of fixed water. Results of the rheological measurements have shown that the investigated samples exhibited non-Newtonian thixotropic behaviour. To determine the influence of each of the co-emulsifiers on emulsions properties, the obtained results were evaluated by the means of statistical analysis (ANOVA test). On the basis of comparison of statistical parameters for each of the studied responses, mixture reduced quadratic model was selected over the linear model implying that interactions between co-emulsifiers play the significant role in overall influence of co-emulsifiers on emulsions properties. Glyceryl stearate was found to be the dominant co-emulsifier affecting emulsions properties. Interactions between the glyceryl stearate and other co-emulsifiers were also found to significantly influence emulsions properties. These findings are especially important as they can be used for development of the product that meets users' requirements, as represented in the study. © 2013 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

The therapeutic effect of nano-encapsulated and nano-emulsion forms of carvacrol on experimental liver fibrosis.

PubMed

Hussein, Jihan; El-Banna, Mona; Mahmoud, Khaled F; Morsy, Safaa; Abdel Latif, Yasmin; Medhat, Dalia; Refaat, Eman; Farrag, Abdel Razik; El-Daly, Sherien M

2017-06-01

The present study aimed to compare the therapeutic efficiency of nano-encapsulated and nano-emulsion carvacrol administration on liver injury in thioacetamide (TAA) treated rats. To fulfill our target, we used sixty male albino rats classified into six groups as follow: control, nano-encapsulated carvacrol, nano-emulsion carvacrol, thioacetamide, treated nano-encapsulated carvacrol and treated nano-emulsion carvacrol groups. Blood samples were collected from all groups and the separated serum was used for analysis of the following biochemical parameters; aspartate aminotransferase (AST), alanine aminotransferase (ALT), S100 B protein, alpha fetoprotein (AFP) and caspase-3. The levels of malondialdehyde (MDA), reduced glutathione (GSH), nitric oxide (NO), monocyte chemoattractant protein-1(MCP-1) and hydroxyproline content were all evaluated in liver tissue homogenate. Histopathological examinations for liver tissues were also performed. Thioacetamide induced hepatic damage in rats as revealed by the significant increase in the levels of serum ALT, AST and produced oxidative stress as displayed by the significant elevation in the levels of hepatic MDA and NO concomitant with a significant decrease in GSH. In addition, thioacetamide significantly increased serum S100B protein, alpha fetoprotein and caspase-3 along with hepatic MCP-1 and hydroxyproline; these results were confirmed by the histopathological investigation. In contrast, nano-encapsulated and nano-emulsion carvacrol were able to ameliorate these negative changes in the thioacetamide injected rats. However, the effect of the nano-encapsulated form of carvacrol was more prominent than the nano-emulsion form. Nano-encapsulated and nano-emulsion carvacrol can ameliorate thioacetamide induced liver injury. These results could be attributed to the potential anti-inflammatory, antioxidant, and anti-apoptotic activities of carvacrol in addition to the effectiveness of the encapsulation technique that can protect carvacrol structure and increase its efficiency and stability. Moreover, nano-encapsulation of carvacrol is more efficient than nano-emulsion. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Electric field mediated breakdown of thin liquid films separating microscopic emulsion droplets

NASA Astrophysics Data System (ADS)

Mostowfi, Farshid; Khristov, Khristo; Czarnecki, Jan; Masliyah, Jacob; Bhattacharjee, Subir

2007-04-01

The authors present a microfluidic technique for electrically induced breakup of thin films formed between microscopic emulsion droplets. The method involves creating a stationary film at the intersection of two microchannels etched onto a glass substrate. After stabilizing the film, a ramped potential is applied across it. The electrical stresses developed at the film interfaces lead to its rupture above a threshold potential. The potential difference at which the film ruptures assesses the film stability. This approach is employed to demonstrate how surfactant (lecithin) adsorption imparts stability to an ultrathin oil film formed between two water droplets.

Light-Triggered CO2 Breathing Foam via Nonsurfactant High Internal Phase Emulsion.

PubMed

Zhang, Shiming; Wang, Dingguan; Pan, Qianhao; Gui, Qinyuan; Liao, Shenglong; Wang, Yapei

2017-10-04

Solid materials for CO 2 capture and storage have attracted enormous attention for gaseous separation, environmental protection, and climate governance. However, their preparation and recovery meet the problems of high energy and financial cost. Herein, a controllable CO 2 capture and storage process is accomplished in an emulsion-templated polymer foam, in which CO 2 is breathed-in under dark and breathed-out under light illumination. Such a process is likely to become a relay of natural CO 2 capture by plants that on the contrary breathe out CO 2 at night. Recyclable CO 2 capture at room temperature and release under light irradiation guarantee its convenient and cost-effective regeneration in industry. Furthermore, CO 2 mixed with CH 4 is successfully separated through this reversible breathing in and out system, which offers great promise for CO 2 enrichment and practical methane purification.

Correlation of individual cosmic ray nuclei with the observation of light flashes by Apollo astronauts. [nuclear emulsion detector design and operation

NASA Technical Reports Server (NTRS)

Pinsky, L. S.; Osborne, W. Z.; Bailey, J. V.

1975-01-01

A nuclear emulsion detector known as the Apollo Light Flash Moving Emulsion Detector (ALFMED) was designed: (1) to record tracks of primary cosmic rays; (2) to provide time-of-passage information via a relative plate translation technique; (3) to provide particle trajectory information; and (4) to fit into a masklike device that could be located about the head and eyes of an astronaut. An ALFMED device was worn by an astronaut observing light flashes for 60 minutes on each of the last two Apollo missions. During the Apollo 17 experiment seventeen separate flashes were reported by the observer. With one-third of the total plate area completely analyzed, two definite correlations have been found between Z greater than 8 cosmic ray nuclei traversing an eye and the reports of visual sensations.

Synthesis of mesoporous poly(melamine-formaldehyde) particles by inverse emulsion polymerization.

PubMed

Schwarz, Dana; Weber, Jens

2017-07-15

Mesoporous poly(melamine-formaldehyde) (MF) particles with surface areas of up to 200m 2 g -1 were synthesized by an inverse emulsion polymerization using dodecane and Span80® as continuous phase. The finer details of the shape control (using emulsion techniques) and the porosity control (using silica nanoparticles as hard-template) are discussed. The impact of phase-separation processes on the observable porosity of the 20-200µm sized spherical particles is analysed by gas sorption methods and electron microscopy. The high density of amine and triazine functional groups in the porous MF particles make the material a promising adsorber for heavy metal ions and methylene blue. In a preliminary column experiment, the synthesized material exhibited a total capacity of 2.54mmol/g (≙ 812.4mg/g) for the adsorption of methylene blue. Copyright © 2017 Elsevier Inc. All rights reserved.

Magnetic vortex nucleation/annihilation in artificial-ferrimagnet microdisks

DOE PAGES

Lapa, Pavel N.; Ding, Junjia; Phatak, Charudatta; ...

2017-08-28

The topological nature of magnetic-vortex state gives rise to peculiar magnetization reversal observed in magnetic microdisks. Interestingly, magnetostatic and exchange energies which drive this reversal can be effectively controlled in artificial ferrimagnet heterostructures composed of rare-earth and transition metals. [Py(t)/Gd(t)] 25 (t=1 or 2 nm) superlattices demonstrate a pronounced change of the magnetization and exchange stiffness in a 10–300 K temperature range as well as very small magnetic anisotropy. Due to these properties, the magnetization of cylindrical microdisks composed of these artificial ferrimagnets can be transformed from the vortex to uniformly-magnetized states in a permanent magnetic field by changing themore » temperature. We explored the behavior of magnetization in 1.5-µm [Py(t)/Gd(t)] 25 (t=1 or 2 nm) disks at different temperatures and magnetic fields and observed that due to the energy barrier separating vortex and uniformly-magnetized states, the vortex nucleation and annihilation occur at different temperatures. This causes the temperature dependences of the Py/Gd disks magnetization to demonstrate unique hysteretic behavior in a narrow temperature range. It was discovered that for the [Py(2 nm)/Gd(2 nm)] 25 microdisks the vortex can be metastable at a certain temperature range.« less

Magnetic vortex nucleation/annihilation in artificial-ferrimagnet microdisks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lapa, Pavel N.; Ding, Junjia; Phatak, Charudatta

The topological nature of magnetic-vortex state gives rise to peculiar magnetization reversal observed in magnetic microdisks. Interestingly, magnetostatic and exchange energies which drive this reversal can be effectively controlled in artificial ferrimagnet heterostructures composed of rare-earth and transition metals. [Py(t)/Gd(t)] 25 (t=1 or 2 nm) superlattices demonstrate a pronounced change of the magnetization and exchange stiffness in a 10–300 K temperature range as well as very small magnetic anisotropy. Due to these properties, the magnetization of cylindrical microdisks composed of these artificial ferrimagnets can be transformed from the vortex to uniformly-magnetized states in a permanent magnetic field by changing themore » temperature. We explored the behavior of magnetization in 1.5-µm [Py(t)/Gd(t)] 25 (t=1 or 2 nm) disks at different temperatures and magnetic fields and observed that due to the energy barrier separating vortex and uniformly-magnetized states, the vortex nucleation and annihilation occur at different temperatures. This causes the temperature dependences of the Py/Gd disks magnetization to demonstrate unique hysteretic behavior in a narrow temperature range. It was discovered that for the [Py(2 nm)/Gd(2 nm)] 25 microdisks the vortex can be metastable at a certain temperature range.« less

Computational Fluid Dynamics (CFD) simulations of a Heisenberg Vortex Tube

NASA Astrophysics Data System (ADS)

Bunge, Carl; Sitaraman, Hariswaran; Leachman, Jake

2017-11-01

A 3D Computational Fluid Dynamics (CFD) simulation of a Heisenberg Vortex Tube (HVT) is performed to estimate cooling potential with cryogenic hydrogen. The main mechanism driving operation of the vortex tube is the use of fluid power for enthalpy streaming in a highly turbulent swirl in a dual-outlet tube. This enthalpy streaming creates a temperature separation between the outer and inner regions of the flow. Use of a catalyst on the peripheral wall of the centrifuge enables endothermic conversion of para-ortho hydrogen to aid primary cooling. A κ- ɛ turbulence model is used with a cryogenic, non-ideal equation of state, and para-orthohydrogen species evolution. The simulations are validated with experiments and strategies for parametric optimization of this device are presented.

Spiral Transformation for High-Resolution and Efficient Sorting of Optical Vortex Modes.

PubMed

Wen, Yuanhui; Chremmos, Ioannis; Chen, Yujie; Zhu, Jiangbo; Zhang, Yanfeng; Yu, Siyuan

2018-05-11

Mode sorting is an essential function for optical multiplexing systems that exploit the orthogonality of the orbital angular momentum mode space. The familiar log-polar optical transformation provides a simple yet efficient approach whose resolution is, however, restricted by a considerable overlap between adjacent modes resulting from the limited excursion of the phase along a complete circle around the optical vortex axis. We propose and experimentally verify a new optical transformation that maps spirals (instead of concentric circles) to parallel lines. As the phase excursion along a spiral in the wave front of an optical vortex is theoretically unlimited, this new optical transformation can separate orbital angular momentum modes with superior resolution while maintaining unity efficiency.

Spiral Transformation for High-Resolution and Efficient Sorting of Optical Vortex Modes

NASA Astrophysics Data System (ADS)

Wen, Yuanhui; Chremmos, Ioannis; Chen, Yujie; Zhu, Jiangbo; Zhang, Yanfeng; Yu, Siyuan

2018-05-01

Mode sorting is an essential function for optical multiplexing systems that exploit the orthogonality of the orbital angular momentum mode space. The familiar log-polar optical transformation provides a simple yet efficient approach whose resolution is, however, restricted by a considerable overlap between adjacent modes resulting from the limited excursion of the phase along a complete circle around the optical vortex axis. We propose and experimentally verify a new optical transformation that maps spirals (instead of concentric circles) to parallel lines. As the phase excursion along a spiral in the wave front of an optical vortex is theoretically unlimited, this new optical transformation can separate orbital angular momentum modes with superior resolution while maintaining unity efficiency.

Prediction of subsonic vortex shedding from forebodies with chines

NASA Technical Reports Server (NTRS)

Mendenhall, Michael R.; Lesieutre, Daniel J.

1990-01-01

An engineering prediction method and associated computer code VTXCHN to predict nose vortex shedding from circular and noncircular forebodies with sharp chine edges in subsonic flow at angles of attack and roll are presented. Axisymmetric bodies are represented by point sources and doublets, and noncircular cross sections are transformed to a circle by either analytical or numerical conformal transformations. The lee side vortex wake is modeled by discrete vortices in crossflow planes along the body; thus the three-dimensional steady flow problem is reduced to a two-dimensional, unsteady, separated flow problem for solution. Comparison of measured and predicted surface pressure distributions, flow field surveys, and aerodynamic characteristics are presented for noncircular bodies alone and forebodies with sharp chines.

Simulation of moving flat plate with unsteady translational motion using vortex method

NASA Astrophysics Data System (ADS)

Widodo, A. F.; Zuhal, L. R.

2013-10-01

This paper presents simulation of moving flate plate with unsteady translational motion using Lagrangianmeshless numerical simulation named vortex method. The method solves Navier-Stokes equations in term of vorticity. The solving strategy is splitting the equation into diffusion and convection term to be solved separately. The diffusion term is modeled by particles strength exchange(PSE) which is the most accurate of diffusion modeling in vortex method. The convection term that represents transport of particles is calculated by time step integration of velocity. Velocity of particles is natively calculated using Biot-Savart relation but for acceleration, fastmultiple method(FMM) is employed. The simulation is validated experimentally using digital particle image velocimetry(DPIV) and the results give good agreement.

Separation and characterization of effective demulsifying substances from surface of Alcaligenes sp. S-XJ-1 and its application in water-in-kerosene emulsion.

PubMed

Huang, Xiangfeng; Peng, Kaiming; Feng, Yi; Liu, Jia; Lu, Lijun

2013-07-01

The main goal of this work was to analyze the effect of surface substances on demulsifying capability of the demulsifying strain Alcaligenes sp. S-XJ-1. The demulsifying substances were successfully separated from the cell surface with dichloromethane-alkali treatment, and exhibited 67.5% of the demulsification ratio for water-in-kerosene emulsions at a dosage of 356mg/L. FT-IR, TLC and ESI-MS analysis confirmed the presence of a carbohydrate-protein-lipid complex in the demulsifying substances with the major molecular ions from mass-to-charge ratio (m/z) 165 to 814. After the substances separated, the cell morphology changed from aggregated to dispersed, and the concentration of cell surface functional groups decreased. Cell surface hydrophobicity and the ability of cell adhesion to hydrophobic surface of the treated cells was also reduced compared with original cell. It was proved that the demulsifying substances had a significant effect on cell surface properties and accordingly with demulsifying capability of Alcaligenes sp. S-XJ-1. Copyright © 2013 Elsevier Ltd. All rights reserved.

On vortex bursting

NASA Technical Reports Server (NTRS)

Werle, H.

1984-01-01

Vortex bursting is studied by means of visualization. The physical behavior of the phenomenon is emphasized, and its similarity with boundary layer separation or wake bursting becomes apparent. The essential influence of an increasing pressure gradient on the initiation, the position and the type of bursting is clearly confirmed. The evolution of the phenomena as a function of several parameters is analyzed in the case of delta wings, alone or installed on aircraft models, and compared with the results of similar wind tunnel or flight tests.

Aircraft Wake Vortices: An Annotated Bibliography (1923-1990)

DTIC Science & Technology

1991-01-01

Generated by Large Jet- Transport Aircraft; (2) Results of the Boeing Company Wake Turbulence Test Program; (3) Meas"’rements of the Vortex Wake...Administration and the Boeing Company . The objective was to update the interim air traffic separation standards issued on 21 January 1970 restricting the airspace...VORTEX TI<AN; I ORT AN) COMPARI.SON WITI EXI’ER I M ENT," FAA-RD-74-74. [ and 74.11, April 19/4, Lockheed Missiles & Space Company , Hlintsvi lie, A,. A

VORCAM: A computer program for calculating vortex lift effect of cambered wings by the suction analogy

NASA Technical Reports Server (NTRS)

Lan, C. E.; Chang, J. F.

1981-01-01

A user's guide to an improved version of Woodward's chord plane aerodynamic panel computer code is presumed. The guide can be applied to cambered wings exhibiting edge separated flow, including those with leading edge vortex flow at subsonic and supersonic speeds. New orientations for the rotated suction force are employed based on the momentum principal. The supersonic suction analogy method is improved by using an effective angle of attack defined through a semiempirical method.

Aerodynamics of wings at low Reynolds numbers: Boundary layer separation and reattachment

NASA Astrophysics Data System (ADS)

McArthur, John

Due to advances in electronics technology, it is now possible to build small scale flying and swimming vehicles. These vehicles will have size and velocity scales similar to small birds and fish, and their characteristic Reynolds number will be between 104 and 105. Currently, these flying and swimming vehicles do not perform well, and very little research has been done to characterize them, or to explain why they perform so poorly. This dissertation documents three basic investigations into the performance of small scale lifting surfaces, with Reynolds numbers near 104. Part I. Low Reynolds number aerodynamics. Three airfoil shapes were studied at Reynolds numbers of 1 and 2x104: a flat plate airfoil, a circular arc cambered airfoil, and the Eppler 387 airfoil. Lift and drag force measurements were made on both 2D and 3D conditions, with the 3D wings having an aspect ratio of 6, and the 2D condition being approximated by placing end plates at the wing tips. Comparisons to the limited number of previous measurements show adequate agreement. Previous studies have been inconclusive on whether lifting line theory can be applied to this range of Re, but this study shows that lifting line theory can be applied when there are no sudden changes in the slope of the force curves. This is highly dependent on the airfoil shape of the wing, and explains why previous studies have been inconclusive. Part II. The laminar separation bubble. The Eppler 387 airfoil was studied at two higher Reynolds numbers: 3 and 6x10 4. Previous studies at a Reynolds number of 6x104 had shown this airfoil experiences a drag increase at moderate lift, and a subsequent drag decrease at high lift. Previous studies suggested that the drag increase is caused by a laminar separation bubble, but the experiments used to show this were conducted at higher Reynolds numbers and extrapolated down. Force measurements were combined with flow field measurements at Reynolds numbers 3 and 6x104 to determine whether the drag increase is really caused by the formation of a laminar separation bubble. The results clearly indicate that the reverse is true, and that the subsequent drag decrease is caused by the laminar separation bubble. Part III. The leading edge vortex. Four wings with different sweep angles were studied at Reynolds number 5x104: sweep angles of 0, 20, 40, and 60 degrees. The wings had a simple cambered plate airfoil similar to the cambered airfoil of part I above. Each wing was built to have the same aspect ratio, wing area, and streamwise airfoil shape. Previous studies on bird wings speculate that simply sweeping the wings can cause a leading edge vortex to form, which could cause substantial improvements in performance. However, these studies were not well controlled, and were conducted from a biological perspective. Qualitative and quantitative flow field measurements were combined with force measurements to conduct a well controlled engineering experiment on the formation and effect of a leading edge vortex on simple swept wings. A stable vortex was found to form over the 60 degree swept wing at one particular angle of attack, but it was not similar to the traditional notion of a leading edge vortex. The vortex has a small radius, and extends over little of the span. Force measurements indicate that the vortex has no significant impact on the forces measured. Thus, simply sweeping a wing is not sufficient to form a significant leading edge vortex, and other effects must be considered.

Showing Emulsion Properties with Common Dairy Foods

NASA Astrophysics Data System (ADS)

Bravo-Diaz, Carlos; Gonzalez-Romero, Elisa

1996-09-01

Foods are mixtures of different chemical compounds, and the quality we sense (taste, texture, color, etc.) are all manifestations of its chemical properties. Some of them can be visualized with the aid of simple, safe and inexpensive experiments using dairy products that can be found in any kitchen and using almost exclusively kitchen utensils. In this paper we propose some of them related with food emulsions. Food emulsions cover an extremely wide area of daily-life applications such as milk, sauces, dressings and beverages. Experimentation with some culinary recipes to prepare them and the analyisis of the observed results is close to ideal subject for the introduction of chemical principles, allowing to discuss about the nature and composition of foods, the effects of additives, etc. At the same time it allows to get insights into the scientific reasons that underlie on the recipes (something that it is not usually found in most cookbooks). For example, when making an emulsion like mayonnaise, why the egg yolks and water are the first materials in the bowl , and the oil is added to them rather than in the other way around? How you can "rescue" separate emulsions (mayonnaise)? Which parameters affect emulsion stability? Since safety, in its broad sense, is the first requisite for any food, concerns about food exist throughout the world and the more we are aware of our everyday life, the more likely we will be to deal productively with the consequences. On the other hand, understanding what foods are and how cooking works destroys no delightful mystery of the art of cuisine, instead the mystery expands.

Separation control in a hypersonic shock wave / turbulent boundary-layer interaction

NASA Astrophysics Data System (ADS)

Schreyer, Anne-Marie; Bermejo-Moreno, Ivan; Kim, Jeonglae; Urzay, Javier

2016-11-01

Hypersonic vehicles play a key role for affordable access to space. The associated flow fields are strongly affected by shock wave/turbulent boundary-layer interactions, and the inherent separation causes flow distortion and low-frequency unsteadiness. Microramp sub-boundary layer vortex generators are a promising means to control separation and diminish associated detrimental effects. We investigate the effect of a microramp on the low-frequency unsteadiness in a fully separated interaction. A large eddy simulation of a 33 ∘ -compression-ramp interaction was performed for an inflow Mach number of 7.2 and a Reynolds number based on momentum thickness of Reθ = 3500 , matching the experiment of Schreyer et al. (2011). For the control case, we introduced a counter-rotating vortex pair, as induced by a single microramp, into the boundary layer through the inflow conditions. We applied a dynamic mode decomposition (DMD) on both cases to identify coherent structures that are responsible for the dynamic behavior. Based on the DMD, we discuss the reduction of the separation zone and the stabilization of the shock motion achieved by the microramp, and contribute to the description of the governing mechanisms. Pursued during the 2016 CTR Summer Program at Stanford University.

Inertial instabilities in a mixing-separating microfluidic device

NASA Astrophysics Data System (ADS)

Domingues, Allysson; Poole, Robert; Dennis, David

2017-11-01

Combining and separating fluids has many industrial and biomedical applications. This numerical and experimental study explores inertial instabilities in a so-called mixing-separating cell micro-geometry which could potentiality be used to enhance mixing. Our microfluidic mixing-separating cell consists of two straight square parallel channels with flow from opposite directions with a central gap that allows the streams to interact, mix or remain separate (often referred to as the `H' geometry). A stagnation point is generated at the centre of symmetry due to the two opposed inlets and outlets. Under creeping flow conditions (Reynolds number [ Re 0 ]) the flow is steady, two-dimensional and produces a sharp symmetric boundary between fluids stream entering the geometry from opposite directions. For Re > 30 , an inertial instability appears which leads to the generation of a central vortex and the breaking of symmetry, although the flow remains steady. As Re increases the central vortex divides into two vortices. Our experimental and numerical investigations both show the same phenomena. The results suggest that the effect observed can be exploited to enhance mixing in biomedical or other applications. Work supported by CNPq Grant 203195/2014-0.

Synthetic Polymers at Interfaces: Monodisperse Emulsions Multiple Emulsions and Liquid Marbles

NASA Astrophysics Data System (ADS)

Sun, Guanqing

The adsorption of polymeric materials at interfaces is an energetically favorable process which is investigated in much diversified fields, such as emulsions, bubbles, foams, liquid marbles. Pickering emulsion, which is emulsion stabilized by solid particles has been investigated for over one century and preparation of Pickering emulsion with narrow size distribution is crucial for both the theoretical study of the stabilization mechanism and practical application, such as templated fabrication of colloidosomes. The precise control over the size and functionality of polymer latices allows the preparation of monodisperse Pickering emulsions with desired sizes through SPG membrane emulsification at rather rapid rate compared to microfludic production. Double or multiple emulsions have long been investigated but its rapid destabilization has always been a major obstacle in applying them into practical applications. The modern living polymerization techniques allow us to prepare polymers with designed structure of block copolymers which makes it possible to prepare ultra-stable multiple emulsions. The precise tuning of the ratio of hydrophobic part over the hydrophilic can unveil the stabilization mechanism. Liquid marble is a new type of materials of which liquid droplets are coated by dry particles. The coating of an outer layer of dry particles renders the liquid droplets non-sticky at solid surface which is useful in transportation of small amount of liquid without leakage at extreme low friction force. The property of liquid marbles relies largely on the stabilizers and the drying condition of polymeric latices is shown to have great influence on the property of liquid marbles. Firstly, an introduction to the interfacial and colloidal science with special attention to topics on emulsions, multiple emulsion and liquid marbles is given in Chapter 1. The unique features of an interface and a discussion on the definition of colloids are introduced prior to the discussion of emulsion stabilization and preparation. A historical review of multiple emulsions is presented subsequently and the stability mechanism is discussed in details with regard to the transportation kinetics of small molecules through the separating membrane of double emulsions. The principle, property and applications of liquid marbles are then summarized. Secondly, the preparation of monodisperse Pickering emulsions stabilized by soft PNIPAM-co-MAA microgels through SPG membrane emulsification is described. The influence of the membrane pore size, pH of the particle dispersion, particle size and the operating parameters of the membrane emulsification device on the size of the emulsion droplets was investigated systematically. The improvement in monodispersity of the emulsion droplets allows us to measure the release profiles of a small molecular dye and a larger nanoparticle through the colloidosomes. It is further demonstrated that the preparation of monodisperse emulsions stabilized by other types of soft particles allows us control the stability of the emulsion with a pH trigger and improved biocompatibility. Thirdly, the preparation of multiple emulsions stabilized by a special designed PEG-b-PS diblock copolymer with desired hydrophobicity by one-step method was presented. The ultra-stability of the as-obtained multiple emulsions was ascribed to the effective steric stabilization of the two interfaces with different polymer configurations at the interfaces. A series of diblock copolymer with increasing PS chain length was then synthesized to investigate the influence of asymmetry ratio on the type of emulsions prepared. It is found that the diblock copolymers with the asymmetry ratio of approximately 1 had the highest power to stabilize multiple emulsions. The multiple emulsions were demonstrated to be a promising platform for controlled release. In the end, particle-stabilized water-in-air liquid marbles were investigated. PSco-MAA nanoparticles synthesized from surfactant-free emulsion polymerization were proved to be effective liquid marble stabilizers. The influence of drying conditions on the properties of liquid marbles was investigated through a macroscopic way. The pH value of the particle dispersion, which influences the protonation states of the particles before freeze-drying, has a profound influence on the property of the stabilized liquid marbles. A brief comment to the future of work of these investigated systems is delivered in the last part.

FAST TRACK COMMUNICATION: Gyration mode splitting in magnetostatically coupled magnetic vortices in an array

NASA Astrophysics Data System (ADS)

Barman, Anjan; Barman, Saswati; Kimura, T.; Fukuma, Y.; Otani, Y.

2010-10-01

We present the experimental observation of gyration mode splitting by the time-resolved magneto-optical Kerr effect in an array consisting of magnetostatically coupled Ni81Fe19 discs of 1 µm diameter, 50 nm thickness and inter-disc separations varying between 150 and 270 nm. A splitting of the vortex core gyration mode is observed when the inter-disc separation is 200 nm or less and the splitting is controllable by a bias magnetic field. The observed mode splitting is interpreted by micromagnetic simulations as the normal modes of the vortex cores analogous to the coupled classical oscillators. The splitting depends upon the strength of the inter-disc magnetostatic coupling mediated by magnetic side charges, which depends strongly on the magnetic ground states of the samples.

Experimental Study of Tip Vortex Flow from a Periodically Pitched Airfoil Section

NASA Technical Reports Server (NTRS)

Zaman, KBMQ; Fagan, A. F.; Mankbadi, M. R.

2016-01-01

An experimental investigation of a tip vortex from a NACA0012 airfoil is conducted in a low-speed wind tunnel at a chord Reynolds number of 4x10(exp 4). Initially, data for a stationary airfoil held at various angles-of-attack (alpha) are gathered. Detailed surveys are done for two cases: alpha=10 deg with attached flow and alpha=25 deg with massive flow separation on the upper surface. Distributions of various properties are obtained using hot-wire anemometry. Data include mean velocity, streamwise vorticity and turbulent stresses at various streamwise locations. For all cases, the vortex core is seen to involve a mean velocity deficit. The deficit apparently traces to the airfoil wake, part of which gets wrapped by the tip vortex. At small alpha, the vortex is laminar within the measurement domain. The strength of the vortex increases with increasing alpha but undergoes a sudden drop around alpha (is) greater than 16 deg. The drop in peak vorticity level is accompanied by transition and a sharp rise in turbulence within the core. Data are also acquired with the airfoil pitched sinusoidally. All oscillation cases pertain to a mean alpha=15 deg while the amplitude and frequency are varied. An example of phase-averaged data for an amplitude of +/-10 deg and a reduced frequency of k=0.2 is discussed. All results are compared with available data from the literature shedding further light on the complex dynamics of the tip vortex.

Filtered Rayleigh scattering mixing measurements of merging and non-merging streamwise vortex interactions in supersonic flow

NASA Astrophysics Data System (ADS)

Ground, Cody R.; Gopal, Vijay; Maddalena, Luca

2018-04-01

By introducing large-scale streamwise vortices into a supersonic flow it is possible to enhance the rate of mixing between two fluid streams. However, increased vorticity content alone does not explicitly serve as a predictor of mixing enhancement. Additional factors, particularly the mutual interactions occurring between neighboring vortical structures, affect the underlying fundamental physics that influence the rate at which the fluids mix. As part of a larger systematic study on supersonic streamwise vortex interactions, this work experimentally quantifies the average rate of mixing of helium and air in the presence of two separate modes of vortex interaction, the merging and non-merging of a pair of co-rotating vortices. In these experiments vortex-generating expansion ramps are placed on a strut injector. The freestream Mach number is set at 2.5 and helium is injected as a passive scalar. Average injectant mole fractions at selected flow planes downstream of the injector are measured utilizing the filtered Rayleigh scattering technique. The filtered Rayleigh scattering measurements reveal that, in the domain surveyed, the merging vortex interaction strongly displaces the plume from its initial horizontal orientation while the non-merging vortex interaction more rapidly mixes the helium and air. The results of the current experiments are consistent with associated knowledge derived from previous analyses of the two studied configurations which have included the detailed experimental characterization of entrainment, turbulent kinetic energy, and vorticity of both modes of vortex interaction.

Fluid-Structure Interactions as Flow Propagates Tangentially Over a Flexible Plate with Application to Voiced Speech Production

NASA Astrophysics Data System (ADS)

Westervelt, Andrea; Erath, Byron

2013-11-01

Voiced speech is produced by fluid-structure interactions that drive vocal fold motion. Viscous flow features influence the pressure in the gap between the vocal folds (i.e. glottis), thereby altering vocal fold dynamics and the sound that is produced. During the closing phases of the phonatory cycle, vortices form as a result of flow separation as air passes through the divergent glottis. It is hypothesized that the reduced pressure within a vortex core will alter the pressure distribution along the vocal fold surface, thereby aiding in vocal fold closure. The objective of this study is to determine the impact of intraglottal vortices on the fluid-structure interactions of voiced speech by investigating how the dynamics of a flexible plate are influenced by a vortex ring passing tangentially over it. A flexible plate, which models the medial vocal fold surface, is placed in a water-filled tank and positioned parallel to the exit of a vortex generator. The physical parameters of plate stiffness and vortex circulation are scaled with physiological values. As vortices propagate over the plate, particle image velocimetry measurements are captured to analyze the energy exchange between the fluid and flexible plate. The investigations are performed over a range of vortex formation numbers, and lateral displacements of the plate from the centerline of the vortex trajectory. Observations show plate oscillations with displacements directly correlated with the vortex core location.

Interaction of vortex rings with multiple permeable screens

NASA Astrophysics Data System (ADS)

Musta, Mustafa N.; Krueger, Paul S.

2014-11-01

Interaction of a vortex ring impinging on multiple permeable screens orthogonal to the ring axis was studied to experimentally investigate the persistence and decay of vortical structures inside the screen array using digital particle image velocimetry in a refractive index matched environment. The permeable screens had porosities (open area ratios) of 83.8%, 69.0%, and 55.7% and were held by a transparent frame that allowed the screen spacing to be changed. Vortex rings were generated using a piston-cylinder mechanism at nominal jet Reynolds numbers of 1000, 2000, and 3000 with piston stroke length-to-diameter ratios of 2 and 3. The interaction of vortex rings with the porous medium showed a strong dependence of the overall flow evolution on the screen porosity, with a central flow being preserved and vortex ring-like structures (with smaller diameter than the primary vortex ring) being generated near the centerline. Due to the large rod size used in the screens, immediate reformation of the transmitted vortex ring with size comparable to the primary ring (as has been observed with thin screens) was not observed in most cases. Since the screens have lower complexity and high open area ratios, centerline vortex ring-like flow structures formed with comparable size to the screen pore size and penetrated through the screens. In the case of low porosity screens (55.7%) with large screen spacing, re-emergence of large scale (large separation), weak vortical structures/pairs (analogous to a transmitted vortex ring) was observed downstream of the first screen. Additional smaller scale vortical structures were generated by the interaction of the vortex ring with subsequent screens. The size distribution of the generated vortical structures were shown to be strongly affected by porosity, with smaller vortical structures playing a stronger role as porosity decreased. Finally, porosity significantly affected the decay of total energy, but the effect of screen spacing decreased as porosity decreased.

Direct numerical simulation of steady state, three dimensional, laminar flow around a wall mounted cube

NASA Astrophysics Data System (ADS)

Liakos, Anastasios; Malamataris, Nikolaos A.

2014-05-01

The topology and evolution of flow around a surface mounted cubical object in three dimensional channel flow is examined for low to moderate Reynolds numbers. Direct numerical simulations were performed via a home made parallel finite element code. The computational domain has been designed according to actual laboratory experiment conditions. Analysis of the results is performed using the three dimensional theory of separation. Our findings indicate that a tornado-like vortex by the side of the cube is present for all Reynolds numbers for which flow was simulated. A horseshoe vortex upstream from the cube was formed at Reynolds number approximately 1266. Pressure distributions are shown along with three dimensional images of the tornado-like vortex and the horseshoe vortex at selected Reynolds numbers. Finally, and in accordance to previous work, our results indicate that the upper limit for the Reynolds number for which steady state results are physically realizable is roughly 2000.

Vortex dynamics in Patient-Specific Stenotic Tricuspid and Bicuspid Aortic Valves pre- and post- Trans-catheter Aortic Valve Replacement

NASA Astrophysics Data System (ADS)

Hatoum, Hoda; Dasi, Lakshmi Prasad

2017-11-01

Understanding blood flow related adverse complications such as leaflet thrombosis post-transcatheter aortic valve implantation (TAVI) requires a deeper understanding of how patient-specific anatomic and hemodynamic factors, and relative valve positioning dictate sinus vortex flow and stasis regions. High resolution time-resolved particle image velocimetry measurements were conducted in compliant and transparent 3D printed patient-specific models of stenotic bicuspid and tricuspid aortic valve roots from patients who underwent TAVI. Using Lagrangian particle tracking analysis of sinus vortex flows and probability distributions of residence time and blood damage indices we show that (a) patient specific modeling provides a more realistic assessment of TAVI flows, (b) TAVI deployment alters sinus flow patterns by significantly decreasing sinus velocity and vorticity, and (c) relative valve positioning can control critical vortex structures that may explain preferential leaflet thrombosis corresponding to separated flow recirculation, secondary to valve jet vectoring relative to the aorta axis. This work provides new methods and understanding of the spatio-temporal aortic sinus vortex dynamics in post TAVI pathology. This study was supported by the Ohio State University DHLRI Trifit Challenge award.

Flow regimes in a trapped vortex cell

NASA Astrophysics Data System (ADS)

Lasagna, D.; Iuso, G.

2016-03-01

This paper presents results of an experimental investigation on the flow in a trapped vortex cell, embedded into a flat plate, and interacting with a zero-pressure-gradient boundary layer. The objective of the work is to describe the flow features and elucidate some of the governing physical mechanisms, in the light of recent investigations on flow separation control using vortex cells. Hot-wire velocity measurements of the shear layer bounding the cell and of the boundary layers upstream and downstream are reported, together with spectral and correlation analyses of wall-pressure fluctuation measurements. Smoke flow visualisations provide qualitative insight into some relevant features of the internal flow, namely a large-scale flow unsteadiness and possible mechanisms driving the rotation of the vortex core. Results are presented for two very different regimes: a low-Reynolds-number case where the incoming boundary layer is laminar and its momentum thickness is small compared to the cell opening, and a moderately high-Reynolds-number case, where the incoming boundary layer is turbulent and the ratio between the momentum thickness and the opening length is significantly larger than in the first case. Implications of the present findings to flow control applications of trapped vortex cells are also discussed.

Numerical Investigation of an Oscillating Flat Plate Airfoil

NASA Astrophysics Data System (ADS)

Mohaghegh, Fazlolah; Janechek, Matthew; Buchholz, James; Udaykumar, Hs

2017-11-01

This research investigates the vortex dynamics of a plunging flat plate airfoil by analyzing the vorticity transport in 2D simulations. A horizontal airfoil is subject to a freestream flow at Re =10000. A prescribed vertical sinusoidal motion is applied to the airfoil. Smoothed Profile Method (SPM) models the fluid-structure interaction. SPM as a diffuse interface model considers a thickness for the interface and applies a smooth transition from solid to fluid. As the forces on the airfoil are highly affected by the interaction of the generated vortices from the surface, it is very important to find out whether a diffuse interface solver can model a flow dominated by vorticities. The results show that variation of lift coefficient with time agrees well with the experiment. Study of vortex evolution shows that similar to experiments, when the plate starts moving downward from top, the boundary layer is attached to the surface and the leading-edge vortex (LEV) is very small. By time, LEV grows and rolls up and a secondary vortex emerges. Meanwhile, the boundary layer starts to separate and finally LEV detaches from the surface. In overall, SPM as a diffuse interface model can predict the lift force and vortex pattern accurately.

A Candidate Wake Vortex Strength Definition for Application to the NASA Aircraft Vortex Spacing System (AVOSS)

NASA Technical Reports Server (NTRS)

Hinton, David A.; Tatnall, Chris R.

1997-01-01

A significant effort is underway at NASA Langley to develop a system to provide dynamical aircraft wake vortex spacing criteria to Air Traffic Control (ATC). The system under development, the Aircraft Vortex Spacing System (AVOSS), combines the inputs of multiple subsystems to provide separation matrices with sufficient stability for use by ATC and sufficient monitoring to ensure safety. The subsystems include a meteorological subsystem, a wake behavior prediction subsystem, a wake sensor subsystem, and system integration and ATC interfaces. The proposed AVOSS is capable of using two factors, singly or in combination, for reducing in-trail spacing. These factors are wake vortex motion out of a predefined approach corridor and wake decay below a strength that is acceptable for encounter. Although basic research into the wake phenomena has historically used wake total circulation as a strength parameter, there is a requirement for a more specific strength definition that may be applied across multiple disciplines and teams to produce a real-time, automated system. This paper presents some of the limitations of previous applications of circulation to aircraft wake observations and describes the results of a preliminary effort to bound a spacing system strength definition.

Flow-around modes for a rhomboid wing with a stall vortex in the shock layer

NASA Astrophysics Data System (ADS)

Zubin, M. A.; Maximov, F. A.; Ostapenko, N. A.

2017-12-01

The results of theoretical and experimental investigation of an asymmetrical hypersonic flow around a V-shaped wing with the opening angle larger than π on the modes with attached shockwaves on forward edges, when the stall flow is implemented on the leeward wing cantilever behind the kink point of the cross contour. In this case, a vortex of nonviscous nature is formed in which the velocities on the sphere exceeding the speed of sound and resulting in the occurrence of pressure shocks with an intensity sufficient for the separation of the turbulent boundary layer take place in the reverse flow according to the calculations within the framework of the ideal gas. It is experimentally established that a separation boundary layer can exist in the reverse flow, and its structure is subject to the laws inherent to the reverse flow in the separation region of the turbulent boundary layer arising in the supersonic conic flow under the action of a shockwave incident to the boundary layer.

Discrete-vortex simulation of pulsating flow on a turbulent leading-edge separation bubble

NASA Technical Reports Server (NTRS)

Sung, Hyung Jin; Rhim, Jae Wook; Kiya, Masaru

1992-01-01

Studies are made of the turbulent separation bubble in a two-dimensional semi-infinite blunt plate aligned to a uniform free stream with a pulsating component. The discrete-vortex method is applied to simulate this flow situation because this approach is effective for representing the unsteady motions of the turbulent shear layer and the effect of viscosity near the solid surface. The numerical simulation provides reasonable predictions when compared with the experimental results. A particular frequency with a minimum reattachment is related to the drag reduction. The most effective frequency is dependent on the amplified shedding frequency. The turbulent flow structure is scrutinized. This includes the time-mean and fluctuations of the velocity and the surface pressure, together with correlations between the fluctuating components. A comparison between the pulsating flow and the non-pulsating flow at the particular frequency of the minimum reattachment length of the separation bubble suggests that the large-scale vortical structure is associated with the shedding frequency and the flow instabilities.

Investigation of Positively Curved Blade in Compressor Cascade Based on Transition Model

NASA Astrophysics Data System (ADS)

Chen, Shaowen; Lan, Yunhe; Zhou, Zhihua; Wang, Songtao

2016-06-01

Experiment and numerical simulation of flow transition in a compressor cascade with positively curved blade is carried out in a low speed. In the experimental investigation, the outlet aerodynamic parameters are measured using a five-hole aerodynamic probe, and an ink-trace flow visualization is applied to the cascade surface. The effects of transition flow on the boundary layer development, three-dimensional flow separation and aerodynamic performance are studied. The feasibility of a commercial computational fluid dynamic code is validated and the numerical results show a good agreement with experimental data. The blade-positive curving intensifies the radial force from the endwalls to the mid-span near the suction surface, which leads to the smaller scope of the intermittent region, the lesser extents of turbulence intensity and the shorter radial height of the separation bubble near the endwalls, but has little influence on the flow near the mid-span. The large passage vortex is divided into two smaller shedding vortexes under the impact of the radial pressure gradient due to the positively curved blade. The new concentrated shedding vortex results in an increase in the turbulence intensity and secondary flow loss of the corresponding region.

The aerodynamic characteristics of vortex ingestion for the F/A-18 inlet duct

NASA Technical Reports Server (NTRS)

Anderson, Bernhard H.

1991-01-01

A Reduced Navier-Stokes (RNS) solution technique was successfully combined with the concept of partitioned geometry and mesh generation to form a very efficient 3D RNS code aimed at the analysis-design engineering environment. Partitioned geometry and mesh generation is a pre-processor to augment existing geometry and grid generation programs which allows the solver to (1) recluster an existing gridlife mesh lattice, and (2) perturb an existing gridfile definition to alter the cross-sectional shape and inlet duct centerline distribution without returning to the external geometry and grid generator. The present results provide a quantitative validation of the initial value space marching 3D RNS procedure and demonstrates accurate predictions of the engine face flow field, with a separation present in the inlet duct as well as when vortex generators are installed to supress flow separation. The present results also demonstrate the ability of the 3D RNS procedure to analyze the flow physics associated with vortex ingestion in general geometry ducts such as the F/A-18 inlet. At the conditions investigated, these interactions are basically inviscid like, i.e., the dominant aerodynamic characteristics have their origin in inviscid flow theory.

Boundary layer energization by means of optimized vortex generators

NASA Technical Reports Server (NTRS)

Barber, T. J.; Mounts, J. S.; Mccormick, D. C.

1993-01-01

A three-dimensional, multi-block, multi-zone, Euler analysis has been developed and applied to analyze the flow processes induced by a lateral array of low profile vortex generators (VG). These vortex generators have been shown to alleviate boundary layer separation through the generation of streamwise vorticity. The analysis has been applied to help develop improved VG configurations in an efficient manner. Special attention has been paid to determining the accuracy requirements of the solver for calculations in which vortical mechanisms are dominant. The analysis has been used to assess the effectiveness or boundary layer energization capacity of different VG's, including the effect of scale and shape variation. Finally, the analysis has been validated through comparisons with experimental data obtained in a large-scale low-speed wind tunnel.

Predicting aerodynamic characteristics of vortical flows on three-dimensional configurations using a surface-singularity panel method

NASA Technical Reports Server (NTRS)

Maskew, B.

1983-01-01

A general low-order surface-singularity panel method is used to predict the aerodynamic characteristics of a problem where a wing-tip vortex from one wing closely interacts with an aft mounted wing in a low Reynolds Number flow; i.e., 125,000. Nonlinear effects due to wake roll-up and the influence of the wings on the vortex path are included in the calculation by using a coupled iterative wake relaxation scheme. The interaction also affects the wing pressures and boundary layer characteristics: these effects are also considered using coupled integral boundary layer codes and preliminary calculations using free vortex sheet separation modelling are included. Calculated results are compared with water tunnel experimental data with generally remarkably good agreement.

Blade vortex interaction noise reduction techniques for a rotorcraft

NASA Technical Reports Server (NTRS)

Charles, Bruce D. (Inventor); Hassan, Ahmed A. (Inventor); Tadghighi, Hormoz (Inventor); JanakiRam, Ram D. (Inventor); Sankar, Lakshmi N. (Inventor)

1996-01-01

An active control device for reducing blade-vortex interactions (BVI) noise generated by a rotorcraft, such as a helicopter, comprises a trailing edge flap located near the tip of each of the rotorcraft's rotor blades. The flap may be actuated in any conventional way, and is scheduled to be actuated to a deflected position during rotation of the rotor blade through predetermined regions of the rotor azimuth, and is further scheduled to be actuated to a retracted position through the remaining regions of the rotor azimuth. Through the careful azimuth-dependent deployment and retraction of the flap over the rotor disk, blade tip vortices which are the primary source for BVI noise are (a) made weaker and (b) pushed farther away from the rotor disk (that is, larger blade-vortex separation distances are achieved).

Chladni solitons and the onset of the snaking instability for dark solitons in confined superfluids.

PubMed

Muñoz Mateo, A; Brand, J

2014-12-19

Complex solitary waves composed of intersecting vortex lines are predicted in a channeled superfluid. Their shapes in a cylindrical trap include a cross, spoke wheels, and Greek Φ, and trace the nodal lines of unstable vibration modes of a planar dark soliton in analogy to Chladni's figures of membrane vibrations. The stationary solitary waves extend a family of solutions that include the previously known solitonic vortex and vortex rings. Their bifurcation points from the dark soliton indicating the onset of new unstable modes of the snaking instability are predicted from scale separation for Bose-Einstein condensates (BECs) and superfluid Fermi gases across the BEC-BCS crossover, and confirmed by full numerical calculations. Chladni solitons could be observed in ultracold gas experiments by seeded decay of dark solitons.

Observation of acoustic valley vortex states and valley-chirality locked beam splitting

NASA Astrophysics Data System (ADS)

Ye, Liping; Qiu, Chunyin; Lu, Jiuyang; Wen, Xinhua; Shen, Yuanyuan; Ke, Manzhu; Zhang, Fan; Liu, Zhengyou

2017-05-01

We report an experimental observation of the classical version of valley polarized states in a two-dimensional hexagonal sonic crystal. The acoustic valley states, which carry specific linear momenta and orbital angular momenta, were selectively excited by external Gaussian beams and conveniently confirmed by the pressure distribution outside the crystal, according to the criterion of momentum conservation. The vortex nature of such intriguing bulk crystal states was directly characterized by scanning the phase profile inside the crystal. In addition, we observed a peculiar beam-splitting phenomenon, in which the separated beams are constructed by different valleys and locked to the opposite vortex chirality. The exceptional sound transport, encoded with valley-chirality locked information, may serve as the basis of designing conceptually interesting acoustic devices with unconventional functions.

Blade vortex interaction noise reduction techniques for a rotorcraft

NASA Technical Reports Server (NTRS)

Charles, Bruce D. (Inventor); JanakiRam, Ram D. (Inventor); Hassan, Ahmed A. (Inventor); Tadghighi, Hormoz (Inventor); Sankar, Lakshmi N. (Inventor)

1998-01-01

An active control device for reducing blade-vortex interactions (BVI) noise generated by a rotorcraft, such as a helicopter, comprises a trailing edge flap located near the tip of each of the rotorcraft's rotor blades. The flap may be actuated in any conventional way, and is scheduled to be actuated to a deflected position during rotation of the rotor blade through predetermined regions of the rotor azimuth, and is further scheduled to be actuated to a retracted position through the remaining regions of the rotor azimuth. Through the careful azimuth-dependent deployment and retraction of the flap over the rotor disk, blade tip vortices which are the primary source for BVI noise are (a) made weaker and (b) pushed farther away from the rotor disk (that is, larger blade-vortex separation distances are achieved).

Theory of the vortex matter transformations in high-Tc superconductor YBCO.

PubMed

Li, Dingping; Rosenstein, Baruch

2003-04-25

Flux line lattice in type II superconductors undergoes a transition into a "disordered" phase such as vortex liquid or vortex glass, due to thermal fluctuations and random quenched disorder. We quantitatively describe the competition between the thermal fluctuations and the disorder using the Ginzburg-Landau approach. The following T-H phase diagram of YBCO emerges. There are just two distinct thermodynamical phases, the homogeneous and the crystalline one, separated by a single first order transition line. The line, however, makes a wiggle near the experimentally claimed critical point at 12 T. The "critical point" is reinterpreted as a (noncritical) Kauzmann point in which the latent heat vanishes and the line is parallel to the T axis. The magnetization, the entropy, and the specific heat discontinuities at melting compare well with experiments.

Flow past a Flat Plate with a Vortex/sink Combination

NASA Technical Reports Server (NTRS)

Mourtos, N. J.

1984-01-01

An attempt was made to model the so called leading edge vortex which forms over the leading edge of delta wings at high angles of attack. A simplified model was considered, namely that of a two-dimensional, inviscid, incompressible steady flow around a flat plate at an angle of attack with a stationary vortex detached on top, as well as a sink to simulate the strong spanwise flow. The results appear to agree qualitatively with experiments. A comparison was also made between the lift and the drag of this model and the corresponding results for two classical solutions: (1) that of totally attached flow over the plate with the Kutta condition satisfied at the trailing edge only: and (2) the Helmholtz solution of totally separated flow over the plate.

Chladni Solitons and the Onset of the Snaking Instability for Dark Solitons in Confined Superfluids

NASA Astrophysics Data System (ADS)

Muñoz Mateo, A.; Brand, J.

2014-12-01

Complex solitary waves composed of intersecting vortex lines are predicted in a channeled superfluid. Their shapes in a cylindrical trap include a cross, spoke wheels, and Greek Φ , and trace the nodal lines of unstable vibration modes of a planar dark soliton in analogy to Chladni's figures of membrane vibrations. The stationary solitary waves extend a family of solutions that include the previously known solitonic vortex and vortex rings. Their bifurcation points from the dark soliton indicating the onset of new unstable modes of the snaking instability are predicted from scale separation for Bose-Einstein condensates (BECs) and superfluid Fermi gases across the BEC-BCS crossover, and confirmed by full numerical calculations. Chladni solitons could be observed in ultracold gas experiments by seeded decay of dark solitons.

Flow past a flat plat with a vortex/sink combination

NASA Technical Reports Server (NTRS)

Mourtos, N. J.

1985-01-01

An attempt was made to model the so called leading edge vortex which forms over the leading edge of delta wings at high angles of attack. A simplified model was considered, namely that of a two-dimensional, inviscid, incompressible steady flow around a flat plate at an angle of attack with a stationary vortex detached on top, as well as a sink to simulate the strong spanwise flow. The results appear to agree qualitatively with experiments. A comparison was also made between the lift and the drag of this model and the corresponding results for two classical solutions: (1) that of totally attached flow over the plate with the Kutta condition satisfied at the trailing edge only; and (2) the Helmholtz solution of totally separated flow over the plate.

A flexible, robust and antifouling asymmetric membrane based on ultra-long ceramic/polymeric fibers for high-efficiency separation of oil/water emulsions.

PubMed

Wang, Kui; Yiming, Wubulikasimu; Saththasivam, Jayaprakash; Liu, Zhaoyang

2017-07-06

Polymeric and ceramic asymmetric membranes have dominated commercial membranes for water treatment. However, polymeric membranes are prone to becoming fouled, while ceramic membranes are mechanically fragile. Here, we report a novel concept to develop asymmetric membranes based on ultra-long ceramic/polymeric fibers, with the combined merits of good mechanical stability, excellent fouling resistance and high oil/water selectivity, in order to meet the stringent requirements for practical oil/water separation. The ultra-long dimensions of ceramic nanofibers/polymeric microfibers endow this novel membrane with mechanical flexibility and robustness, due to the integrated and intertwined structure. This membrane is capable of separating oil/water emulsions with high oil-separation efficiency (99.9%), thanks to its nanoporous selective layer made of ceramic nanofibers. Further, this membrane also displays superior antifouling properties due to its underwater superoleophobicity and ultra-low oil adhesion of the ceramic-based selective layer. This membrane exhibits high water permeation flux (6.8 × 10 4 L m -2 h -1 bar -1 ) at low operation pressures, which is attributed to its 3-dimensional (3D) interconnected fiber-based structure throughout the membrane. In addition, the facile fabrication process and inexpensive materials required for this membrane suggest its significant potential for industrial applications.

Removal of oil droplets from water using carbonized rice husk: enhancement by surface modification using polyethylenimine.

PubMed

Lin, Kun-Yi Andrew; Yang, Hongta; Petit, Camille; Chen, Shen-Yi

2015-06-01

Carbonized rice husk (CRH) is a promising material to separate oil from water owing to its abundance, low-cost, and environmentally benign characteristics. However, CRH's performance is somewhat limited by its similar surface charge to that of oil, leading to repulsive interactions. To improve the separation efficiency of CRH, CRH was modified via impregnation with a cationic biocompatible polymer, polyethlyenimine (PEI) to form PEI-CRH. The modified sample exhibits a remarkably higher (10-50 times) oil/water (O/W) separation efficiency than that of the unmodified one. Small PEI-CRH particles (about 64 μm) are found to adsorb oil droplets faster and larger quantities than bigger particles (about 113 and 288 μm). PEI-CRH exhibits higher separation efficiency at high temperatures owing to the destabilization of the emulsion. It is also found that the oil adsorption mechanism involves a chemical interaction between PEI-CRH and oil droplets. The addition of NaCl considerably improves the separation efficiency, while the addition of a cationic surfactant has the opposite effect. In acidic emulsions, PEI-CRH adsorbs more oil than in neutral or basic conditions owing to favorable attractive forces between oil droplets and the surface of PEI-CRH. PEI-CRH can be easily regenerated by washing with ethanol. These promising features of PEI-CRH indicate that PEI-CRH could be an efficient and low-cost adsorbent for the O/W separation applications.

Rheology of interfacial protein-polysaccharide composites

NASA Astrophysics Data System (ADS)

Fischer, P.

2013-05-01

The morphology and mechanical properties of protein adsorption layers can significantly be altered by the presence of surfactants, lipids, particles, other proteins, and polysaccharides. In food emulsions, polysaccharides are primarily considered as bulk thickener but can under appropriate environmental conditions stabilize or destabilize the protein adsorption layer and, thus, the entire emulsion system. Despite their ubiquitous usage as stabilization agent, relatively few investigations focus on the interfacial rheology of composite protein/polysaccharide adsorption layers. The manuscript provides a brief review on both main stabilization mechanisms, thermodynamic phase separation and electrostatic interaction and discusses the rheological response in light of the environmental conditions such as ionic strength and pH.

Carbonate-coordinated metal complexes precede the formation of liquid amorphous mineral emulsions of divalent metal carbonates†

PubMed Central

Wolf, Stephan E.; Müller, Lars; Barrea, Raul; Kampf, Christopher J.; Leiterer, Jork; Panne, Ulrich; Hoffmann, Thorsten

2011-01-01

During the mineralisation of metal carbonates MCO3 (M = Ca, Sr, Ba, Mn, Cd, Pb) liquid-like amorphous intermediates emerge. These intermediates that form via a liquid/liquid phase separation behave like a classical emulsion and are stabilized electrostatically. The occurrence of these intermediates is attributed to the formation of highly hydrated networks whose stability is mainly based on weak interactions and the variability of the metal-containing pre-critical clusters. Their existence and compositional freedom are evidenced by electrospray ionization mass spectrometry (ESI-MS). Liquid intermediates in non-classical crystallisation pathways seem to be more common than assumed. PMID:21218241

Preliminary results of the on-demand vortex-generator experiments

NASA Technical Reports Server (NTRS)

Saddoughi, Seyed G.

1995-01-01

This is a report on the continuation of our experimental investigations (Saddoughi 1994) of 'on-demand' vortex generators. Conventional vortex generators as found on aircraft wings are mainly for suppression of separation during the off-design conditions. In cruise they perform no useful function and exert a significant drag penalty. Therefore, replacement of fixed rectangular or delta-wing generators by devices that could be activated when needed would be of interest. Also in our previous report, we described one example of an 'on-demand' device, which was developed by Jacobson & Reynolds (1995) at Stanford University, suitable for manufacture by micro-electro-mechanical technology. This device consists of a surface cavity elongated in the stream direction and covered with a lid cantilevered at the upstream end. The lid, which is a metal sheet with a sheet of piezoelectric ceramic bonded to it, lies flush with the boundary. On application of a voltage the ceramic expands or contracts; however, adequate amplitude can be obtained only by running at the cantilever resonance frequency and applying amplitude modulation: for 2.5 mm x 20 mm cantilevered lids, they obtained maximum tip displacements of the order of 100 pm. Thus fluid is expelled from the cavity through the gap around the lid on the downstroke. They used an asymmetrical gap configuration and found that periodic emerging jets on the narrow side induced periodic longitudinal vorticity into the boundary layer. Their device was used to modify the inner layer of the boundary layer for skin-friction reduction. The same method could be implemented for the replacement of the conventional vortex generators; however, to promote mixing and suppress separation we needed to deposit longitudinal vortices into the outer layer of the boundary layer, which required a larger vortex generator than the device built by Jacobson & Reynolds. Our vortex generator was built with a mechanically-driven cantilevered lid with an adjustable frequency. The device was made about ten times the size of Jacobson & Reynolds', the shape or size of the cavity and lid (28 mm x 250 mm) could be easily changed. The cavity depth, the cantilever-tip displacement, and the maximum lid frequency were 20 mm, 10 mm, and 60 Hz respectively. Our vortex generator was mounted on a turntable so that its yaw angle could be changed. Finally, tests over a range of ratios of vortex generator size to boundary-layer thickness could be carried out simply by changing the streamwise location of the device.

Texas A&M vortex type phase separator

NASA Astrophysics Data System (ADS)

Best, Frederick

2000-01-01

Phase separation is required for regenerative biological and chemical process systems as well as thermal transport and rejection systems. Liquid and gas management requirements for future spacecraft will demand small, passive systems able to operate over wide ranges of inlet qualities. Conservation and recycling of air and water is a necessary part of the construction and operation of the International Space Station as well as future long duration space missions. Space systems are sensitive to volume, mass, and power. Therefore, it is necessary to develop a method to recycle wastewater with minimal power consumption. Regenerative life support systems currently being investigated require phase separation to separate the liquid from the gas produced. The microgravity phase separator designed and fabricated at Texas A&M University relies on centripetal driven buoyancy forces to form a gas-liquid vortex within a fixed, right-circular cylinder. Two-phase flow is injected tangentially along the inner wall of this cylinder producing a radial acceleration gradient. The gradient produced from the intrinsic momentum of the injected mixture results in a rotating flow that drives the buoyancy process by the production of a hydrostatic pressure gradient. Texas A&M has flown several KC-135 flights with separator. These flights have included scaling studies, stability and transient investigations, and tests for inventory instrumentation. Among the hardware tested have been passive devices for separating mixed vapor/liquid streams into single-phase streams of vapor only and liquid only. .

Vortex dynamics of in-line twin synthetic jets in a laminar boundary layer

NASA Astrophysics Data System (ADS)

Wen, Xin; Tang, Hui; Duan, Fei

2015-08-01

An experimental investigation is conducted on the vortices induced by twin synthetic jets (SJs) in line with a laminar boundary layer flow over a flat plate. The twin SJs operating at four different phase differences, i.e., Δϕ = 0°, 90°, 180°, and 270°, are visualized using a stereoscopic color dye visualization system and measured using a two-dimensional particle image velocimetry (PIV) system. It is found that depending on the phase difference of twin SJs, three types of vortex structures are produced. At Δϕ = 90°, the two hairpin vortices interact in a very constructive way in terms of the vortex size, strength, and celerity, forming one combined vortex. At Δϕ = 270°, the two individual hairpin vortices do not have much interaction, forming two completely separated hairpin vortices that behave like doubling the frequency of the single SJ case. At Δϕ = 0° and 180°, the two hairpin vortices produced by the twin SJ actuators are close enough, with the head of one hairpin vortex coupled with the legs of the other, forming partially interacting vortex structures. Quantitative analysis of the twin SJs is conducted, including the time histories of vortex circulation in the mid-span plane as well as a selected spanwise-wall-normal plane, and the influence of the twin SJs on the boundary layer flow filed. In addition, dynamic mode decomposition analysis of the PIV data is conducted to extract representative coherent structures. Through this study, a better understanding in the vortex dynamics associated with the interaction of in-line twin SJs in laminar boundary layers is achieved, which provides useful information for future SJ-array applications.

Fluid mechanical dispersion of airborne pollutants inside urban street canyons subjecting to multi-component ventilation and unstable thermal stratifications.

PubMed

Mei, Shuo-Jun; Liu, Cheng-Wei; Liu, Di; Zhao, Fu-Yun; Wang, Han-Qing; Li, Xiao-Hong

2016-09-15

The pedestrian level pollutant transport in street canyons with multiple aspect ratios (H/W) is numerically investigated in the present work, regarding of various unstable thermal stratification scenarios and plain surrounding. Non-isothermal turbulent wind flow, temperature field and pollutant spread within and above the street canyons are solved by the realizable k-ε turbulence model along with the enhanced wall treatment. One-vortex flow regime is observed for shallow canyons with H/W=0.5, whereas multi-vortex flow regime is observed for deep canyons with H/W=2.0. Both one-vortex and multi-vortex regimes could be observed for the street canyons with H/W=1.0, where the secondary vortex could be initiated by the flow separation and intensified by unstable thermal stratification. Air exchange rate (AER) and pollutant retention time are adopted to respectively evaluate the street canyon ventilation and pollutant removal performance. A second-order polynomial functional relationship is established between AER and Richardson number (Ri). Similar functional relationship could be established between retention time and Ri, and it is only valid for canyons with one-vortex flow regime. In addition, retention time could be prolonged abruptly for canyons with multi-vortex flow regime. Very weak secondary vortex is presented at the ground level of deep canyons with mild stratification, where pollutants are highly accumulated. However, with the decrease of Ri, pollutant concentration adjacent to the ground reduces accordingly. Present research could be applied to guide the urban design and city planning for enhancing pedestrian environment. Copyright © 2016 Elsevier B.V. All rights reserved.

Generation of “perfect” vortex of variable size and its effect in angular spectrum of the down-converted photons

NASA Astrophysics Data System (ADS)

Jabir, M. V.; Apurv Chaitanya, N.; Aadhi, A.; Samanta, G. K.

2016-02-01

The “perfect” vortex is a new class of optical vortex beam having ring radius independent of its topological charge (order). One of the simplest techniques to generate such beams is the Fourier transformation of the Bessel-Gauss beams. The variation in ring radius of such vortices require Fourier lenses of different focal lengths and or complicated imaging setup. Here we report a novel experimental scheme to generate perfect vortex of any ring radius using a convex lens and an axicon. As a proof of principle, using a lens of focal length f = 200 mm, we have varied the radius of the vortex beam across 0.3-1.18 mm simply by adjusting the separation between the lens and axicon. This is also a simple scheme to measure the apex angle of an axicon with ease. Using such vortices we have studied non-collinear interaction of photons having orbital angular momentum (OAM) in spontaneous parametric down-conversion (SPDC) process and observed that the angular spectrum of the SPDC photons are independent of OAM of the pump photons rather depends on spatial profile of the pump beam. In the presence of spatial walk-off effect in nonlinear crystals, the SPDC photons have asymmetric angular spectrum with reducing asymmetry at increasing vortex radius.

Two improvements on numerical simulation of 2-DOF vortex-induced vibration with low mass ratio

NASA Astrophysics Data System (ADS)

Kang, Zhuang; Ni, Wen-chi; Zhang, Xu; Sun, Li-ping

2017-12-01

Till now, there have been lots of researches on numerical simulation of vortex-induced vibration. Acceptable results have been obtained for fixed cylinders with low Reynolds number. However, for responses of 2-DOF vortex-induced vibration with low mass ratio, the accuracy is not satisfactory, especially for the maximum amplitudes. In Jauvtis and Williamson's work, the maximum amplitude of the cylinder with low mass ratio m*=2.6 can reach as large as 1.5 D to be called as the "super-upper branch", but from current literatures, few simulation results can achieve such value, even fail to capture the upper branch. Besides, it is found that the amplitude decays too fast in the lower branch with the RANS-based turbulence model. The reason is likely to be the defects of the turbulence model itself in the prediction of unsteady separated flows as well as the unreasonable setting of the numerical simulation parameters. Aiming at above issues, a modified turbulence model is proposed in this paper, and the effect of the acceleration of flow field on the response of vortex-induced vibration is studied based on OpenFOAM. By analyzing the responses of amplitude, phase and trajectory, frequency and vortex mode, it is proved that the vortex-induced vibration can be predicted accurately with the modified turbulence model under appropriate flow field acceleration.

A Numerical Study of Anti-Vortex Film Cooling Designs at High Blowing Ratio

NASA Technical Reports Server (NTRS)

Heidmann, James D.

2008-01-01

A concept for mitigating the adverse effects of jet vorticity and liftoff at high blowing ratios for turbine film cooling flows has been developed and studied at NASA Glenn Research Center. This "anti-vortex" film cooling concept proposes the addition of two branched holes from each primary hole in order to produce a vorticity counter to the detrimental kidney vortices from the main jet. These vortices typically entrain hot freestream gas and are associated with jet separation from the turbine blade surface. The anti-vortex design is unique in that it requires only easily machinable round holes, unlike shaped film cooling holes and other advanced concepts. The anti-vortex film cooling hole concept has been modeled computationally for a single row of 30deg angled holes on a flat surface using the 3D Navier-Stokes solver Glenn-HT. A modification of the anti-vortex concept whereby the branched holes exit adjacent to the main hole has been studied computationally for blowing ratios of 1.0 and 2.0 and at density ratios of 1.0 and 2.0. This modified concept was selected because it has shown the most promise in recent experimental studies. The computational results show that the modified design improves the film cooling effectiveness relative to the round hole baseline and previous anti-vortex cases, in confirmation of the experimental studies.

Capacity and Wake Vortices

DOT National Transportation Integrated Search

2002-09-08

Aircraft wake vortices can pose a threat, especially in the terminal environment where aircraft operate in close proximity. Vortex separation standards preclude hazardous encounters, but are oftentimes very conservative. A key to increasing airport c...

Effect of demulsifiers on interfacial properties governing crude oil demulsification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukherjee, S.; Kushnick, A.P.

1988-05-01

Crude oil is almost always produced as persistent water-in-oil emulsions which must be resolved into two separate phases before the crude can be accepted for pipelining. The water droplets are sterically stabilized by the asphaltene and resin fractions of the crude oil. These are condensed aromatic rings containing saturated carbon chains and napthenic rings as substituents, along with a distribution of heteroatoms and metals. They are capable of crosslinking at the water drop-oil interface. Chemical demulsifiers are most commonly used to separate the emulsions into water and oil phases. The demulsifiers are moderate (2,000-50,000) molecular weight polydisperse mostly nonionic blockmore » copolymers with hydrophilic and hydrophobic segments. An example (Figure 1) of the most commonly used demulsifier is the oxyalkylated alkyl phenol formaldehyde resin. The alkyl group can be butyl, amyl, or nonyl and the interfacial activity is controlled by the relative amounts of ethylene oxide (EO) and propylene oxide (PO) attached to the polar end. The purpose of this paper is to illustrate how various parameters such as interfacial tension, interfacial shear viscosity, dynamic interfacial tension gradient, dilational elasticity and demulsifier clustering affect the demulsification effectiveness. To this end, the authors have studied both crude oil as well as asphaltene stabilized ''model' water-in-oil emulsions. In this paper, some of the results of the authors' study are presented.« less

PHYSICAL AND CHEMICAL STABILITY ANALYSIS OF COSMETIC MULTI- PLE EMULSIONS LOADED WITH ASCORBYL PALMITATE AND SODIUM ASCORBYL PHOSPHATE SALTS.

PubMed

Khan, Hira; Akhtar, Naveed; Ali, Atif; Khan, Haji M Shoaib; Sohail, Muhammad; Naeem, Muhammad; Nawaz, Zarqa

2016-09-01

Stability of hydrophilic and lipophilic vitamin C derivatives for quenching synergistic antioxidant activities and to treat oxidative related diseases is a major issue. This study was aimed to encapsulate hydrophilic and lipophilic vitamin C derivatives (ascorbyl palmitate and sodium ascorbyl phosphate) as functional ingredients in a newly formulated multiple emulsion of the W//W type to attain the synergistic antioxidant effects and the resultant system's long term physical and chemical stability. Several multiple emulsions using the same concentration of emulsifiers but different concentrations of ascorbyl palmitate and sodium ascorbyl phosphate were developed. Three finally selected multiple emulsions (ME₁, ME₂ and ME₃) were evaluated for physical stability in terms of rheology, microscopy, conductivity, pH, and organoleptic characteristics under different storage conditions for 3 months. Chemical stability was determined by HPLC on Sykam GmbH HPLC system (Germany), equipped with a variable UV detector. Results showed that at accelerated storage conditions all the three multiple emulsions had shear thinning behavior of varying shear stress with no influence of location of functional ingredients in a carrier system. Conductivity values increased and pH values remained within the skin pH range for 3 months. Microscopic analysis showed an increase in globule size with the passage of time, especially at higher temperatures while decreased at low temperatures. Centrifugation test did not cause phase separation till the 45th day, but little effects after 2 months. Chemical stability analysis by HPLC at the end of 3 months showed that ascorbyl palmitate and sodium ascorbyl phosphate were almost stable in all multiple emulsions with no influence of their location in a carrier system. Multiple emulsions were found a stable carrier for hydrophilic and lipophilic vitamin C derivatives to enhance their desired effects. Considering that many topical formulations contain simple vitamin C it is suggested that present study may contribute to the development of more stable formulations with a combination of vitamin C derivatives to enhance their cosmetic benefits.

A Method for Predicting Three-Degree-of-Freedom Store Separation Trajectories at Speeds up to the Critical Speed

DTIC Science & Technology

1971-07-01

the store ]ength. If the potential is constructed on this basis and the body pressure coefficients determined from the unsteady Bernoulli equation...term has a clear momentum interpretation. The second term isSfa biovant force as will now be shown. For irrotational plane flow, we have’ L ( 1- 1 7 ) n...p m p m 1!-4. EQUATIONS FOR VORTEX STRENGTHS In writing the equations for the vortex strengths, we start first v:i.t. ecuation (11-5) for the

An Initial Study of the Sensitivity of Aircraft Vortex Spacing System (AVOSS) Spacing Sensitivity to Weather and Configuration Input Parameters

NASA Technical Reports Server (NTRS)

Riddick, Stephen E.; Hinton, David A.

2000-01-01

A study has been performed on a computer code modeling an aircraft wake vortex spacing system during final approach. This code represents an initial engineering model of a system to calculate reduced approach separation criteria needed to increase airport productivity. This report evaluates model sensitivity toward various weather conditions (crosswind, crosswind variance, turbulent kinetic energy, and thermal gradient), code configurations (approach corridor option, and wake demise definition), and post-processing techniques (rounding of provided spacing values, and controller time variance).

Study of vortex generator influence on the flow in the wake of high-lift system wing

NASA Astrophysics Data System (ADS)

Bragin, N. N.; Ryabov, D. I.; Skomorokhov, S. I.; Slitinskaya, A. Yu.

2016-10-01

Passive vortex generators (VG) are known as one of the ways to improve the flow of the wings and other surfaces in the presence of flow separation. In particular, the VG are installed on the wings and nacelles of many foreign airplanes, including the most recent ones (for example, Boeing 787, Airbus A-350). The principle of the passive VG effects on flow is to transfer the kinetic energy of the external flow separation region by the vortices system arising from the flow VG themselves. For example, by increasing the angle of attack of the wing separation it is highly three-dimensional picture of the flow and sufficiently sensitive to external influences. Thus separated flow can be controlled when using the VG destroy large separation vortices. The VG effectiveness depends on many parameters. This is primarily the relative position of the second harmonic and the separation region on the wing and their size and position relative to each other, the orientation of the second harmonic relative to the local flow direction of the external flow, etc. Obviously, the VG effect will depend essentially on the intensity ratio of the second harmonic vortexes and nature of flow separation in the separation area. In the presence of intense flow separation the effect of conventional VG may be reduced or not occur at all. Until recently, investigations and selection of position of conventional VG were made only experimentally. Currently, the possibilities of calculation methods allow estimating the VG effect on the flow in the separation area. However, due to the phenomenon complexity the accuracy of these calculations is low. The experimental data are required to validate the computational methods, including information not only about the total impact, but also about the flow structure in the separation area. To obtain such information is the subject of this paper. In the test model of high-lift devices swept wing with modern supercritical profile the parametric studies were performed on the VG effects on the flow in the intensive separation zone on flaps. A number of VG types is considered that differ by configuration, size, location in relation to the area of flow separation on the flap, as well as the orientation relative to the incoming flow. The major part of standard of VG positions is investigated. The VG influence on head velocity loss and the characteristics of the amplitude-frequency spectra of pressure fluctuations in the wake of the wing are obtained, as well as the flow spectra are obtained by means of fluorescent mini-tufts.

Duality of circulation decay statistics and survival probability

DOT National Transportation Integrated Search

2010-09-01

Survival probability and circulation decay history have both been used for setting wake turbulence separation standards. Conceptually a strong correlation should exist between these two characterizations of the vortex behavior, however, the literatur...

Experimental investigation of starting characteristics and wave propagation from a shallow open cavity and its acoustic emission at supersonic speed

NASA Astrophysics Data System (ADS)

Pandian, S.; Desikan, S. L. N.; Niranjan, Sahoo

2018-01-01

Experiments were carried out on a shallow open cavity (L/D = 5) at a supersonic Mach number (M = 1.8) to understand its transient starting characteristics, wave propagation (inside and outside the cavity) during one vortex shedding cycle, and acoustic emission. Starting characteristics and wave propagation were visualized through time resolved schlieren images, while acoustic emissions were captured through unsteady pressure measurements. Results showed a complex shock system during the starting process which includes characteristics of the bifurcated shock system, shock train, flow separation, and shock wave boundary layer interaction. In one vortex shedding cycle, vortex convection from cavity leading edge to cavity trailing edge was observed. Flow features outside the cavity demonstrated the formation and downstream movement of a λ-shock due to the interaction of shock from the cavity leading edge and shock due to vortex and generation of waves on account of shear layer impingement at the cavity trailing edge. On the other hand, interesting wave structures and its propagation were monitored inside the cavity. In one vortex shedding cycle, two waves such as a reflected compression wave from a cavity leading edge in the previous vortex shedding cycle and a compression wave due to the reflection of Mach wave at the cavity trailing edge corner in the current vortex shedding cycle were visualized. The acoustic emission from the cavity indicated that the 2nd to 4th modes/tones are dominant, whereas the 1st mode contains broadband spectrum. In the present studies, the cavity feedback mechanism was demonstrated through a derived parameter coherence coefficient.

Improvement studies on emission and combustion characteristics of DICI engine fuelled with colloidal emulsion of diesel distillate of plastic oil, TiO2 nanoparticles and water.

PubMed

Karisathan Sundararajan, Narayanan; Ammal, Anand Ramachandran Bhagavathi

2018-04-01

Experimentation was conducted on a single cylinder CI engine using processed colloidal emulsions of TiO 2 nanoparticle-water-diesel distillate of crude plastic diesel oil as test fuel. The test fuel was prepared with plastic diesel oil as the principal constituent by a novel blending technique with an aim to improve the working characteristics. The results obtained by the test fuel from the experiments were compared with that of commercial petro-diesel (CPD) fuel for same engine operating parameters. Plastic oil produced from high density polyethylene plastic waste by pyrolysis was subjected to fractional distillation for separating plastic diesel oil (PDO) that contains diesel range hydrocarbons. The blending process showed a little improvement in the field of fuel oil-water-nanometal oxide colloidal emulsion preparation due to the influence of surfactant in electrostatic stabilization, dielectric potential, and pH of the colloidal medium on the absolute value of zeta potential, a measure of colloidal stability. The engine tests with nano-emulsions of PDO showed an increase in ignition delay (23.43%), and decrease in EGT (6.05%), BSNO x (7.13%), and BSCO (28.96%) relative to PDO at rated load. Combustion curve profiles, percentage distribution of compounds, and physical and chemical properties of test fuels ascertains these results. The combustion acceleration at diffused combustion phase was evidenced in TiO 2 emulsion fuels under study.

Liquid Fuel Emulsion Jet-in-Crossflow Penetration and Dispersion Under High Pressure Conditions

NASA Astrophysics Data System (ADS)

Gomez, Guillermo Andres

The current work focuses on the jet-in-crossflow penetration and dispersion behavior of water-in-oil emulsions in a high pressure environment. Both fuel injection strategies of using a water-in-oil emulsion and a jet-in-crossflow have demonstrated unique benefits in improving gas turbine performance from an emissions and efficiency standpoint. A jet-in-crossflow is very practical for use in gas turbine engines, rocket propulsion, and aircraft engines since it utilizes already available crossflow air to atomize fuel. Injecting water into a combustion chamber in the form of a water-in-oil emulsion allows for pollutant emissions reduction while reducing efficiency loses that may result from using a separate water or steam injection circuit. Dispersion effects on oil droplets are expected, therefore investigating the distribution of both oil and water droplets in the crossflow is an objective in this work. Understanding the synchronization and injection behavior of the two strategies is of key interest due to their combined benefits. A water-to-oil ratio and an ambient pressure parameter are developed for emulsion jet-in-crossflow trajectories. To this end, a total of 24 emulsion jet-in-crossflow tests were performed with varying ambient pressures of 2-8 atm and momentum flux ratios of 50, 85, and 120. Sobel edge filtering was applied to each averaged image obtained from a high speed video of each test case. Averaged and filtered images were used to resolve top and bottom edges of the trajectory in addition to the overall peak intensity up to 40 mm downstream of the injection point. An optimized correlation was established and found to differ from literature based correlations obtained under atmospheric pressure conditions. Overall it was found that additional parameters were not necessary for the top edge and peak intensity correlations, but a need for a unique emulsion bottom edge and width trajectory correlation was recognized. In addition to investigating emulsion jet-in-crossflow trajectory correlations, a unique Dual Planar Laser Induced Fluorescence (Dual-PLIF) method was applied for the first time on emulsions at elevated pressure conditions. From the Dual-PLIF results, qualitative observations provided insight into the unique dispersion of oil and water concentrations within a cross-sectional plane down stream of the jet-in-crossflow injection.

Perpendicular blade vortex interaction and its implications for helicopter noise prediction: Wave-number frequency spectra in a trailing vortex for BWI noise prediction

NASA Technical Reports Server (NTRS)

Devenport, William J.; Glegg, Stewart A. L.

1993-01-01

Perpendicular blade vortex interactions are a common occurrence in helicopter rotor flows. Under certain conditions they produce a substantial proportion of the acoustic noise. However, the mechanism of noise generation is not well understood. Specifically, turbulence associated with the trailing vortices shed from the blade tips appears insufficient to account for the noise generated. The hypothesis that the first perpendicular interaction experienced by a trailing vortex alters its turbulence structure in such a way as to increase the acoustic noise generated by subsequent interactions is examined. To investigate this hypothesis a two-part investigation was carried out. In the first part, experiments were performed to examine the behavior of a streamwise vortex as it passed over and downstream of a spanwise blade in incompressible flow. Blade vortex separations between +/- one eighth chord were studied for at a chord Reynolds number of 200,000. Three-component velocity and turbulence measurements were made in the flow from 4 chord lengths upstream to 15 chordlengths downstream of the blade using miniature 4-sensor hot wire probes. These measurements show that the interaction of the vortex with the blade and its wake causes the vortex core to loose circulation and diffuse much more rapidly than it otherwise would. Core radius increases and peak tangential velocity decreases with distance downstream of the blade. True turbulence levels within the core are much larger downstream than upstream of the blade. The net result is a much larger and more intense region of turbulent flow than that presented by the original vortex and thus, by implication, a greater potential for generating acoustic noise. In the second part, the turbulence measurements described above were used to derive the necessary inputs to a Blade Wake Interaction (BWI) noise prediction scheme. This resulted in significantly improved agreement between measurements and calculations of the BWI noise spectrum especially for the spectral peak at low frequencies, which previously was poorly predicted.

Engineering aspects of rate-related processes in food manufacturing.

PubMed

Adachi, Shuji

2015-01-01

Many rate-related phenomena occur in food manufacturing processes. This review addresses four of them, all of which are topics that the author has studied in order to design food manufacturing processes that are favorable from the standpoint of food engineering. They include chromatographic separation through continuous separation with a simulated moving adsorber, lipid oxidation kinetics in emulsions and microencapsulated systems, kinetic analysis and extraction in subcritical water, and water migration in pasta.

Continuous nanoparticle production by microfluidic-based emulsion, mixing and crystallization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su, Y.-F.; Kim, H.; Kovenklioglu, S.

2007-09-15

BaSO{sub 4} and 2,2'-dipyridylamine (DPA) nanoparticles were synthesized as reactive crystallization and anti-solvent recrystallization examples, respectively, of using the microfluidic-based emulsion and mixing approach as a new avenue of continuously producing inorganic and organic nanoparticles. BaSO{sub 4} nanoparticles in the size range of 15-100 nm were reactively precipitated within the confinement of an aqueous droplet which was coalesced from two separate aqueous droplets containing BaCl{sub 2} and (NH{sub 4}){sub 2}SO{sub 4} using a three T-junction micromixer configuration constructed with commercially available simple tubing and fitting supplies. Also, DPA nanoparticles of about 200 nm were crystallized by combining DPA+ethanol and watermore » droplets using the same micromixer configuration. - Graphical abstract: BaSO{sub 4} and 2,2'-dipyridylamine (DPA) nanoparticles were synthesized as reactive crystallization and anti-solvent recrystallization examples, respectively, of using the microfluidic-based emulsion and mixing approach as a new avenue of continuously producing inorganic and organic nanoparticles.« less

Evolution of volume fractions and droplet sizes by analysis of electrical conductance curves during destabilization of oil-in-water emulsions.

PubMed

Kostoglou, M; Varka, E-M; Kalogianni, E P; Karapantsios, T D

2010-09-01

Destabilization of hexane-in-water emulsions is studied by a continuous, non-intrusive, multi-probe, electrical conductance technique. Emulsions made of different oil fractions and surfactant (C(10)E(5)) concentrations are prepared in a stirred vessel using a Rushton turbine to break and agitate droplets. During the separation of phases, electrical signals from pairs of ring electrodes mounted at different heights onto the vessel wall, are recorded. The evolution of the local water volume fractions at the locations of the electrodes is estimated from these signals. It is found that in the absence of coalescence, the water fraction evolution curve from the bottom pair of electrodes is compatible with a bidisperse oil droplet size distribution. The sizes and volume fractions of the two droplet modes are estimated using theoretical arguments. The electrically determined droplet sizes are compared to data from microscopy image analysis. Results are discussed in detail. Copyright 2010 Elsevier Inc. All rights reserved.

Flight Test Analysis of the Forces and Moments Imparted on a B737-100 Airplane During Wake Vortex Encounters

NASA Technical Reports Server (NTRS)

Roberts, Chistopher L.

2001-01-01

Aircraft travel has become a major form of transportation. Several of our major airports are operating near their capacity limit, increasing congestion and delays for travelers. As a result, the National Aeronautics and Space Administration (NASA) has been working in conjunction with the Federal Aviation Administration (FAA), airline operators, and the airline industry to increase airport capacity without sacrificing public safety. One solution to the problem is to increase the number of airports and build new. runways; yet, this solution is becoming increasingly difficult due to limited space. A better solution is to increase the production per runway. This solution increases the possibility that one aircraft will encounter the trailing wake of another aircraft. Hazardous wake vortex encounters occur when an aircraft encounters the wake produced by a heavier aircraft. This heavy-load aircraft produces high-intensity wake turbulence that redistributes the aerodynamic loads of trailing smaller aircraft. This situation is particularly hazardous for smaller aircraft during takeoffs and landings. In order to gain a better understanding of the wake-vortex/aircraft encounter phenomena, NASA Langley Research Center conducted a series of flight tests from 1995 through 1997. These tests were designed to gather data for the development a wake encounter and wake-measurement data set with the accompanying atmospheric state information. This data set is being compiled into a database that can be used by wake vortex researchers to compare with experimental and computational results. The purpose of this research is to derive and implement a procedure for calculating the wake-vortex/aircraft interaction portion of that database by using the data recorded during those flight tests. There were three objectives to this research. Initially, the wake-induced forces and moments from each flight were analyzed based on varying flap deflection angles. The flap setting alternated between 15 and 30 degrees while the separation distance remained constant. This examination was performed to determine if increases in flap deflection would increase or decrease the effects of the wake-induced forces and moments. Next, the wake-induced forces and moments from each flight were analyzed based on separation distances of 1-3 nautical miles. In this comparison, flap deflection was held constant at 30 degrees. The purpose of this study was to determine if increased separation distances reduced the effects of the wake vortex on the aircraft. The last objective compared the wake-induced forces and moments of each flight as it executed a series of maneuvers through the wake-vortex. This analysis was conducted to examine the impact of the wake on the B737 as it traversed the wake horizontally and vertically. Results from the first analysis indicated that there was no difference in wake effect at flap deflections of 15 and 30 degrees. This conclusion is evidenced in the cases of the wake-induced sideforce, rolling moment, and yawing moment. The wake-induced lift, drag, and pitching moment cases yielded less conclusive results. The second analysis compared the wake-induced forces and moments at separation distances of 1-3 nautical miles. Results indicated that there was no significant difference in the wake-induced lift, drag, sideforce, or yawing moment coefficients. The analysis compared the wake-induced forces and moments based on different flight maneuvers. It was found that the wake-induced forces and moments had the greatest impact on out-to-in and in-to-out maneuvers.

Atmospheric Turbulence Effects on Near-Ground Wake Vortex Demise

DOT National Transportation Integrated Search

2008-01-20

The Federal Aviation Administration (FAA) and National Aeronautics and Space Administration (NASA) have been working jointly on a phased approach to implement wake avoidance solutions designed to safely reduce wake turbulence separation standards in ...

NASA AVOSS Fast-Time Wake Prediction Models: User's Guide

NASA Technical Reports Server (NTRS)

Ahmad, Nash'at N.; VanValkenburg, Randal L.; Pruis, Matthew

2014-01-01

The National Aeronautics and Space Administration (NASA) is developing and testing fast-time wake transport and decay models to safely enhance the capacity of the National Airspace System (NAS). The fast-time wake models are empirical algorithms used for real-time predictions of wake transport and decay based on aircraft parameters and ambient weather conditions. The aircraft dependent parameters include the initial vortex descent velocity and the vortex pair separation distance. The atmospheric initial conditions include vertical profiles of temperature or potential temperature, eddy dissipation rate, and crosswind. The current distribution includes the latest versions of the APA (3.4) and the TDP (2.1) models. This User's Guide provides detailed information on the model inputs, file formats, and the model output. An example of a model run and a brief description of the Memphis 1995 Wake Vortex Dataset is also provided.

On the Development of Turbulent Wakes from Vortex Streets

NASA Technical Reports Server (NTRS)

Roshko, Anatol

1954-01-01

Wake development behind circular cylinders at Reynolds numbers from 40 to 10,000 was investigated in a low-speed wind tunnel. Standard hot-wire techniques were used to study the velocity fluctuations. The Reynolds number range of periodic vortex shedding is divided into two distinct subranges. At r=40 to 150, called the stable range, regular vortex streets are formed and no turbulent velocity fluctuations accompany the periodic formation of vortices. The range r=150 to 300 is a transition range to a regime called the irregular range, in which turbulent velocity fluctuations accompany the periodic formation of vortices. The turbulence is initiated by laminar-turbulent transition in the free layers which spring from the separation points on the cylinder. The transition first occurs in the range r=150 to 300. Spectrum and statistical measurements were made to study the velocity fluctuations.

Vortex flow aerodynamics

NASA Technical Reports Server (NTRS)

Smith, J. H. B.; Campbell, J. F.; Young, A. D. (Editor)

1992-01-01

The principal emphasis of the meeting was to be on the understanding and prediction of separation-induced vortex flows and their effects on vehicle performance, stability, control, and structural design loads. This report shows that a substantial amount of the papers covering this area were received from a wide range of countries, together with an attendance that was even more diverse. In itself, this testifies to the current interest in the subject and to the appropriateness of the Panel's choice of topic and approach. An attempt is made to summarize each paper delivered, and to relate the contributions made in the papers and in the discussions to some of the important aspects of vortex flow aerodynamics. This reveals significant progress and important clarifications, but also brings out remaining weaknesses in predictive capability and gaps in understanding. Where possible, conclusions are drawn and areas of continuing concern are identified.

Anti-air pollution & energy conservation system for automobiles using leaded or unleaded gasoline, diesel or alternate fuel

DOEpatents

Bose, Ranendra K.

2002-06-04

Exhaust gases from an internal combustion engine operating with leaded or unleaded gasoline or diesel or natural gas, are used for energizing a high-speed gas turbine. The convoluting gas discharge causes a first separation stage by stratifying of heavier and lighter exhaust gas components that exit from the turbine in opposite directions, the heavier components having a second stratifying separation in a vortex tube to separate combustible pollutants from non-combustible components. The non-combustible components exit a vortex tube open end to atmosphere. The lighter combustible, pollutants effected in the first separation are bubbled through a sodium hydroxide solution for dissolving the nitric oxide, formaldehyde impurities in this gas stream before being piped to the engine air intake for re-combustion, thereby reducing the engine's exhaust pollution and improving its fuel economy. The combustible, heavier pollutants from the second separation stage are piped to air filter assemblies. This gas stream convoluting at a high-speed through the top stator-vanes of the air filters, centrifugally separates the coalescent water, aldehydes, nitrogen dioxides, sulfates, sulfur, lead particles which collect at the bottom of the bowl, wherein it is periodically released to the roadway. Whereas, the heavier hydrocarbon, carbon particles are piped through the air filter's porous element to the engine air intake for re-combustion, further reducing the engine's exhaust pollution and improving its fuel economy.

The fish tail motion forms an attached leading edge vortex

PubMed Central

Borazjani, Iman; Daghooghi, Mohsen

2013-01-01

The tail (caudal fin) is one of the most prominent characteristics of fishes, and the analysis of the flow pattern it creates is fundamental to understanding how its motion generates locomotor forces. A mechanism that is known to greatly enhance locomotor forces in insect and bird flight is the leading edge vortex (LEV) reattachment, i.e. a vortex (separation bubble) that stays attached at the leading edge of a wing. However, this mechanism has not been reported in fish-like swimming probably owing to the overemphasis on the trailing wake, and the fact that the flow does not separate along the body of undulating swimmers. We provide, to our knowledge, the first evidence of the vortex reattachment at the leading edge of the fish tail using three-dimensional high-resolution numerical simulations of self-propelled virtual swimmers with different tail shapes. We show that at Strouhal numbers (a measure of lateral velocity to the axial velocity) at which most fish swim in nature (approx. 0.25) an attached LEV is formed, whereas at a higher Strouhal number of approximately 0.6 the LEV does not reattach. We show that the evolution of the LEV drastically alters the pressure distribution on the tail and the force it generates. We also show that the tail's delta shape is not necessary for the LEV reattachment and fish-like kinematics is capable of stabilising the LEV. Our results suggest the need for a paradigm shift in fish-like swimming research to turn the focus from the trailing edge to the leading edge of the tail. PMID:23407826

Numerical study on wake characteristics of high-speed trains

NASA Astrophysics Data System (ADS)

Yao, Shuan-Bao; Sun, Zhen-Xu; Guo, Di-Long; Chen, Da-Wei; Yang, Guo-Wei

2013-12-01

Intensive turbulence exists in the wakes of high speed trains, and the aerodynamic performance of the trailing car could deteriorate rapidly due to complicated features of the vortices in the wake zone. As a result, the safety and amenity of high speed trains would face a great challenge. This paper considers mainly the mechanism of vortex formation and evolution in the train flow field. A real CRH2 model is studied, with a leading car, a middle car and a trailing car included. Different running speeds and cross wind conditions are considered, and the approaches of unsteady Reynold-averaged Navier-Stokes (URANS) and detached eddy simulation (DES) are utilized, respectively. Results reveal that DES has better capability of capturing small eddies compared to URANS. However, for large eddies, the effects of two approaches are almost the same. In conditions without cross winds, two large vortex streets stretch from the train nose and interact strongly with each other in the wake zone. With the reinforcement of the ground, a complicated wake vortex system generates and becomes strengthened as the running speed increases. However, the locations of flow separations on the train surface and the separation mechanism keep unchanged. In conditions with cross winds, three large vortices develop along the leeward side of the train, among which the weakest one has no obvious influence on the wake flow while the other two stretch to the tail of the train and combine with the helical vortices in the train wake. Thus, optimization of the aerodynamic performance of the trailing car should be aiming at reducing the intensity of the wake vortex system.

Transient interaction between a reaction control jet and a hypersonic crossflow

NASA Astrophysics Data System (ADS)

Miller, Warrick A.; Medwell, Paul R.; Doolan, Con J.; Kim, Minkwan

2018-04-01

This paper presents a numerical study that focuses on the transient interaction between a reaction control jet and a hypersonic crossflow with a laminar boundary layer. The aim is to better understand the underlying physical mechanisms affecting the resulting surface pressure and control force. Implicit large-eddy simulations were performed with a round, sonic, perfect air jet issuing normal to a Mach 5 crossflow over a flat plate with a laminar boundary layer, at a jet-to-crossflow momentum ratio of 5.3 and a pressure ratio of 251. The pressure distribution induced on the flat plate is unsteady and is influenced by vortex structures that form around the jet. A horseshoe vortex structure forms upstream and consists of six vortices: two quasi-steady vortices and two co-rotating vortex pairs that periodically coalesce. Shear-layer vortices shed periodically and cause localised high pressure regions that convect downstream with constant velocity. A longitudinal counter-rotating vortex pair is present downstream of the jet and is formed from a series of trailing vortices which rotate about a common axis. Shear-layer vortex shedding causes periodic deformation of barrel and bow shocks. This changes the location of boundary layer separation which also affects the normal force on the plate.

Highly Efficient Broadband Multiplexed Millimeter-Wave Vortices from Metasurface-Enabled Transmit-Arrays of Subwavelength Thickness

NASA Astrophysics Data System (ADS)

Jiang, Zhi Hao; Kang, Lei; Hong, Wei; Werner, Douglas H.

2018-06-01

Structured electromagnetic waves carrying nonvanishing orbital angular momentum (OAM) have recently opened up alternative frontiers in the field of wave physics, holding great promise for a wide range of potential applications. By leveraging geometric phases originating from spin-to-orbital interactions, spin-dependent wave phenomena can be created, leading to a more versatile realm of dispersionless wave-front manipulation. However, the currently available transmissive vortex-beam generators suffer from a narrow bandwidth, require an optically thick device profile, or are limited by a low efficiency, severely restricting their integration into systems and/or widespread usage for practical applications. We present the design methodology and a physical analysis and complete experimental characterization of a class of millimeter-wave Pancharatnam-Berry transmit-arrays with a thickness of about λ0/3 , which enables highly efficient generation and separation of spin-controlled vortex beams over a broad bandwidth, achieving an unprecedented peak efficiency of 88% for a single vortex beam and 71% for dual vortex beams. The proposed transmit-array, which is capable of providing two-dimensional OAM multiplexing and demultiplexing without normal-mode background interference, overcomes all previous roadblocks and paves the way for high-efficiency electromagnetic vortex-beam generation as well as other wave-front-shaping devices from microwave frequencies to optical wavelengths.

Unsteady behavior of leading-edge vortex and diffuser stall in a centrifugal compressor with vaned diffuser

NASA Astrophysics Data System (ADS)

Fujisawa, Nobumichi; Hara, Shotaro; Ohta, Yutaka

2016-02-01

The characteristics of a rotating stall of an impeller and diffuser and the evolution of a vortex generated at the diffuser leading-edge (i.e., the leading-edge vortex (LEV)) in a centrifugal compressor were investigated by experiments and numerical analysis. The results of the experiments revealed that both the impeller and diffuser rotating stalls occurred at 55 and 25 Hz during off-design flow operation. For both, stall cells existed only on the shroud side of the flow passages, which is very close to the source location of the LEV. According to the CFD results, the LEV is made up of multiple vortices. The LEV is a combination of a separated vortex near the leading- edge and a longitudinal vortex generated by the extended tip-leakage flow from the impeller. Therefore, the LEV is generated by the accumulation of vorticity caused by the velocity gradient of the impeller discharge flow. In partial-flow operation, the spanwise extent and the position of the LEV origin are temporarily transmuted. The LEV develops with a drop in the velocity in the diffuser passage and forms a significant blockage within the diffuser passage. Therefore, the LEV may be regarded as being one of the causes of a diffuser stall in a centrifugal compressor.

Stability of a Cosmetic Multiple Emulsion Loaded with Green Tea Extract

PubMed Central

Mahmood, Tariq; Akhtar, Naveed

2013-01-01

Multiple emulsions are excellent and exciting potential systems for the delivery of useful cosmetic agents. The work describes stability of a multiple emulsion for cosmetic purpose, loaded with extract of Camellia sinensis L. (Theaceae) in concentration of 5%. The formulation constitutes of cetyl dimethicone copolyol and polyoxyethylene (20) cetyl ether as emulsifiers and was characterised and monitored for various physicochemical aspects. Centrifugation has no devastating effect on physical destabilization/phase separation observed for 30 days. Mean globule sizes of multiple droplets were found in the range of 10.29 ± 4.4 μm to 12.77 ± 5.1 μm and of inner droplets were in the range of 0.8 ± 0.4 μm to 1.6 ± 0.8 μm. All samples exhibited shear thinning behavior with increase in shear stress. The results of the present study indicate that multiple emulsions can be used as carrier of 5% Camellia sinensis L. extract to enhance desired effects. The developed physically and chemically stable system is an effective system for targeting skin layers; however, long-term stability at elevated temperatures may be needed with suitable modifications, if required. PMID:24058284

Feasibility of Surfactant-Free Supported Emulsion Liquid Membrane Extraction

NASA Technical Reports Server (NTRS)

Hu, Shih-Yao B.; Li, Jin; Wiencek, John M.

2001-01-01

Supported emulsion liquid membrane (SELM) is an effective means to conduct liquid-liquid extraction. SELM extraction is particularly attractive for separation tasks in the microgravity environment where density difference between the solvent and the internal phase of the emulsion is inconsequential and a stable dispersion can be maintained without surfactant. In this research, dispersed two-phase flow in SELM extraction is modeled using the Lagrangian method. The results show that SELM extraction process in the microgravity environment can be simulated on earth by matching the density of the solvent and the stripping phase. Feasibility of surfactant-free SELM (SFSELM) extraction is assessed by studying the coalescence behavior of the internal phase in the absence of the surfactant. Although the contacting area between the solvent and the internal phase in SFSELM extraction is significantly less than the area provided by regular emulsion due to drop coalescence, it is comparable to the area provided by a typical hollow-fiber membrane. Thus, the stripping process is highly unlikely to become the rate-limiting step in SFSELM extraction. SFSELM remains an effective way to achieve simultaneous extraction and stripping and is able to eliminate the equilibrium limitation in the typical solvent extraction processes. The SFSELM design is similar to the supported liquid membrane design in some aspects.

FORMULATION AND STABILITY EVALUATION OF BAUHINIA VARIEGATA EXTRACT TOPICAL EMULSION.

PubMed

Mohsin, Sabeeh; Akhtar, Naveed

2017-05-01

This study presents the results for the development of water in oil (W/O) emulsion containing 2 % Bauhinia variegata (BV) extract with good antioxidant potential for cosmetic application. Different ratios of surfactant, oil and water were investigated to optimize the ratio of ingredients. It was found that emulsifier and oil4ratio were important in improving the stability of emulsion. The formulation having 2.5% Abil EM90, 12% liquid paraffin, 83.5% distilled water and 2% BV extract was found to be most stable. Stability of the formulation was further evaluated by characterizing for organoleptic, sedimentation, microscopic and rheological properties at a range of storage conditions for a period of 12 weeks. Experimental findings showed stable formulation behavior with respect to color change, liquefaction and phase separation. Centrifugation test was carried out to predict the long term stability..The rheological parameters were evaluated from Power Law and the flow index value less than 1 suggested non-Newtonian behavior of the W/O emulsion. The mean droplet size of the internal phase of freshly prepared formulation was 4.06 ? 1.99 pm that did not change significantly (p > 0.05) during the storage. The newly developed formulation exhibited promising attributes over long term storage and open opportunities for the topical delivery of natural antioxidants for cosmetic and pharmaceutical objectives.

Separation Of Liquid And Gas In Zero Gravity

NASA Technical Reports Server (NTRS)

Howard, Frank S.; Fraser, Wilson S.

1991-01-01

Pair of reports describe scheme for separating liquid from gas so liquid could be pumped. Designed to operate in absence of gravitation. Jet of liquid, gas, or liquid/gas mixture fed circumferentially into cylindrical tank filled with liquid/gas mixture. Jet starts liquid swirling. Swirling motion centrifugally separates liquid from gas. Liquid then pumped from tank at point approximately diametrically opposite point of injection of jet. Vortex phase separator replaces such devices as bladders and screens. Requires no components inside tank. Pumps for gas and liquid outside tank and easily accessible for maintenance and repairs.

Direct numerical simulation of steady state, three dimensional, laminar flow around a wall mounted cube

NASA Astrophysics Data System (ADS)

Liakos, Anastasios; Malamataris, Nikolaos

2014-11-01

The topology and evolution of flow around a surface mounted cubical object in three dimensional channel flow is examined for low to moderate Reynolds numbers. Direct numerical simulations were performed via a home made parallel finite element code. The computational domain has been designed according to actual laboratory experimental conditions. Analysis of the results is performed using the three dimensional theory of separation. Our findings indicate that a tornado-like vortex by the side of the cube is present for all Reynolds numbers for which flow was simulated. A horse-shoe vortex upstream from the cube was formed at Reynolds number approximately 1266. Pressure distributions are shown along with three dimensional images of the tornado-like vortex and the horseshoe vortex at selected Reynolds numbers. Finally, and in accordance to previous work, our results indicate that the upper limit for the Reynolds number for which steady state results are physically realizable is roughly 2000. Financial support of author NM from the Office of Naval Research Global (ONRG-VSP, N62909-13-1-V016) is acknowledged.

Application of Biot-Savart Solver to Predict Axis Switching Phenomena in Finite-Span Vortices Expelled from a Synthetic Jet

NASA Astrophysics Data System (ADS)

Straccia, Joseph; Farnsworth, John

2016-11-01

The Biot-Savart law is a simple yet powerful inviscid and incompressible relationship between the velocity induced at a point and the circulation, orientation and distance of separation of a vortex line. The authors have developed an algorithm for obtaining numerical solutions of the Biot-Savart relationship to predict the self-induced velocity on a vortex line of arbitrary shape. In this work the Biot-Savart solver was used to predict the self-induced propagation of non-circular, finite-span vortex rings expelled from synthetic jets with rectangular orifices of varying aspect ratios. The solver's prediction of the time varying shape of the vortex ring and frequency of axis switching was then compared with Particle Image Velocimetry (PIV) data from a synthetic jet expelled into a quiescent flow i.e. zero cross flow condition. Conclusions about the effectiveness and limitations of this simple, inviscid relationship are drawn from this experimental data. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE 1144083.

Numerical study of vortex rope during load rejection of a prototype pump-turbine

NASA Astrophysics Data System (ADS)

Liu, J. T.; Liu, S. H.; Sun, Y. K.; Wu, Y. L.; Wang, L. Q.

2012-11-01

A transient process of load rejection of a prototype pump-turbine was studied by three dimensional, unsteady simulations, as well as steady calculations.Dynamic mesh (DM) method and remeshing method were used to simulate the rotation of guide vanes and runner. The rotational speed of the runner was predicted by fluid couplingmethod. Both the transient calculation and steady calculation were performed based on turbulence model. Results show that steady calculation results have large error in the prediction of the external characteristics of the transient process. The runaway speed can reach 1.15 times the initial rotational speed during the transient process. The vortex rope occurs before the pump-turbine runs at zero moment point. Vortex rope has the same rotating direction with the runner. The vortex rope is separated into two parts as the flow rate decreases to 0. Pressure level decreases during the whole transient process.The transient simulation result were also compared and verified by experimental results. This computational method could be used in the fault diagnosis of transient operation, as well as the optimization of a transient process.

Orbit-induced localized spin angular momentum in strong focusing of optical vectorial vortex beams

NASA Astrophysics Data System (ADS)

Li, Manman; Cai, Yanan; Yan, Shaohui; Liang, Yansheng; Zhang, Peng; Yao, Baoli

2018-05-01

Light beams may carry optical spin or orbital angular momentum, or both. The spin and orbital parts manifest themselves by the ellipticity of the state of polarization and the vortex structure of phase of light beams, separately. Optical spin and orbit interaction, arising from the interaction between the polarization and the spatial structure of light beams, has attracted enormous interest recently. The optical spin-to-orbital angular momentum conversion under strong focusing is well known, while the converse process, orbital-to-spin conversion, has not been reported so far. In this paper, we predict in theory that the orbital angular momentum can induce a localized spin angular momentum in strong focusing of a spin-free azimuthal polarization vortex beam. This localized longitudinal spin of the focused field can drive the trapped particle to spin around its own axis. This investigation provides a new degree of freedom for spinning particles by using a vortex phase, which may have considerable potentials in optical spin and orbit interaction, light-beam shaping, or optical manipulation.

The impact of the eruptions of Mt. Pinatubo and Cerro Hudson on Antarctic aerosol levels during the 1991 Austral spring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pitts, M.C.; Thomason, L.W.

1993-11-19

At the beginning of 1991 Austral spring, volcanic aerosols from Mt. Pinatubo and Cerro Hudson were present in the polar stratosphere of the Southern Hemisphere. Satellite observations of aerosol extinction were used to identify and track the movement of these aerosols in the vicinity of the Antarctic vortex during August through November 1991. A layer of mature Mt. Pinatubo aerosols was identified near 21 km and a layer of fresh Cerro Hudson aerosols was identified near 12 km. This altitude separation of the Mt. Pinatubo and Cerro Hudson aerosols was observed throughout the period. Below 15 km, the polar stratospheremore » was subject to episodes of strong wave activity which transported the Cerro Hudson aerosols poleward and, after the middle of September, they became a persistent feature beneath the vortex. Above 15 km, signatures of Mt. Pinatubo aerosols were observed near the vortex boundary, but significant portions of the vortex interior remained free of any detectable intrusions of Mt. Pinatubo aerosols until the final warming in mid-November. 13 refs., 4 figs.« less

A biphasic oxidation of alcohols to aldehydes and ketones using a simplified packed-bed microreactor

PubMed Central

Bogdan, Andrew

2009-01-01

Summary We demonstrate the preparation and characterization of a simplified packed-bed microreactor using an immobilized TEMPO catalyst shown to oxidize primary and secondary alcohols via the biphasic Anelli-Montanari protocol. Oxidations occurred in high yields with great stability over time. We observed that plugs of aqueous oxidant and organic alcohol entered the reactor as plugs but merged into an emulsion on the packed-bed. The emulsion coalesced into larger plugs upon exiting the reactor, leaving the organic product separate from the aqueous by-products. Furthermore, the microreactor oxidized a wide range of alcohols and remained active in excess of 100 trials without showing any loss of catalytic activity. PMID:19478910

On the characteristics of emulsion chamber family events produced in low heights

NASA Technical Reports Server (NTRS)

Jing, G.; Jing, C.; Zhu, Q.; Ding, L.

1985-01-01

The uncertainty of the primary cosmic ray composition at 10 to the 14th power -10 to the 16th power eV is well known to make the study of the nuclear interaction mechanism more difficult. Experimentally considering, if one can identify effectively the family events which are produced in low heights, then an event sample induced by primary protons might be able to be separated. It is undoubtedly very meaningful. In this paper an attempt is made to simulate the family events under the condition of mountain emulsion chamber experiments with a reasonable model. The aim is to search for the dependence of some experimentally observable quantities to the interaction height.

Coarse-grained discrete particle simulations of particle segregation in rotating fluidized beds in vortex chambers [Discrete particle simulations of particle segregation in rotating fluidized beds in vortex chambers

DOE PAGES

Verma, Vikrant; Li, Tingwen; De Wilde, Juray

2017-05-26

Vortex chambers allow the generation of rotating fluidized beds, offering high-G intensified gas-solid contact, gas-solids separation and solids-solids segregation. Focusing on binary particle mixtures and fixing the density and diameter of the heavy/large particles, transient batch CFD-coarse-grained DPM simulations were carried out with varying densities or sizes of the light/small particles to evaluate to what extent combining these three functionalities is possible within a vortex chamber of given design. Both the rate and quality of segregation were analyzed. Within a relatively wide density and size range, fast and efficient segregation takes place, with an inner and slower rotating bed ofmore » the lighter/small particles forming within the outer and faster rotating bed of the heavier/large particles. Simulations show that the contamination of the outer bed with lighter particles occurs more easily than contamination of the inner bed with heavier particles and increases with decreasing difference in size or density of the particles. Bubbling in the inner bed is observed with an inner bed of very low density or small particles. Porosity plots show that vortex chambers with a sufficient number of gas inlet slots have to be used to guarantee a uniform gas distribution and particle bed. Lastly, the flexibility of particle segregation in vortex chambers with respect to the gas flow rate is demonstrated.« less

Modeling quantum fluid dynamics at nonzero temperatures

PubMed Central

Berloff, Natalia G.; Brachet, Marc; Proukakis, Nick P.

2014-01-01

The detailed understanding of the intricate dynamics of quantum fluids, in particular in the rapidly growing subfield of quantum turbulence which elucidates the evolution of a vortex tangle in a superfluid, requires an in-depth understanding of the role of finite temperature in such systems. The Landau two-fluid model is the most successful hydrodynamical theory of superfluid helium, but by the nature of the scale separations it cannot give an adequate description of the processes involving vortex dynamics and interactions. In our contribution we introduce a framework based on a nonlinear classical-field equation that is mathematically identical to the Landau model and provides a mechanism for severing and coalescence of vortex lines, so that the questions related to the behavior of quantized vortices can be addressed self-consistently. The correct equation of state as well as nonlocality of interactions that leads to the existence of the roton minimum can also be introduced in such description. We review and apply the ideas developed for finite-temperature description of weakly interacting Bose gases as possible extensions and numerical refinements of the proposed method. We apply this method to elucidate the behavior of the vortices during expansion and contraction following the change in applied pressure. We show that at low temperatures, during the contraction of the vortex core as the negative pressure grows back to positive values, the vortex line density grows through a mechanism of vortex multiplication. This mechanism is suppressed at high temperatures. PMID:24704874

Coarse-grained discrete particle simulations of particle segregation in rotating fluidized beds in vortex chambers [Discrete particle simulations of particle segregation in rotating fluidized beds in vortex chambers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verma, Vikrant; Li, Tingwen; De Wilde, Juray

Vortex chambers allow the generation of rotating fluidized beds, offering high-G intensified gas-solid contact, gas-solids separation and solids-solids segregation. Focusing on binary particle mixtures and fixing the density and diameter of the heavy/large particles, transient batch CFD-coarse-grained DPM simulations were carried out with varying densities or sizes of the light/small particles to evaluate to what extent combining these three functionalities is possible within a vortex chamber of given design. Both the rate and quality of segregation were analyzed. Within a relatively wide density and size range, fast and efficient segregation takes place, with an inner and slower rotating bed ofmore » the lighter/small particles forming within the outer and faster rotating bed of the heavier/large particles. Simulations show that the contamination of the outer bed with lighter particles occurs more easily than contamination of the inner bed with heavier particles and increases with decreasing difference in size or density of the particles. Bubbling in the inner bed is observed with an inner bed of very low density or small particles. Porosity plots show that vortex chambers with a sufficient number of gas inlet slots have to be used to guarantee a uniform gas distribution and particle bed. Lastly, the flexibility of particle segregation in vortex chambers with respect to the gas flow rate is demonstrated.« less

Under-oil superhydrophilic wetted PVDF electrospun modified membrane for continuous gravitational oil/water separation with outstanding flux.

PubMed

Obaid, M; Mohamed, Hend Omar; Yasin, Ahmed S; Yassin, Mohamed A; Fadali, Olfat A; Kim, HakYong; Barakat, Nasser A M

2017-10-15

Water in the world is becoming an increasingly scarce commodity and the membrane technology is a most effective strategy to address this issue. However, the fouling and low flux of the polymeric membrane remains the big challenges. Novel modified Polyvinylidene fluoride (PVDF) membrane was introduced, in this work, using a novel treatment technique for an electrospun polymeric PVDF membrane to be used in oil/water separation systems. The Characterizations of the modified and pristine membranes showed distinct changes in the phase and crystal structure of the membrane material as well as the wettability. The modification process altered the surface morphology and structure of the membrane by forming hydrophilic microspheres on the membrane surface. Therefore, the proposed treatment converts the membrane from highly hydrophobic to be a superhydrophilic under-oil when wetted with water. Accordingly, in the separation of oil/water mixtures, the modified membrane can achieve an outstanding flux of 20664 L/m 2 . hr under gravity, which is higher than the pristine membrane by infinite times. Moreover, in the separation of the emulsion, a high flux of 2727 L/m 2 . h was achieved. The results exhibited that the modified membrane can treat a huge amount of oily water with a minimal energy consumption. The corresponding separation efficiencies of both of oil/water mixtures and emulsion are more than 99%. The achieved characteristics for the modified and pristine membranes could be exploited to design a novel continuous system for oil/water separation with an excellent efficiency. Copyright © 2017 Elsevier Ltd. All rights reserved.

Experimental Study of Saddle Point of Attachment in Laminar Juncture Flow

NASA Technical Reports Server (NTRS)

Coon, Michael D.; Tobak, Murray

1995-01-01

An experimental study of laminar horseshoe vortex flows upstream of a cylinder/flat plate juncture has been conducted to verify the existence of saddle-point-of-attachment topologies. In the classical depiction of this flowfield, a saddle point of separation exists on the flat plate upstream of the cylinder, and the boundary layer separates from the surface. Recent computations have indicated that the topology may actually involve a saddle point of attachment on the surface and additional singular points in the flow. Laser light sheet flow visualizations have been performed on the symmetry plane and crossflow planes to identify the saddle-point-of-attachment flowfields. The visualizations reveal that saddle-point-of-attachment topologies occur over a range of Reynolds numbers in both single and multiple vortex regimes. An analysis of the flow topologies is presented that describes the existence and evolution of the singular points in the flowfield.

A new flow model for highly separated airfoil flows at low speeds

NASA Technical Reports Server (NTRS)

Zumwalt, G. W.; Naik, S. N.

1979-01-01

An analytical model for separated airfoil flows is presented which is based on experimentally observed physical phenomena. These include a free stagnation point aft of the airfoil and a standing vortex in the separated region. A computer program is described which iteratively matches the outer potential flow, the airfoil turbulent boundary layer, the separated jet entrainment, mass conservation in the separated bubble, and the rear stagnation pressure. Separation location and pressure are not specified a priori. Results are presented for surface pressure coefficient and compared with experiment for three angles of attack for a GA(W)-1, 17% thick airfoil.

Flowfield analysis of modern helicopter rotors in hover by Navier-Stokes method

NASA Technical Reports Server (NTRS)

Srinivasan, G. R.; Raghavan, V.; Duque, E. P. N.

1991-01-01

The viscous, three-dimensional, flowfields of UH60 and BERP rotors are calculated for lifting hover configurations using a Navier-Stokes computational fluid dynamics method with a view to understand the importance of planform effects on the airloads. In this method, the induced effects of the wake, including the interaction of tip vortices with successive blades, are captured as a part of the overall flowfield solution without prescribing any wake models. Numerical results in the form of surface pressures, hover performance parameters, surface skin friction and tip vortex patterns, and vortex wake trajectory are presented at two thrust conditions for UH60 and BERP rotors. Comparison of results for the UH60 model rotor show good agreement with experiments at moderate thrust conditions. Comparison of results with equivalent rectangular UH60 blade and BERP blade indicates that the BERP blade, with an unconventional planform, gives more thrust at the cost of more power and a reduced figure of merit. The high thrust conditions considered produce severe shock-induced flow separation for UH60 blade, while the BERP blade develops more thrust and minimal separation. The BERP blade produces a tighter tip vortex structure compared with the UH60 blade. These results and the discussion presented bring out the similarities and differences between the two rotors.

Experimental study of attached splitter plate effects on the wake of a circular cylinder using finite-time Lyapunov exponents

NASA Astrophysics Data System (ADS)

Brooks, Seth; Green, Melissa

2017-11-01

Two-component planar particle image velocimetry (PIV) and surface pressure were used to investigate the effects of an attached splitter plate on the formation and shedding of vortices from a circular cylinder. The instantaneous velocity data is phase averaged using the surface pressure. One of the tools used to visualize and characterize the flow is finite-time Lyapunov exponent (FTLE). This is a Lagrangian technique that identifies local separation. Prior literature shows that the addition of an attached splitter plate alters the classic von Kármán vortex shedding and that splitter plates longer than a certain length suppress the periodic shedding. A separate study proposes that the shedding of a vortex from a circular cylinder is characterized by a hyperbolic saddle leaving the vicinity of the surface and that the shedding time can be identified in real time using a surface pressure. In this study, the effects of splitter plates on the vortex shedding will be investigated where the plate will range in length from 1.5 D to 5.5 D , where D is the diameter of the cylinder. The FTLE and wake structure results will be compared with those found in previous studies that investigated the wake of bluff bodies with and without splitter plates.

The potential of hybrid micro-vortex generators to control flow separation of NACA 4415 airfoil in subsonic flow

NASA Astrophysics Data System (ADS)

Jumahadi, Muhammad Taufiq; Saad, Mohd Rashdan; Idris, Azam Che; Sujipto, Suriyadi; Rahman, Mohd Rosdzimin Abdul

2018-02-01

Boundary layer separation is detrimental to the lift and drag of most aeronautical applications. Many vortex generators (VG), both passive and active have been designed to reduce these drawbacks. This study targets to investigate the effectiveness of hybrid micro-VGs, which combine both active and passive micro-VGs in controlling separation under subsonic conditions. NACA 4415 airfoils installed with passive, active and hybrid micro-VGs each are designed, 3D printed, and tested in a wind tunnel at 26.19 m/s under Re = 2.5x105. The lift and drag measurements from a 3-component force balance prove that hybrid micro-VGs increase lift by up to 21.2%, increase drag by more than 11.3% and improve lift-to-drag ratio by at least 8.6% until up to 33.7%. From this research, it is believed that hybrid micro-VGs are competitive to the performance of active VGs and a better configuration is to be considered to reduce parasitic drag and outstand active VGs.

Comparison of Experimental Surface and Flow Field Measurements to Computational Results of the Juncture Flow Model

NASA Technical Reports Server (NTRS)

Roozeboom, Nettie H.; Lee, Henry C.; Simurda, Laura J.; Zilliac, Gregory G.; Pulliam, Thomas H.

2016-01-01

Wing-body juncture flow fields on commercial aircraft configurations are challenging to compute accurately. The NASA Advanced Air Vehicle Program's juncture flow committee is designing an experiment to provide data to improve Computational Fluid Dynamics (CFD) modeling in the juncture flow region. Preliminary design of the model was done using CFD, yet CFD tends to over-predict the separation in the juncture flow region. Risk reduction wind tunnel tests were requisitioned by the committee to obtain a better understanding of the flow characteristics of the designed models. NASA Ames Research Center's Fluid Mechanics Lab performed one of the risk reduction tests. The results of one case, accompanied by CFD simulations, are presented in this paper. Experimental results suggest the wall mounted wind tunnel model produces a thicker boundary layer on the fuselage than the CFD predictions, resulting in a larger wing horseshoe vortex suppressing the side of body separation in the juncture flow region. Compared to experimental results, CFD predicts a thinner boundary layer on the fuselage generates a weaker wing horseshoe vortex resulting in a larger side of body separation.

Vortex detection through pressure measurements

NASA Astrophysics Data System (ADS)

Bhide, Aditi

Vortex Generators (VGs) are known to hinder boundary layer separation, a frequently unwanted phenomenon when it comes to external flows over aircraft wings, on-ground vehicles or internal flows within pipes, diffusers and turbomachinery. Boundary layer separation leads to loss of lift, higher drag and subsequently, energy losses. The vortices generated inhibit boundary layer separation. This thesis is an effort to discern the strength and location of these generated vortices using an array of VGs over a flat plate. Such information may be useful in the future in active control systems for streamwise vortices, which have been proposed to relaminarize turbulent boundary layers. Flow over flat plates, simulated using wind tunnel experiments, is studied for pressure variation using an array of pressure ports mounted over the plate and connected to suitable pressure sensors. Pressure coefficient and Velocity maps are generated using the data obtained from the Kirsten Wind Tunnel data acquisition system. These represent the nature of the flow field over the plate and are used to locate the vortices and determine their strength. It was found that the vortices can be detected using this method and their strength and location can be estimated.

Magnetic Shocks and Substructures Excited by Torsional Alfvén Wave Interactions in Merging Expanding Flux Tubes

NASA Astrophysics Data System (ADS)

Snow, B.; Fedun, V.; Gent, F. A.; Verth, G.; Erdélyi, R.

2018-04-01

Vortex motions are frequently observed on the solar photosphere. These motions may play a key role in the transport of energy and momentum from the lower atmosphere into the upper solar atmosphere, contributing to coronal heating. The lower solar atmosphere also consists of complex networks of flux tubes that expand and merge throughout the chromosphere and upper atmosphere. We perform numerical simulations to investigate the behavior of vortex-driven waves propagating in a pair of such flux tubes in a non-force-free equilibrium with a realistically modeled solar atmosphere. The two flux tubes are independently perturbed at their footpoints by counter-rotating vortex motions. When the flux tubes merge, the vortex motions interact both linearly and nonlinearly. The linear interactions generate many small-scale transient magnetic substructures due to the magnetic stress imposed by the vortex motions. Thus, an initially monolithic tube is separated into a complex multithreaded tube due to the photospheric vortex motions. The wave interactions also drive a superposition that increases in amplitude until it exceeds the local Mach number and produces shocks that propagate upward with speeds of approximately 50 km s‑1. The shocks act as conduits transporting momentum and energy upward, and heating the local plasma by more than an order of magnitude, with a peak temperature of approximately 60,000 K. Therefore, we present a new mechanism for the generation of magnetic waveguides from the lower solar atmosphere to the solar corona. This wave guide appears as the result of interacting perturbations in neighboring flux tubes. Thus, the interactions of photospheric vortex motions is a potentially significant mechanism for energy transfer from the lower to upper solar atmosphere.

Animating Wall-Bounded Turbulent Smoke via Filament-Mesh Particle-Particle Method.

PubMed

Liao, Xiangyun; Si, Weixin; Yuan, Zhiyong; Sun, Hanqiu; Qin, Jing; Wang, Qiong; Heng, Pheng-Ann; Xiangyun Liao; Weixin Si; Zhiyong Yuan; Hanqiu Sun; Jing Qin; Qiong Wang; Pheng-Ann Heng

2018-03-01

Turbulent vortices in smoke flows are crucial for a visually interesting appearance. Unfortunately, it is challenging to efficiently simulate these appealing effects in the framework of vortex filament methods. The vortex filaments in grids scheme allows to efficiently generate turbulent smoke with macroscopic vortical structures, but suffers from the projection-related dissipation, and thus the small-scale vortical structures under grid resolution are hard to capture. In addition, this scheme cannot be applied in wall-bounded turbulent smoke simulation, which requires efficiently handling smoke-obstacle interaction and creating vorticity at the obstacle boundary. To tackle above issues, we propose an effective filament-mesh particle-particle (FMPP) method for fast wall-bounded turbulent smoke simulation with ample details. The Filament-Mesh component approximates the smooth long-range interactions by splatting vortex filaments on grid, solving the Poisson problem with a fast solver, and then interpolating back to smoke particles. The Particle-Particle component introduces smoothed particle hydrodynamics (SPH) turbulence model for particles in the same grid, where interactions between particles cannot be properly captured under grid resolution. Then, we sample the surface of obstacles with boundary particles, allowing the interaction between smoke and obstacle being treated as pressure forces in SPH. Besides, the vortex formation region is defined at the back of obstacles, providing smoke particles flowing by the separation particles with a vorticity force to simulate the subsequent vortex shedding phenomenon. The proposed approach can synthesize the lost small-scale vortical structures and also achieve the smoke-obstacle interaction with vortex shedding at obstacle boundaries in a lightweight manner. The experimental results demonstrate that our FMPP method can achieve more appealing visual effects than vortex filaments in grids scheme by efficiently simulating more vivid thin turbulent features.

Characteristics of Air Core and Surface Velocity for Water Flow in a Vortex Sediment-Extraction Chamber Measured by Using Photo Images and PTV Technique.

NASA Astrophysics Data System (ADS)

Yao, Hou Chang; Chyan Deng, Jan; Chao, Hsu Yu; Chih Yuan, Yang

2017-04-01

A vortex sediment-extraction chamber, consisted of cylindrical chamber, inflow system, bottom orifice and overflow weir, is used to separate sediment from sediment-laden water flow. A tangential inflow is introduced into a cylindrical chamber with a bottom orifice; thus, a strong vortex flow is produced there. Under actions of gravity and centrifugal force, heavier sediment particles are forced to move towards the bottom orifice, and relatively clear water flows over through the top overflow weir. The flow field in the cylindrical chamber consists of forced vortex and free vortex. When the bottom orifice is opened during the sediment-extraction process, an air core appears and changes with different settings. In this study, the air core and water surface velocity in the cylindrical chamber were measured by using a photo image process and particle tracking velocimetry (PTV), as well as numerically simulated by using a commercial software, Flow-3D.Laboratory experiments were conducted in a vortex chamber, having height of 130 cm and diameter of 48 cm. Five kinds of bottom orifice size from 1.0 cm to 3.0 cm and four kinds of inflow water discharge from 1,300cm3/s to 1,700 cm3/s were used while the inflow pipe of 3 cm in diameter was kept the same for all experiments. The characteristics of the air core and water surface velocity, and the inflow and outflow ratios under different experimental arrangements were observed and discussed so as to provide a better design and application for a vortex sediment-extraction chamber in the future.

Helical solutions of the bidirectional vortex in a cylindrical cyclone: Beltramian and Trkalian motions

NASA Astrophysics Data System (ADS)

Majdalani, Joseph

2012-10-01

In this work, two families of helical motions are investigated as prospective candidates for describing the bidirectional vortex field in a right-cylindrical chamber. These basic solutions are relevant to cyclone separators and to idealized representations of vortex-fired liquid and hybrid rocket engines in which bidirectional vortex motion is established. To begin, the bulk fluid motion is taken to be isentropic along streamlines, with no concern for reactions, heat transfer, viscosity, compressibility or unsteadiness. Then using the Bragg-Hawthorne equation for steady, inviscid, axisymmetric motion, two families of Euler solutions are derived. Among the characteristics of the newly developed solutions one may note the axial dependence of the swirl velocity, the Trkalian and Beltramian types of the helical motions, the sensitivity of the solutions to the outlet radius, the alternate locations of the mantle, and the increased axial and radial velocity magnitudes, including the rate of mass transfer across the mantle, for which explicit approximations are obtained. Our results are compared to an existing, complex lamellar model of the bidirectional vortex in which the swirl velocity reduces to a free vortex. In this vein, we find the strictly Beltramian flows to share virtually identical pressure variations and radial pressure gradients with those associated with the complex lamellar motion. Furthermore, both families warrant an asymptotic treatment to overcome their endpoint limitations caused by their omission of viscous stresses. From a broader perspective, the work delineates a logical framework through which self-similar, axisymmetric solutions to bidirectional and multidirectional vortex motions may be pursued. It also illustrates the manner through which different formulations may be arrived at depending on the types of wall boundary conditions. For example, both the slip condition at the sidewall and the inlet flow pattern at the headwall may be enforced or relaxed.

Theory, Computation and Experiment on Criticality and Stability of Vortices Separating from Edges

DTIC Science & Technology

2016-08-15

aerospace engineering research. These include dynamic stall in wind turbines and helicopter rotors, and flapping-wing vehicle (micro-air vehicle) design...and Robinson, M., “Blade Three-Dimensional Dynamic Stall Response to Wind Turbine Operating Condition,” Journal of Solar Energy Engineering , Vol...Snapshots of TEV shedding in vortex ring representation. . . . . . . . . . . . . . . . 57 7.3 Schematic description of separated tip flow model

Selective separation of lambdacyhalothrin by porous/magnetic molecularly imprinted polymers prepared by Pickering emulsion polymerization.

PubMed

Hang, Hui; Li, Chunxiang; Pan, Jianming; Li, Linzi; Dai, Jiangdong; Dai, Xiaohui; Yu, Ping; Feng, Yonghai

2013-10-01

Porous/magnetic molecularly imprinted polymers (PM-MIPs) were prepared by Pickering emulsion polymerization. The reaction was carried out in an oil/water emulsion using magnetic halloysite nanotubes as the stabilizer instead of a toxic surfactant. In the oil phase, the imprinting process was conducted by radical polymerization of functional and cross-linked monomers, and porogen chloroform generated steam under the high reaction temperature, which resulted in some pores decorated with easily accessible molecular binding sites within the as-made PM-MIPs. The characterization demonstrated that the PM-MIPs were porous and magnetic inorganic-polymer composite microparticles with magnetic sensitivity (M(s) = 0.7448 emu/g), thermal stability (below 473 K) and magnetic stability (over the pH range of 2.0-8.0). The PM-MIPs were used as a sorbent for the selective binding of lambdacyhalothrin (LC) and rapidly separated under an external magnetic field. The Freundlich isotherm model gave a good fit to the experimental data. The adsorption kinetics of the PM-MIPs was well described by pseudo-second-order kinetics, indicating that the chemical process could be the rate-limiting step in the adsorption of LC. The selective recognition experiments exhibited the outstanding selective adsorption effect of the PM-MIPs for target LC. Moreover, the PM-MIPs regeneration without significant loss in adsorption capacity was demonstrated by at least four repeated cycles. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation of gas selective membranes

DOEpatents

Kulprathipanja, Santi; Kulkarni, Sudhir S.; Funk, Edward W.

1988-01-01

Gas separation membranes which possess improved characteristics as exemplified by selectivity and flux may be prepared by coating a porous organic polymer support with a solution or emulsion of a plasticizer and an organic polymer, said coating being effected at subatmospheric pressures in order to increase the penetration depth of the coating material.

Preparation of gas selective membranes

DOEpatents

Kulprathipanja, S.; Kulkarni, S.S.; Funk, E.W.

1988-06-14

Gas separation membranes which possess improved characteristics as exemplified by selectivity and flux may be prepared by coating a porous organic polymer support with a solution or emulsion of a plasticizer and an organic polymer, said coating being effected at subatmospheric pressures in order to increase the penetration depth of the coating material.

Development of Recombinant Human Growth Hormone (rhGH) sustained-release microspheres by a low temperature aqueous phase/aqueous phase emulsion method.

PubMed

Kang, Jian; Wu, Fei; Cai, Yunpeng; Xu, Mingxin; He, Mu; Yuan, Weien

2014-10-01

A novel method has been developed to protect Recombinant Human Growth Hormone (rhGH) in poly (lactic-co-glycolic acid) (PLGA) microspheres using an aqueous phase/aqueous phase emulsion and S/O/W multi-emulsion method. This method develops a novel rhGH sustained-release system, which is based on the combination of rhGH-loaded dextran microparticles and PLGA microspheres. The process to fabricate rhGH-loaded dextran microparticles involves an aqueous phase/aqueous phase emulsion system formed at the reduced temperature. RhGH was first dissolved in water together with dextran and polyethylene glycol, followed by stirring at the speed of 2000 rpm for 20-30s at 0°C, and then a freezing process could enable the dextran phase to separate from the continuous PEG phase and rhGH could preferentially be loaded with dextran. The sample after freezing and phase separation was then lyophilized to powder and washed with dichloromethane to remove the PEG. Once loaded in the dextran microparticles (1-4 μm in diameter), rhGH gained resistance to interface tensions and was encapsulated into PLGA microspheres without aggregation thereafter. RhGH released from PLGA microspheres was in a sustained manner with minimal burst and maximally reduced incomplete release in vitro. Single subcutaneous injection of rhGH-loaded PLGA microspheres to rats resulted in a stable plasma concentration for 30 days avoiding the drug concentration fluctuations after multiple injections of protein solutions. In a hypophysectomized rat model, the IGF-1 and bodyweight results showed that there were higher than the levels obtained for the sustained release formulation by W/O/W for 40 days. These results suggest that the microsphere delivery system had the potential to be an injectable depot for sustained-release of the biocompatible protein of rhGH. Copyright © 2014 Elsevier B.V. All rights reserved.

SEPARATION AND CHARACTERIZATION OF HUMAN SERUM CHYLOMICRONS

PubMed Central

Scanu, Angelo; Page, Irvine H.

1959-01-01

Chylomicrons were separated by low and high speed ultracentrifugation from lipemic sera of human subjects in the absorptive phase. The final chylomicron preparation was free from other serum components and contained a small constant amount of protein, approximately 2 per cent of the chylomicron fraction. Electrophoresis, immunochemical analysis, and absorption experiments identified the protein component as derived from a mixture of beta and alpha1 serum lipoproteins. Large aliquots of an emulsion of serum freed of chylomicrons and coconut oil were incubated at 37°C. for 2 hours and ultracentrifuged as in the preparation of chylomicrons. The fat particles now showed the presence of minute amounts of beta and alpha1 serum lipoproteins in almost the same proportion as found in chylomicrons. "Finger prints" of delipidized samples of chylomicrons and particles from serum-coconut oil emulsion gave similar, although not identical patterns. The data on "clearing factor" activity corroborated the finding that serum alpha1 lipoproteins are contained in chylomicrons and particles from serum-coconut oil emulsion. These two lipide particles, partially delipidized, were both able to activate a "clearing factor" system in vitro, a property exhibited only by intact or partially delipidized alpha1 serum lipoproteins. Clearing activity was satisfactorily determined by using an emulsion of coconut oil mixed in agar as a substrate to give an opaque gel, in which the diffusing enzyme showed its activity by areas of clearing. The results obtained by this technique were in agreement with those based on fall in optical density and non-esterified fatty acid production. Chemical analysis of serum chylomicrons showed a concentration of cholesterol and phospholipides higher than could be accounted for by the attached beta and alpha1 serum lipoproteins. On the basis of these results the assumption is made that in the blood stream small amounts of serum lipoproteins, by a process of adsorption, form a complex with the absorbed triglycerides, cholesterol, and phospholipides, to produce chylomicrons. PMID:13620852

Crystallized and amorphous vortices in rotating atomic-molecular Bose-Einstein condensates

PubMed Central

Liu, Chao-Fei; Fan, Heng; Gou, Shih-Chuan; Liu, Wu-Ming

2014-01-01

Vortex is a topological defect with a quantized winding number of the phase in superfluids and superconductors. Here, we investigate the crystallized (triangular, square, honeycomb) and amorphous vortices in rotating atomic-molecular Bose-Einstein condensates (BECs) by using the damped projected Gross-Pitaevskii equation. The amorphous vortices are the result of the considerable deviation induced by the interaction of atomic-molecular vortices. By changing the atom-molecule interaction from attractive to repulsive, the configuration of vortices can change from an overlapped atomic-molecular vortices to carbon-dioxide-type ones, then to atomic vortices with interstitial molecular vortices, and finally into independent separated ones. The Raman detuning can tune the ratio of the atomic vortex to the molecular vortex. We provide a phase diagram of vortices in rotating atomic-molecular BECs as a function of Raman detuning and the strength of atom-molecule interaction. PMID:24573303

Helical vortices: linear stability analysis and nonlinear dynamics

NASA Astrophysics Data System (ADS)

Selçuk, C.; Delbende, I.; Rossi, M.

2018-02-01

We numerically investigate, within the context of helical symmetry, the dynamics of a regular array of two or three helical vortices with or without a straight central hub vortex. The Navier-Stokes equations are linearised to study the instabilities of such basic states. For vortices with low pitches, an unstable mode is extracted which corresponds to a displacement mode and growth rates are found to compare well with results valid for an infinite row of point vortices or an infinite alley of vortex rings. For larger pitches, the system is stable with respect to helically symmetric perturbations. In the nonlinear regime, we follow the time-evolution of the above basic states when initially perturbed by the dominant instability mode. For two vortices, sequences of overtaking events, leapfrogging and eventually merging are observed. The transition between such behaviours occurs at a critical ratio involving the core size and the vortex-separation distance. Cases with three helical vortices are also presented.

The W. M. Keck Observatory Infrared Vortex Coronagraph and a First Image of HIP 79124 B

NASA Astrophysics Data System (ADS)

Serabyn, E.; Huby, E.; Matthews, K.; Mawet, D.; Absil, O.; Femenia, B.; Wizinowich, P.; Karlsson, M.; Bottom, M.; Campbell, R.; Carlomagno, B.; Defrère, D.; Delacroix, C.; Forsberg, P.; Gomez Gonzalez, C.; Habraken, S.; Jolivet, A.; Liewer, K.; Lilley, S.; Piron, P.; Reggiani, M.; Surdej, J.; Tran, H.; Vargas Catalán, E.; Wertz, O.

2017-01-01

An optical vortex coronagraph has been implemented within the NIRC2 camera on the Keck II telescope and used to carry out on-sky tests and observations. The development of this new L‧-band observational mode is described, and an initial demonstration of the new capability is presented: a resolved image of the low-mass companion to HIP 79124, which had previously been detected by means of interferometry. With HIP 79124 B at a projected separation of 186.5 mas, both the small inner working angle of the vortex coronagraph and the related imaging improvements were crucial in imaging this close companion directly. Due to higher Strehl ratios and more relaxed contrasts in L‧ band versus H band, this new coronagraphic capability will enable high-contrast, small-angle observations of nearby young exoplanets and disks on a par with those of shorter-wavelength extreme adaptive optics coronagraphs.

Airfoil self-noise and prediction

NASA Technical Reports Server (NTRS)

Brooks, Thomas F.; Pope, D. Stuart; Marcolini, Michael A.

1989-01-01

A prediction method is developed for the self-generated noise of an airfoil blade encountering smooth flow. The prediction methods for the individual self-noise mechanisms are semiempirical and are based on previous theoretical studies and data obtained from tests of two- and three-dimensional airfoil blade sections. The self-noise mechanisms are due to specific boundary-layer phenomena, that is, the boundary-layer turbulence passing the trailing edge, separated-boundary-layer and stalled flow over an airfoil, vortex shedding due to laminar boundary layer instabilities, vortex shedding from blunt trailing edges, and the turbulent vortex flow existing near the tip of lifting blades. The predictions are compared successfully with published data from three self-noise studies of different airfoil shapes. An application of the prediction method is reported for a large scale-model helicopter rotor, and the predictions compared well with experimental broadband noise measurements. A computer code of the method is given.

Free-energy landscapes in magnetic systems from metadynamics

NASA Astrophysics Data System (ADS)

Tóbik, Jaroslav; MartoÅák, Roman; Cambel, Vladimír

2017-10-01

The knowledge of the free-energy barriers separating different states is critically important for the assessment of the long-term stability of information stored in magnetic devices. This information, however, is not directly accessible by standard simulations of microscopic models because of the ubiquitous time-scale problem, related to the fact that the transitions among different free-energy minima are characteristic of rare events. Here, we show that by employing the metadynamics algorithm based on suitably chosen collective variables, namely, helicity and circulation, it is possible to reliably recover the free-energy landscape. We demonstrate the effectiveness of this approach on an example of a vortex nucleation process in a magnetic nanodot with lowered spatial symmetry. With the help of reconstructed free-energy surfaces, we show the origin of symmetry broken vortex nucleation, where one polarity of the nucleated vortex core is preferred, even though only an in-plane magnetic field is present.

Dynamics of Perturbed Relative Equilibria of Point Vortices on the Sphere or Plane

NASA Astrophysics Data System (ADS)

Patrick, G. W.

2000-06-01

, and there are stable relative equilibria of four point vortices, where three identical point vortices form an equilateral triangle circling a central vortex. These relative equilibria have zero (nongeneric) momentum and form a family that extends to arbitrarily small diameters. Using the energy-momentum method, I show their shape is stable while their location on the sphere is unstable, and they move, after perturbation to nonzero momentum, on the sphere as point particles move under the influence of a magnetic monopole. In the analysis the internal and external degrees of freedom are separated and the mass of these point particles determined. In addition, two identical such relative equilibria attract one another, while opposites repel, and in energetic collisions, opposites disintegrate to vortex pairs while identicals interact by exchanging a vortex. An analogous situation also occurs for the planar system with its noncompact SE(2) symmetry.

Wake vortex capacity benefits for simultaneous approaches at St. Louis Airport

DOT National Transportation Integrated Search

1994-06-27

This paper details the results of FTA's investigation into the potential capacity gains of applying 1.5 nautical mile (NM) diagonal separation between parallel arrival operations at St. Louis Lambert International Airport (STL). Currently, dependent ...

A Conundrum of Tropical Cyclone Formation

NASA Astrophysics Data System (ADS)

Davis, C. A.

2014-12-01

This paper will address a conundrum that has emerged from recent research on tropical cyclone formation. Composite analyses and case studies suggest that prior to genesis, the atmosphere presents a mid-tropospheric vortex that is strong compared to the cyclonic circulation in the boundary layer. Accompanying this vortex is near saturation from the boundary layer through at least 5 km, sometimes more, and a nearly balanced weak negative temperature anomaly below the vortex and stronger positive temperature anomaly above. This thermodynamic state is one of high moisture but low buoyancy for lifted parcels (i.e. low convective available potential energy). However, observations also suggest that widespread deep convection accompanies genesis, with cloud top temperatures becoming colder near the time of genesis. This is seemingly at odds with in situ observations of thermodynamic characteristics prior to genesis. Progress toward understanding the apparent contradiction can be made by realizing that the existence of a moist, relatively stable vortex, and deep convective clouds are not necessarily coincident in space and time. This is demonstrated by a detailed analysis of the two days leading up to the formation of Atlantic tropical cyclone Karl on 14 September. Karl featured a relatively long gestation period characterized initially by a marked misalignment of mid-tropospheric and surface cyclonic circulations. The mid-tropospheric vortex strengthened due to a pulse of convection earlier on 13 September. Meanwhile, the near-surface vortex underwent a precession around the mid-tropospheric vortex as the separation between the two decreased. The eruption of convection around midnight on 14 September, 18 hours prior to declaration on a TC, occurred in the center of the nearly-aligned vortex, contained a mixture of shallow and deep convection and resulted in spin-up over a deep layer, but particularly at the surface. Prior to genesis, the most intense deep convection was located at least 200 km from the center.

Deflection and trapping of a counter-rotating vortex pair by a flat plate

NASA Astrophysics Data System (ADS)

Nitsche, Monika

2017-12-01

The interaction of a counter-rotating vortex pair (dipole) with a flat plate in its path is studied numerically. The vortices are initially separated by a distance D (dipole size) and placed far upstream of a plate of length L . The plate is centered on the dipole path and inclined relative to it at an incident angle βi. At first, the plate is held fixed in place. The vortices approach the plate, travel around it, and then leave as a dipole with unchanged velocity but generally a different travel direction, measured by a transmitted angle βt. For certain plate angles the transmitted angle is highly sensitive to changes in the incident angle. The sensitivity increases as the dipole size decreases relative to the plate length. In fact, for sufficiently small values of D /L , singularities appear: near critical values of βi, the dipole trajectory undergoes a topological discontinuity under changes of βi or D /L . The discontinuity is characterized by a jump in the winding number of one vortex around the plate, and in the time that the vortices take to leave the plate. The jumps occur repeatedly in a self-similar, fractal fashion, within a region near the critical values of βi, showing the existence of incident angles that trap the vortices, which never leave the plate. The number of these trapping regions increases as the parameter D /L decreases, and the dependence of the motion on βi becomes increasingly complex. The simulations thus show that even in this apparently simple scenario, the inviscid dynamics of a two-point-vortex system interacting with a stationary wall is surprisingly rich. The results are then applied to separate an incoming stream of dipoles by an oscillating plate.

Power reduction and the radial limit of stall delay in revolving wings of different aspect ratio

PubMed Central

Kruyt, Jan W.; van Heijst, GertJan F.; Altshuler, Douglas L.; Lentink, David

2015-01-01

Airplanes and helicopters use high aspect ratio wings to reduce the power required to fly, but must operate at low angle of attack to prevent flow separation and stall. Animals capable of slow sustained flight, such as hummingbirds, have low aspect ratio wings and flap their wings at high angle of attack without stalling. Instead, they generate an attached vortex along the leading edge of the wing that elevates lift. Previous studies have demonstrated that this vortex and high lift can be reproduced by revolving the animal wing at the same angle of attack. How do flapping and revolving animal wings delay stall and reduce power? It has been hypothesized that stall delay derives from having a short radial distance between the shoulder joint and wing tip, measured in chord lengths. This non-dimensional measure of wing length represents the relative magnitude of inertial forces versus rotational accelerations operating in the boundary layer of revolving and flapping wings. Here we show for a suite of aspect ratios, which represent both animal and aircraft wings, that the attachment of the leading edge vortex on a revolving wing is determined by wing aspect ratio, defined with respect to the centre of revolution. At high angle of attack, the vortex remains attached when the local radius is shorter than four chord lengths and separates outboard on higher aspect ratio wings. This radial stall limit explains why revolving high aspect ratio wings (of helicopters) require less power compared with low aspect ratio wings (of hummingbirds) at low angle of attack and vice versa at high angle of attack. PMID:25788539

Genesis of emulsion texture due to magma mixing: a case study from Chotanagpur Granite Gneiss Complex of Eastern India

NASA Astrophysics Data System (ADS)

Gogoi, Bibhuti; Saikia, Ashima; Ahmad, Mansoor

2016-04-01

The emulsion texture is a rare magma mixing feature in which rounded bodies of one magmatic phase remain dispersed in the other coherent phase (Freundt and Schmincke, 1992). This type of special texture in hybrid rocks can significantly contribute toward understanding the mechanisms facilitating magma mixing and magma chamber dynamics involving two disparate magmas as the exact processes by which mixing occurs still remain unclear. Recent developments in microfluidics have greatly helped us to understand the complex processes governing magma mixing occurring at micro-level. Presented work uses some of the results obtained from microfluidic experiments with a view to understand the formation mechanism of emulsions preserved in the hybrid rocks of the Ghansura Rhyolite Dome (GRD) of Proterozoic Chotanagpur Granite Gneiss Complex (CGGC), Eastern India. The GRD has preserved hybrid rocks displaying emulsion texture that formed due to the interaction of a phenocryst-rich basaltic magma and host rhyolite magma. The emulsions are more or less spherical in shape and dominantly composed of amphibole having biotite rinds set in a matrix of biotite, plagioclase, K-feldspar and quartz. Amphibole compositions were determined from the core of the emulsions to the rim with a view to check for cationic substitutions. The amphibole constituting the emulsions is actinolite in composition, and commonly shows tschermakite (Ts) and pargasite (Prg) substitutions. From petrographical and mineral-chemical analyses we infer that when mafic magma, containing phenocrysts of augite, came in contact with felsic magma, diffusion of cations like H+, Al3+and others occurred from the felsic to the mafic system. These cations reacted with the clinopyroxene phenocrysts in the mafic magma to form amphibole (actinolite) crystals. The formation of amphibole crystals in the mafic system greatly increased the viscosity of the system allowing the amphibole crystals to venture into the adjacent felsic magma as veins. As these veins traversed in the felsic medium they underwent sinuous perturbations as a result of the competition between the viscous torque, due to difference in drag on each side of the veins, and the dynamic viscous bending resistance (Cubaud and Mason, 2009). Further downstream, the undulations amplified and swirls started to develop on the sinuous veins by accumulating the high viscosity mafic phase into central bulbs and depleting the regions in between them forming tails. Gradually the tails thinned out and blended into the surrounding felsic melt forming discrete viscous emulsions/swirls. After separation, the amphibole constituting the emulsions started interacting with the surrounding felsic magma forming biotite at the periphery of the emulsions. Eventually, biotite is eroded away and new rinds simultaneously form on freshly eroded surfaces of emulsions facilitating the mixing process (Farner et al., 2014). Cubaud T and Mason TG (2009) New J. Phys. 11, 075029. Farner et al. (2014) Earth and Planetary Science Letters 393, 49-59. Freundt A and Schmincke HU (1992) Contrib Mineral Petrol 112, 1-19.

An analytical model for highly seperated flow on airfoils at low speeds

NASA Technical Reports Server (NTRS)

Zunnalt, G. W.; Naik, S. N.

1977-01-01

A computer program was developed to solve the low speed flow around airfoils with highly separated flow. A new flow model included all of the major physical features in the separated region. Flow visualization tests also were made which gave substantiation to the validity of the model. The computation involves the matching of the potential flow, boundary layer and flows in the separated regions. Head's entrainment theory was used for boundary layer calculations and Korst's jet mixing analysis was used in the separated regions. A free stagnation point aft of the airfoil and a standing vortex in the separated region were modelled and computed.

Semisolid formulations containing dimethyl sulfoxide and alpha-tocopherol for the treatment of extravasation of antiblastic agents.

PubMed

Casiraghi, Antonella; Ardovino, Paola; Minghetti, Paola; Botta, Cinzia; Gattini, Arrigo; Montanari, Luisa

2007-07-01

The topical treatment with dimethyl sulfoxide (DMSO) and/or alpha-tocopherol (alpha-T) is widely used in order to prevent the local complications of extravasation of cytostatic drugs and protect patients against skin ulceration. Till now, DMSO and alpha-T have been mainly used in solution. The goal of this study was to formulate semisolid preparations for cutaneous application differing in the hydrophilic and lipophilic properties and containing DMSO and alpha-T in combination. With respect to solutions, the use of semisolid preparations containing DMSO and alpha-T could be advantageous in patients having extravasation as DMSO and alpha-T can remain in contact with the skin over an extended period of time. As a consequence, the action of the active principles can be limited specifically on the injured skin area, reducing the cutaneous irritative effects of DMSO. The following types of semisolid formulations containing 50% m/m DMSO and 2.5% m/m alpha-T were prepared: hydrophilic ointment, o/w emulsion, hydrophilic gel and lipophilic gel. The ex vivo skin permeation of DMSO and alpha-T was evaluated by using modified Franz's diffusion cells and human stratum corneum and epidermis (SCE) as a membrane. The permeated and retained amounts of DMSO and alpha-T were determined. The oleogel preparation, the hydrophilic gel and the o/w emulsion were uniform in colour and aspect, without any evidences of phase separation over the period of the study. Hydrophilic ointments were discarded as they showed phase separation after 12 h. All formulations had a different behaviour in terms of skin permeability. In particular, hydrogel and o/w emulsion showed the best control on the drug release considering the interactions of the vehicle components with the SCE and the drugs partition between the vehicle and the SCE. The DMSO permeated amount after 24 h was 4.1 mg/cm(2) for hydrogel and 2.5 mg/cm(2) for emulsion while the permeated amount of pure DMSO after 24 h was 47.5 mg/cm(2). Therefore, aiming to reduce side effects after the topical application of the antidotes DMSO and alpha-T, these results suggested that hydrogel and o/w emulsion could be considered the most promising formulations for further clinical evaluations in managing of extravasation of anthracyclines.

Birth of a Loop Current Eddy

NASA Image and Video Library

2010-05-24

The northern portion of the Gulf of Mexico Loop Current, shown in red, appears about to detach a large ring of current, creating a separate eddy. An eddy is a large, warm, clockwise-spinning vortex of water -- the ocean version of a cyclone.

Active nematic emulsions

PubMed Central

Hardoüin, Jérôme; Sagués, Francesc

2018-01-01

The formation of emulsions from multiple immiscible fluids is governed by classical concepts such as surface tension, differential chemical affinity and viscosity, and the action of surface-active agents. Much less is known about emulsification when one of the components is active and thus inherently not constrained by the laws of thermodynamic equilibrium. We demonstrate one such realization consisting in the encapsulation of an active liquid crystal (LC)–like gel, based on microtubules and kinesin molecular motors, into a thermotropic LC. These active nematic emulsions exhibit a variety of dynamic behaviors that arise from the cross-talk between topological defects separately residing in the active and passive components. Using numerical simulations, we show a feedback mechanism by which active flows continuously drive the passive defects that, in response, resolve the otherwise degenerated trajectories of the active defects. Our experiments show that the choice of surfactant, which stabilizes the active/passive interface, allows tuning the regularity of the self-sustained dynamic events. The hybrid active-passive system demonstrated here provides new perspectives for dynamic self-assembly driven by an active material but regulated by the equilibrium properties of the passive component. PMID:29740605

Active nematic emulsions.

PubMed

Guillamat, Pau; Kos, Žiga; Hardoüin, Jérôme; Ignés-Mullol, Jordi; Ravnik, Miha; Sagués, Francesc

2018-04-01

The formation of emulsions from multiple immiscible fluids is governed by classical concepts such as surface tension, differential chemical affinity and viscosity, and the action of surface-active agents. Much less is known about emulsification when one of the components is active and thus inherently not constrained by the laws of thermodynamic equilibrium. We demonstrate one such realization consisting in the encapsulation of an active liquid crystal (LC)-like gel, based on microtubules and kinesin molecular motors, into a thermotropic LC. These active nematic emulsions exhibit a variety of dynamic behaviors that arise from the cross-talk between topological defects separately residing in the active and passive components. Using numerical simulations, we show a feedback mechanism by which active flows continuously drive the passive defects that, in response, resolve the otherwise degenerated trajectories of the active defects. Our experiments show that the choice of surfactant, which stabilizes the active/passive interface, allows tuning the regularity of the self-sustained dynamic events. The hybrid active-passive system demonstrated here provides new perspectives for dynamic self-assembly driven by an active material but regulated by the equilibrium properties of the passive component.

Intriguing Morphology Evolution from Noncrosslinked Poly(tert-butyl acrylate) Seeds with Polar Functional Groups in Soap-Free Emulsion Polymerization of Styrene.

PubMed

Wang, Lu; Pan, Mingwang; Song, Shaofeng; Zhu, Lei; Yuan, Jinfeng; Liu, Gang

2016-08-09

Herein, we demonstrate a facile approach to prepare anisotropic poly(tert-butyl acrylate)/polystyrene (PtBA/PS) composite particles with controllable morphologies by soap-free seeded emulsion polymerization (SSEP). In the first step, noncrosslinked PtBA seeds with self-stabilizing polar functional groups (e.g., ester groups and radicals) are synthesized by soap-free emulsion polymerization. During the subsequent SSEP of styrene (St), PS bulges are nucleated on the PtBA seeds due to the microphase separation confined in the latex particles. The morphology evolution of PtBA/PS composite particles is tailored by varying the monomer/seed feed ratio, polymerization time, and polymerization temperature. Many intriguing morphologies, including hamburger-like, litchi-like, mushroom-like, strawberry-like, bowl-like, and snowman-like, have been acquired for PtBA/PS composite particles. The polar groups on the PtBA seed surface greatly influence the formation and further merging of PS/St bulges during the polymerization. A possible formation mechanism is proposed on the basis of experimental results. These complex composite particles are promising for applications in superhydrophobic coatings.

Structurally Stable Attractive Nanoscale Emulsions with Dipole-Dipole Interaction-Driven Interdrop Percolation.

PubMed

Shin, Kyounghee; Gong, Gyeonghyeon; Cuadrado, Jonas; Jeon, Serim; Seo, Mintae; Choi, Hong Sung; Hwang, Jae Sung; Lee, Youngbok; Fernandez-Nieves, Alberto; Kim, Jin Woong

2017-03-28

This study introduces an extremely stable attractive nanoscale emulsion fluid, in which the amphiphilic block copolymer, poly(ethylene oxide)-block-poly(ϵ-caprolactone) (PEO-b-PCL), is tightly packed with lecithin, thereby forming a mechanically robust thin-film at the oil-water interface. The molecular association of PEO-b-PCL with lecithin is critical for formation of a tighter and denser molecular assembly at the interface, which is systematically confirmed by T 2 relaxation and DSC analyses. Moreover, suspension rheology studies also reflect the interdroplet attractions over a wide volume fraction range of the dispersed oil phase; this results in a percolated network of stable drops that exhibit no signs of coalescence or phase separation. This unique rheological behavior is attributed to the dipolar interaction between the phosphorylcholine groups of lecithin and the methoxy end groups of PEO-b-PCL. Finally, the nanoemulsion system significantly enhances transdermal delivery efficiency due to its favorable attraction to the skin, as well as high diffusivity of the nanoscale emulsion drops. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Massively parallel single-molecule and single-cell emulsion reverse transcription polymerase chain reaction using agarose droplet microfluidics.

PubMed

Zhang, Huifa; Jenkins, Gareth; Zou, Yuan; Zhu, Zhi; Yang, Chaoyong James

2012-04-17

A microfluidic device for performing single copy, emulsion Reverse Transcription Polymerase Chain Reaction (RT-PCR) within agarose droplets is presented. A two-aqueous-inlet emulsion droplet generator was designed and fabricated to produce highly uniform monodisperse picoliter agarose emulsion droplets with RT-PCR reagents in carrier oil. Template RNA or cells were delivered from one inlet with RT-PCR reagents/cell lysis buffer delivered separately from the other. Efficient RNA/cell encapsulation and RT-PCR at the single copy level was achieved in agarose-in-oil droplets, which, after amplification, can be solidified into agarose beads for further analysis. A simple and efficient method to graft primer to the polymer matrix using 5'-acrydite primer was developed to ensure highly efficient trapping of RT-PCR products in agarose. High-throughput single RNA molecule/cell RT-PCR was demonstrated in stochastically diluted solutions. Our results indicate that single-molecule RT-PCR can be efficiently carried out in agarose matrix. Single-cell RT-PCR was successfully performed which showed a clear difference in gene expression level of EpCAM, a cancer biomarker gene, at the single-cell level between different types of cancer cells. This work clearly demonstrates for the first time, single-copy RT-PCR in agarose droplets. We believe this will open up new possibilities for viral RNA detection and single-cell transcription analysis.

Physics of puffing and microexplosion of emulsion fuel droplets

NASA Astrophysics Data System (ADS)

Shinjo, J.; Xia, J.; Ganippa, L. C.; Megaritis, A.

2014-10-01

The physics of water-in-oil emulsion droplet microexplosion/puffing has been investigated using high-fidelity interface-capturing simulation. Varying the dispersed-phase (water) sub-droplet size/location and the initiation location of explosive boiling (bubble formation), the droplet breakup processes have been well revealed. The bubble growth leads to local and partial breakup of the parent oil droplet, i.e., puffing. The water sub-droplet size and location determine the after-puffing dynamics. The boiling surface of the water sub-droplet is unstable and evolves further. Finally, the sub-droplet is wrapped by boiled water vapor and detaches itself from the parent oil droplet. When the water sub-droplet is small, the detachment is quick, and the oil droplet breakup is limited. When it is large and initially located toward the parent droplet center, the droplet breakup is more extensive. For microexplosion triggered by the simultaneous growth of multiple separate bubbles, each explosion is local and independent initially, but their mutual interactions occur at a later stage. The degree of breakup can be larger due to interactions among multiple explosions. These findings suggest that controlling microexplosion/puffing is possible in a fuel spray, if the emulsion-fuel blend and the ambient flow conditions such as heating are properly designed. The current study also gives us an insight into modeling the puffing and microexplosion of emulsion droplets and sprays.