Ow Properties Research Articles

Rheology of paste-like food inks for 3D printing: Effects of nutrient and water content

This research delves into understanding the effects of composition on the rheological response of multi-component food inks for 3D food printing. Accordingly, the motivation is to decouple the nutrient and water content effects on the rheology. We formulated inks by combining pea fractions with water and employing a water-holding-capacity based hydration method. Rheology is characterized by steady shear rate and oscillatory strain amplitude sweeps. Strain sweep curves infer that the deformation response of all inks follows a similar trend, and samples sharing the same macronutrient formulation are mapped to a master curve after scaling with the elastic plateau modulus. Samples sharing the same macronutrient formulation mapped to a master curve after scaling with the elastic modulus. Shear rate testing showed that the inks were shear thinning yield stress materials. Shear rate sweeps also collapsed on a master curve scaled by the yield stress and critical shear rate on the y and x axes. The yield stress and the plateau modulus appeared to be controlled by the water content, while the shear and strain thinning exponents were independent of the formulations, inferring that the rheology is scaled by the water content while preserving the shear thinning response. Observing the independence of the rheological properties from the nutrient composition and scalability of the rheology by the water content provided a step forward in developing formulations with various nutrient content at desired ow properties, which promises personalized nutrition. Furthermore, the study shows the applicability of various rheological techniques, which are expected to contribute to the literature on the rheology of granular pastes.

The Use of Natural and Synthetic Polymers in the Formulation of Gastro retentive Drug Delivery System

The gastric emptying process drastically reduces the bioavailability of drugs that target the stomach for their action. A gastro retentive drug delivery system (GRDDS) becomes a solution to retain drugs in the stomach and release drugs from the formulation system within a certain period. The polymer used in the GRDDS formulation is the essential excipient that can retain the drugs in the stomach. Several ways for GRDDS to maintain its existence in the stomach are using some systems, such as mucoadhesive, low-density, high-density, swellable, eff ervescent, and expandable systems. A polymer is a macromolecular substance with a long repeating chain consisting of natural and synthetic polymers, each with diff erent potentials. It is considered for its ability to regulate drug release, good fl ow properties, can improve drug dissolution to improve bioavailability and stability during processing in the body. Combining natural and synthetic polymers is often carried out to obtain advantages and cover the existing polymer’s disadvantages. Polymers can release drugs using three diff erent mechanisms, i.e., diff usion, degradation, and expansion. These techniques are often chosen for the formulation of GRDDS because of their more fl exible system and fi t for almost all types of GRDDS. The polymer used in the GRDDS system is chosen from its physicochemical properties and the number of fl oating times, drug release rate, viscosity, fl oating lag times, bioavailability, and solubility.

THE CHARACTERISTICS OF A MIXTURE OF KEROSENE AND BIODIESEL AS A SUBSTITUTED DIESEL FUEL

Physicochemical properties characterization a mixture of biodiesel and kerosene were carried out toinvestigate their potential use as a substituted diesel fuel for domestic purposes. The characteristic assessmentswere done by comparing the standard requirement for diesel fuel. The properties characterization of thebiodiesel blends with kerosene were density, viscosity, pour point, cloud point, distillation, and cetane number,which is related to the cold fl ow properties of biodiesel. The characteristics fuel property of biodiesel blendswith kerosene in proportion at 2.5:97.5, 5:95, 10:90, 15:85, 20:80, 30:70, and 50:50 was found mostlymeet the requirement the specifi cation of diesel fuel. Biodiesel is mixed with kerosene to bring many of thebenefi cial characteristics to be a substituted diesel fuel. Overall physicochemical characteristics of blendingfuel were reduced by the increasing of kerosene concentrations. Kerosene can play a role as a diluent agentto reduce the characteristic of cold fl ow properties of biodiesel.

ARRESTING PROPAGATING SHEAR IN PIPELINES (Part 2. See no. 1, 2015 for part 1)

The consequences of what has been termed running ductile fracture require that pipelines be designed to arrest propagation, and so avoid major incidents due to this type of failure. Approaches to characterize pipeline response and their resistance to such failure to ensure arrest rely on semi-empirical models developed in the mid-1970s. Continuing reliance on such semi-empirical models, which were calibrated using fullscale tests done on segments of pipelines, persists because this failure process involves three interacting nonlinearities, and so is complex. These nonlinearities include: 1) plastic fl ow and tearing instability, 2) soil-structure interaction, and 3) expansion wave response and decompression in the pressurizing media. This paper fi rst reviews the history and related evelopments that represent almost 40 years invested in fracture-based approaches to quantify propagating shear in pipelines. Graphical evidence of the full-scale failure process and related phenomenology lead to an alternative hypothesis to quantify this failure process that is based on plastic collapse rather than fracture. It is shown that the phenomenology does not support a fracture-controlled process, and that instead the metrics of arrest should refl ect the fl ow properties of the steel. Finally, aspects of fracture-based approaches are related to the collapse-based concept as the basis to understand the success that at times has been achieved using fracture-based approaches. Surrogates for CVN energy that has been used in the BTCM as a measure of fracture resistance are reevaluated as functions of the fl ow response, which provides the basis to rationalize the historic successes on the fracture-based formulation. Finally, remaining gaps and issues are addressed.

Development of co-processed excipients in the design and evaluation of atorvastatin calcium tablets by direct compression method.

Introduction:Co-processed excipients were prepared to improve the process ability and efficacy of commonly used excipients and to impart multi-functional qualities to the excipients and hence that the tablets with the desired attributes can be produced. In this study, acacia and calcium carbonate (CaCO3) were used to prepare a co-processing excipient suitable for the preparation of atorvastatin calcium tablets. Acacia is used as binder and CaCO3 as filler. CaCO3 also acts as alkalizer and thus suitable to improve the dissolution rate of pH dependent soluble drugs like atorvastatin.Materials and Methods:The tablets were prepared by direct compression method and the physical properties of tablets such as hardness, friability and dissolution profiles of tablets were evaluated. Acacia was used in the form of mucilage. Various ratios of the co-processing excipients were formulated by granulation technique and the blend properties were evaluated by their Hausner's ratio and Carr's index values. Based on the Kawakita plots, it was found that the formulation with 3% acacia mucilage (0.9 mg acacia and 26.6 mg of CaCO3) showed good fluidity and the formulations with 4% (1.27 mg of acacia and 26.23 mg of CaCO3) and 5% acacia mucilage (1.62 mg of acacia and 25.88 mg of CaCO3) showed more cohesiveness. The formulations include 1-5% of the acacia mucilage as the binding agent.Results:The granules of formulations with low percentage of acacia mucilage (1% and 2%) failed the test for friability. The granules of the formulations with pure acacia (F1) and pure CaCO3 (F2) showed passable flow properties.Conclusion:The formulation with 3% acacia mucilage (F3, 0.9 mg acacia and 26.6 mg of CaCO3) showed least dissolution time (<1 min) and is found as the best formulation among the other formulations containing 4% (F4, 1.27 mg of acacia and 26.23 mg of CaCO3) and 5% (F5, 1.62 mg of acacia and 25.88 mg of CaCO3) acacia mucilage.

Fibrillar material as a cobinder in coating colors formulations

The micro-fibrillated cellulose (MFC) is a potential material which will at least partly substitute the synthetic co- binders, such as carboxymethyl cellulose (CMC), in paper coating color formulations. Co-binders play an important role in controlling both the flow properties and the dewatering rate of coating colors during the application process as well as during the subsequent film immobilization [25, 19, 02]. In this study, MFC fibers are used to substitute standard, synthetic co-binder material, CMC, affecting both dewatering and rheological properties of coating colors. This study was partly attempting to establish standard measurement procedures that can give overall picture of complex rheological behavior of MFC coating colors. Elastic effects of coating color in low shear rate influence both the flow and blade load [23]. By influencing leveling, elasticity, substitution of CMC with MFC influences coating color application and immobilization process, as well as the uniformity and optical properties of the coating film [06] . It has been demonstrated that coating colors which contained MFC fibers as a co-binder had pronounced shear-thinning characteristics which is a desirable property for paper coatings. However, a complete substitution of CMC with MFC fibers in paper coatings induced low retention properties, longer shear recovery time and fast immobilization of coating colors, which can have a negative influence on leveling and final coating layer uniformity. Coating suspension rheology of the coating influences the coating performance at high speeds. The quality of the coated and printed papers is also affected by the rheology of the suspension [06,26]. Co-binders play an important role in controlling both the flow properties and the dewatering rate of coating colors during the application process as well as during the subsequent film immobilization [23,06]. The micro fibrillated cellulose (MFC) is a potential material which will at least partly substitute the synthetic co-binders, such as carboxymethyl cellulose (CMC), in paper coating color formulations [08,22]. It was expected that the introduction of the MFC material into the coating formulation affects the coating color rheology since the MFC fibers are highly flocculated and have reactive groups on their surface [08].Micro-fibrillated cellulose material (MFC), can be produced through several pre-treatment and refining routes, each giving products with very different morphological and chemical properties [18].It is expected that refining and treatment route of MFC influence traditional coating layer properties as those designed for special purposes [18]. The observation that MFC could be used in paper coating formulations, as a co-binder, since it is biodegradable and has good shear thinning properties, raises a question about the processability of MFC coatings in a high speed coating process(above 1000m/min) [12]. This work focuses on determining general rheological and dewatering behavior of coating colors that contain MFC fibers used as co-binders. A thickener is added to prevent an excessive loss of water from coating color into the base paper and to adjust the rheological properties of the color, a thickener is usually added [03,28]. The physical and chemical properties of the thickeners differ, and they can be roughly divided into synthetic and natural polymers [01]. Water retention and immobilization are the key properties for successful paper coating formulations [21,05]. The task of research is to evaluate how the replacement of CMC co-binder with MFC material influences the viscoelastic and dewatering properties of the coating color [07]. Correlation of the data matrix obtained from dewatering, low-shear viscoelastic and immobilization time measurements show that there is a pattern providing general understanding of the MFC fiber performance in coating suspensions. It is important to understand what the typical behavioral pattern of all MFC coatings would be once they are in the coating process. A key characteristic of the response of a viscoelastic material, as are coating colors, to its deformation during dynamic process, is its ability to recover after cessation of the force which causes deformation [13,04]. Pigment reactivity with binders and co binders has an important effect in viscoelastic behavior of coating color. It has been proved through many previous research papers that more elastic structures of clay coatings yield larger elastic modul than the carbonate coatings [05,14].

On the use of colour in experimental fluid mechanics

This paper discusses how colour is used in experimental fl uid fl ow studies. Firstly, colour (defi ned scientifi cally by the wavelength of the light) can be used to discriminate between different channels in optical instrumentation, making it possible to measure several fl ow properties, simultaneously, and without any intrusion into the fl ow. These aspects of modern fl ow measurement are discussed in terms of some examples. Alternatively, the results of the fl ow measurement may be represented in the form of images, graphs and three-dimensional schematics with colour being used to identify and emphasise particular features that might otherwise remain concealed. The experimental results presented in the paper confi rm that using colour to discriminate between sets of data has several important advantages over the older black and white or grey scale forms of representation. Not only do colours provide an excellent basis for communication through graphical and three-dimensional presentations, but the resulting clarity may also help to reveal complex forms of flfl ow behaviour. Moreover, the inherent artistic appeal of some colour representations can draw the viewer into the technical detail, helping to simplify physical phenomena in ways that would not otherwise be possible. Although the observations made on the presentation of data are illustrated with reference to a number of experimental fl uid fl ow problems, many of the methods and observations would be applicable in other situations, where scientifi c or technological data needs to be presented.

Sensitivity to the Smagorinsky Constant in Turbulent Jet Simulations

the model’ s sensitivity by applying it to the LES of turbulent jets and analyzing the results of two simulations obtained with slightly direrent values of the model constant. The Smagorinsky model is known to be sensitive to values of the model constant; however, our simulations show explicitly how strongly the mean e ow properties of the jets are sensitive to the value of the model constant. More detailed results can be found in Ref. 5. Governing Equations

Supersonic Combustion Experiments with a Cavity-Based Fuel Injector

Recent results from combustion experimentsin a direct-connectsupersoniccombustorarepresented. Successful ignition and sustained combustion of gaseous ethylene have been achieved using an injector/e ameholder concept with low-angle, e ush-wall fuel injection upstream of a wall cavity. Two interchangeable facility nozzles (Mach 1.8 and 2.2) were used to obtain combustor inlet e ow properties that simulate e ight conditions between Mach 4 and 6 at a dynamic pressure of 47.9 kPa. Mainstream combustion was achieved at equivalence ratios between 0.25 and 0.75 using only a spark plug and no other external ignition aids. Delta-force levels between 667 and 1779 N were measured, with corresponding combustor pressure ratios between 3.1 and 4.0. Video records of the e ame zone show an intensely active combustion zone with rapid e ame spreading. One-dimensional performance analysis of the test data indicates a combustion efe ciency around 80% with an average combustor skin friction coefe cient of 0.0028.

Near-Wake Measurements of a Delta Wing in a Supersonic Stream

The near-wakeregion of a 75-deg sweptback delta wing wasstudied experimentally in a Mach 2.49 stream. Fivehole conical probe measurements were conducted vertically and horizontally through the primary vortices at the trailing edgeand half-chord downstream oftheplanformfor7-and 12-deg anglesofattack.TheMachnumberand pressure distribution proe les are summarized, and comparisons of e ow properties at different survey stations are presented. A novel calibration approach using a three-dimensional Navier ‐Stokes solver to generate numerically the calibration data for a blunt-nosed e ve-hole conical probe over a range of Mach numbers and pitch angles was employed.Themagnitudeofthepitot,total,andstaticpressuredee citsinthewakeregionincreasedwithincreasing angle of attack for the same measurement plane and decreased with the downstream distance. The swirl proe les have supersonic and high transonic peak magnitudes, and estimated core dimensions suggest vortex stretching in the vertical direction and convection downstream. A decrease in the radial Mach number component cone rms the vortex trajectory changes from a strong downward e ow over the planform to a gradual return toward the freestream in the near wake. Unlike the experimental results from transonic and low-speed leading-edge vortices, the axial and total Mach number distributions in supersonic vortices are found to be wakelike.

Two-Dimensional Nonadiabatic Injection into a Supersonic Freestream

Turbulence and mean e ow measurements were acquired downstream of a normal, supersonic (Mach 1.6), twodimensional, slot injection into Mach 2.9 e ow (Re/m=16 £ 10 6).An adiabatic (Tti/Tt1 =1.0)and two nonadiabatic injection cases (Tti/Tt1 =1.11andTti/Tt1 =0.93)werestudied.Multiple-overheatcross-e lmanemometryandconventional mean e ow probes, as well as instantaneous schlieren photography, were utilized to study the turbulent mixing layer. The mean e ow data included the pitot, cone-static, and Mach number proe les. The measured turbulence data included Reynolds shear stresses and turbulence intensities (mass e ux and total temperature ). The e ow visualizations highlighted the physical phenomena of the e ow as well as the associated turbulent structure that existed in the mixing layer. The injection and wall temperature were found to have a strong ine uence on the near wall (the bottom-half of the mixing layer relative to the wall ) mean and statistical turbulent e ow properties.

Effect of Nonspherical Shape on Oscillations of Levitated Droplets

substrates are on the order of 10 i10 and 10 i11 m 2 , respectively. 2 From the experimental data, it is clear that silicone resin impregnation of FRCI-12 restricts internal gas e ow much more than phenolic resin impregnation of FiberForm. There are several possible mechanisms to explain this. First, pressure-driven internal mass e ow in a porousmaterialscalestothethirdpower (atleast)withthecharacteristic channel dimension. Thus, comparable resin loadings into substrates with comparable densities are expected to cause greater e ow restrictions in the material with the e ner microstructure. Secondly, whileresin impregnationpredominantlycoatsthe e bers,some webbing between e bers is possible and has been observed in scanning electron microscope images. Such webbing would be more likely in the e ner microstructure substrate (FRCI-12) and may contribute to the very low continuum permeability of virgin SIRCA. For PICA specimens, the continuum permeability is larger and the slip parameter is smaller (on average) along in-plane directions than along transverse directions. This result is consistent with the anisotropicmicrostructureoftheFiberFormsubstrate,whichcauses the e ow path to be less tortuous and the mean distance between gas-surface collisions to be longer along in-plane directions than transversedirections. 2 ThoughFRCI-12substrateshavemicrostructural anisotropies similar to FiberForm, the transverse permeabilities of the virgin SIRCA specimens are found to be comparable with or greater than the in-plane permeabilities. This e nding gives further evidence that the internal e ow properties of virgin SIRCA are dominated by the microstructural changes produced by resin impregnation. Asexpected fromthe mass loss accompanying pyrolysis, charred specimensofbothPICAandSIRCAofferlessobstructiontothee ow than virgin specimens. For PICA specimens, the relative changes in K0 and b due to the pyrolysis process are larger for the transversely oriented specimens than the in-plane oriented specimens. This result is consonant with the view that resin is likely to agglomerate or web at e ber intersections during impregnation. Because e bers are preferentially oriented normal to the transverse direction, agglomerations at e ber intersections would offer more obstruction to transverse e ow than in-plane e ow, and charring would thus have a greater effect on transverse than in-plane permeability. The continuum permeability changes dramatically for SIRCA specimens upon charring, increasing by three orders of magnitude. Moreover, the underlying anisotropy of the FRCI-12 substrate is recovered; in-plane oriented specimens of charred SIRCA are about twice as permeable as transversely oriented specimens.

Experimental Investigation of the Role of Downstream Ramps on a Supersonic Injection Plume

An experimental study was conducted to investigate penetration and plume expansion enhancement of a discrete low-angled (25 deg) supersonic (M =1.9) injection into a supersonic (M =2.9) crosse ow. The enhancement was achieved by injecting the low-angled jet parallel to a compression ramp. Seven compression ramp cone gurations were studied. The jet-ramp interaction enhancement mechanisms included baroclinic torque vorticity, ramp spillage vorticity, bulk compression, and the Magnus force. Shadowgraph photography was used to identify shock structures. Measurements of mean e ow properties quantie ed the e owe eld total pressure losses. Mie scattering images were used to qualitatively assess the e owe eld and to quantify the plume size, trajectory, and concentration decay rate. The results indicated that up to a 22% increase in penetration, a 39% plume expansion (» mixing), and a 27% increase in the concentration decay rate, with a corresponding 17% increase in total pressure loss, can be achieved by injection over a compression ramp as compared with low-angled injection alone.

Computational Simulation of Emission Spectra from Shock-Layer Flows in an Arcjet Facility

This paper reports computational comparisons with experimental studies of a nonequilibrium bluntbody shock-layer e ow in a high-enthalpy arcjet wind tunnel at NASA Ames Research Center. The experimental data include spatially resolved emission spectra of radiation emanating from a shock layer formed in front of a e at-faced cylinder model. Multitemperature nonequilibrium codes are used to compute the conical nozzle e ow, supersonic jet, and shock-layer e ow. A line-of-sight (LOS) radiation code is employed to predict the spectra from the computed e owe eld. Computed LOS emission intensities are directly compared with the experimental data at several axial locations along the stagnation streamline. Various LOS-averaged e ow properties, such as vibrational and rotational temperatures, and species number densities, deduced from the experimental spectra, are compared with computed results. Comparisons provide an assessment of thermochemical equilibration processes in an arcjet shock layer.

Extensive Validation of a Monte Carlo Model for Hydrogen Arcjet Flowfields

A particle-based Monte Carlo numerical method is applied for the e rst time to model the nozzle and plume e ows of a low-thrust hydrogen arcjet. Starting from a continuum solution of the e ow just downstream of the constrictor, the present analysis employs the direct simulation Monte Carlo technique to compute the nonequilibrium e uid mechanics and thermochemical relaxation. Simulation of plasma e eld effects is included at a simple level using charge neutrality. A model is implemented to include ohmic heating in the simulation. Results are presented for two different arcjet e ow conditions. Comparisons of Monte Carlo results with experimental measurements for a variety of e owe eld properties are made in the nozzle interior, the nozzle exit plane, and the near-e eld plume e ow. Comparison of prediction with measurement is also made for thruster performance. For almost all e ow properties, good agreement is obtained between simulation and measurement. This indicates that the Monte Carlo model is a viable approach for optimization of arcjet performance, and for the prediction of spacecraft interaction effects.

Assessment of Jet Noise Analysis Codes for Multistream Axisymmetric and Forced Mixer Nozzles

Jet noise effects produced by an axisymmetric multistream exhaust nozzle have been examined using computational and experimental techniques. The current approach for designing low noise exhaust systems uses empirical rules and computational e uid dynamics (CFD) calculations aimed at lowering peak velocities and/or temperatures. Engineers need to be able to predict noise directly and use predictions to support their specie c design goals. The computational approach utilized in this paper applies a state-ofthe-art CFD Navier ‐ Stokes analysis (NASTAR), in conjunction with a computationally based aeroacoustics analysis. The aeroacoustic analysis uses mean e ow properties and turbulent kinetic energy/ dissipation variables as input parameters for the aeroacoustic solver. Predictions have been made and compared to experimental data obtained in NASA Lewis Research Center’ s open-jet facility. More specie cally, comparisons of aerodynamic and acoustic parameters have been made for axisymmetric nozzles to identify the effects of turbulence level, compressibility, geometrical sizing, and forward e ight on measured levels of jet noise. Applicability of this analysis approach to three-dimensional forced mixer cone gurations has also been explored, with a limited degree of success.

Analytical Study of the Oblique Reflection of Detonation Waves

The governing equations relating the e ow properties across an oblique detonation wave were reconsidered and modie edby accounting fordifferentheatcapacity ratiosonbothsideofthedetonation wave. Using theseequations, modie ed two- and three-shock-theory-based models were developed and applied to the ree ection of detonation waves. The present model makes it possible to investigate the behavior of detonation wave ree ections near and at the Chapman ‐Jouguet (CJ) point. It was shown that the properties of detonation waves near the CJ point are very sensitiveto the value of the overdrive. Theanalytical resultswere compared with experimental and numerical results from various laboratories, and in general, good agreement was obtained.