The Experts below are selected from a list of 252 Experts worldwide ranked by ideXlab platform

Alvaro T. Prata - One of the best experts on this subject based on the ideXlab platform.

  • analytical solution of single screw extrusion applicable to intermediate values of screw channel aspect ratio
    Journal of Food Engineering, 2009
    Co-Authors: Marcus Vinicius C Alves, Jader R. Barbosa, Alvaro T. Prata
    Abstract:

    The purpose of this work is to advance an alternative analytical solution of the pure Drag Flow in single screw extruders which is also applicable to intermediate values of the screw channel cross-section aspect ratio. The model is based on that of Li and Hsieh [Li, Y., Hsieh, F., 1996. Modeling of Flow in a single screw extruder. Journal of Food Engineering 17, 353–375] for the isothermal Flow of a Newtonian fluid in a small curvature screw channel where the motion of the screw flights are taken into account in the boundary conditions. The resulting boundary value problem was solved analytically via the generalized integral transform technique (GITT). The model was validated against other models available in the open literature. The effect of parameters related with the screw geometry, i.e., the aspect ratio, the curvature ratio and the helix ratio, on the down channel Flow rate is also explored in the manuscript.

Ganeshkumar A. Subramanian - One of the best experts on this subject based on the ideXlab platform.

  • Process Analytical Technology for High Shear Wet Granulation: Wet Mass Consistency Reported by In-Line Drag Flow Force Sensor Is Consistent With Powder Rheology Measured by At-Line FT4 Powder Rheometer®
    Journal of pharmaceutical sciences, 2016
    Co-Authors: Ajit S. Narang, Valery Sheverev, Tim Freeman, Douglas Both, Vadim Stepaniuk, Michael Delancy, Doug Millington-smith, Kevin Macias, Ganeshkumar A. Subramanian
    Abstract:

    Drag Flow force (DFF) sensor that measures the force exerted by wet mass in a granulator on a thin cylindrical probe was shown as a promising process analytical technology for real-time in-line high-resolution monitoring of wet mass consistency during high shear wet granulation. Our previous studies indicated that this process analytical technology tool could be correlated to granulation end point established independently through drug product critical quality attributes. In this study, the measurements of Flow force by a DFF sensor, taken during wet granulation of 3 placebo formulations with different binder content, are compared with concurrent at line FT4 Powder Rheometer characterization of wet granules collected at different time points of the processing. The wet mass consistency measured by the DFF sensor correlated well with the granulation's resistance to Flow and interparticulate interactions as measured by FT4 Powder Rheometer. This indicated that the force pulse magnitude measured by the DFF sensor was indicative of fundamental material properties (e.g., shear viscosity and granule size/density), as they were changing during the granulation process. These studies indicate that DFF sensor can be a valuable tool for wet granulation formulation and process development and scale up, as well as for routine monitoring and control during manufacturing.

David I. Bigio - One of the best experts on this subject based on the ideXlab platform.

  • comparison of scale up methods for dispersive mixing in twin screw extruders
    Polymer Engineering and Science, 2017
    Co-Authors: Ben Dryer, Graeme Fukuda, Jake Webb, Kyle Montemayor, Paul Andersen, David I. Bigio, Mark Wetzel
    Abstract:

    Twin-screw extrusion processes are commonly refined on laboratory-scale extruders then scaled-up to manufacturing systems. When using twin-screw extrusion to compound filler into a polymer, the dispersion of the filler must be considered during scale-up. In this work, two scale-up methods are evaluated for how accurately they scale dispersion as measured by the Residence Stress Distribution, an experimental method that quantifies stress developed in a twin-screw extruder. The first scale-up method evaluated is the industry-standard scaling based on maintaining equivalent volumetric Flow rate across extruder sizes. Volumetric scaling is compared to a second, novel scale-up method, the percent Drag Flow rule, which maintains the same degree of fill in the strongest dispersive screw elements on all extruder sizes. Both scale-up rules have been used to scale between three extruder sizes and have been evaluated for how accurately the larger extruders recreate the dispersive mixing of the smallest machine. Results indicate that the percent Drag Flow scale-up more accurately maintains dispersive mixing behavior than the volumetric scaling. Furthermore, percent Drag Flow scale-up resulted in all three extruder sizes behaving similarly to changes in operating conditions. These results indicate that percent Drag Flow scale-up is a valid technique to scale real industrial processes. POLYM. ENG. SCI., 57:345–354, 2017. © 2016 Society of Plastics Engineers

  • Comparison of scale‐up methods for dispersive mixing in twin‐screw extruders
    Polymer Engineering & Science, 2016
    Co-Authors: Ben Dryer, Graeme Fukuda, Jake Webb, Kyle Montemayor, Paul Andersen, David I. Bigio, Mark D. Wetzel
    Abstract:

    Twin-screw extrusion processes are commonly refined on laboratory-scale extruders then scaled-up to manufacturing systems. When using twin-screw extrusion to compound filler into a polymer, the dispersion of the filler must be considered during scale-up. In this work, two scale-up methods are evaluated for how accurately they scale dispersion as measured by the Residence Stress Distribution, an experimental method that quantifies stress developed in a twin-screw extruder. The first scale-up method evaluated is the industry-standard scaling based on maintaining equivalent volumetric Flow rate across extruder sizes. Volumetric scaling is compared to a second, novel scale-up method, the percent Drag Flow rule, which maintains the same degree of fill in the strongest dispersive screw elements on all extruder sizes. Both scale-up rules have been used to scale between three extruder sizes and have been evaluated for how accurately the larger extruders recreate the dispersive mixing of the smallest machine. Results indicate that the percent Drag Flow scale-up more accurately maintains dispersive mixing behavior than the volumetric scaling. Furthermore, percent Drag Flow scale-up resulted in all three extruder sizes behaving similarly to changes in operating conditions. These results indicate that percent Drag Flow scale-up is a valid technique to scale real industrial processes. POLYM. ENG. SCI., 57:345–354, 2017. © 2016 Society of Plastics Engineers

  • A new scale-up approach for dispersive mixing in twin-screw compounding
    2015
    Co-Authors: Graeme Fukuda, Paul Andersen, David I. Bigio, Mark D. Wetzel
    Abstract:

    Scale-up rules in polymer processing are critical in ensuring consistency in product quality and properties when transitioning from low volume laboratory mixing processes to high volume industrial compounding. The scale-up approach investigated in this study evaluates the processes with respect to dispersive mixing. Demand of polymer composites with solid additives, such as carbon microfibers and nanotubes, has become increasingly popular. Dispersive mixing breaks down particles that agglomerate, which is paramount in processing composites because solid additives tend to collect and clump. The amount of stress imparted on the material governs the degree of dispersive mixing. A methodology has been developed to characterize the Residence Stress Distribution (RSD) within a twin-screw extruder in real time through the use of polymeric stress beads. Through this technique, certain mixing scale-up rules can be analyzed. The following research investigated two different scale-up rules. The industry standard for mixing scale-up takes the ratio of outer diameters cubed to convert the volumetric Flow rate from the smaller process to a Flow rate appropriate in the larger machine. This procedure then resolves both operating conditions since shear rate remains constant. The second rule studied is based on percent Drag Flow, or the fraction of pumping potential, for different elements along the screw configuration. The percent Drag Flow rule aims to bring greater focus to operating conditions when scaling-up with respect to dispersive mixing. Through the use of the RSD methodology and a Design of Experiment (DOE) approach, rigorous statistical analysis was used to determine the validity between the scale-up rules of argument.

  • Mixing characterization based on Drag Flow : Phase III: Effect of kneading blocks on a visco-elastic system
    Journal of Reinforced Plastics and Composites, 1999
    Co-Authors: Daniel M. Swann, David I. Bigio, Frederick L. Magnus, Christopher Kiehl
    Abstract:

    Many new product properties are being achieved by blending and alloying homopolymers or copolymers with a variety of additives, rather than by the creation of new polymer. This paper examines the effect of screw design and operating conditions on the final product properties for the blending of solid filler into a visco-elastic matrix. To accomplish this, a simple screw design is used and the spacing is changed between the kneading blocks. The spacing for the screw profiles vanes from 0 mm to 90 mm in increments of 30 mm. The material used is silica mixed into polyisoprene in a 43 mm co-rotating twin screw extruder. The polymer Mooney viscosity is higher in the 30 mm profile than the other profiles. The average molecular weight for the 30 mm tended to be the least for all of the profiles. In addition, the ribbon die on the end of the extruder acted as another mixing element and therefore it also had an effect on both viscosity and the molecular weight when it was taken off. The effect is more pronounced for lower Drag Flow rates than for higher.

  • A new approach to analyzing residence time and mixing in a co‐rotating twin screw extruder
    Polymer Engineering & Science, 1999
    Co-Authors: Glenn E. Gasner, David I. Bigio, Charles Marks, Fredrick Lewis Magnus, Christopher Kiehl
    Abstract:

    A series of experiments was conducted to determine what correlations exist between an experimental parameter, percent Drag Flow, and other parameters such as head, tail and mean residence time. Experimentation was carried out on two polymer systems, a model system of near-Newtonian fluid and a viscoelastic system of polyisoprene with several additives. To aid in the residence time analysis, data from three literature sources were cited and replotted. A family of residence time curves for a partially filled system can be combined into one curve by plotting the number of screw revolutions carrying the tracer to the extruder exit versus the percent Drag Flow. This method of plotting the data for each screw configuration estimates the mean residence time for any throughput and screw speed once a few data points are taken. In all four sets of experiments, the number of screw revolutions carrying the tracer to the exit decreases with increasing percent Drag Flow. The filled volume of the extruder was calculated from residence time data to show that percent Drag Flow is linearly related to extruder filled volume. When percent Drag Flow increased in the viscoelastic system the following results were recorded: fraction of polymer residence time spent in conveying elements increased, fraction of residence time spent in mixing elements decreased, polymer Mooney viscosity increased, number and weight average molecular weights increased and polydispersivity increased.

Nathan S. Hariharan - One of the best experts on this subject based on the ideXlab platform.

  • Dual Mesh CFD Solver Comparison of Low Mach Flow over the ROBIN Fuselage
    53rd AIAA Aerospace Sciences Meeting, 2015
    Co-Authors: Jennifer Abras, Nathan S. Hariharan
    Abstract:

    The ROtor Body INteraction (ROBIN) fuselage is used as a baseline test case for a computational fluid dynamic (CFD) study of dual mesh solver Drag prediction results for low Mach Flow. All of the predictions are compared not only to one another, but also to available wind tunnel data. Comparisons of integrated viscous and pressure Drag, Flow separation point, and centerline pressure distributions are analyzed. Parametric studies of the independent options available are investigated to identify the advantages and disadvantages of each method. Grid studies are also presented. The current effort specifically investigates comparisons of different CFD solvers that employ dual mesh methodologies. In this study, CREATE-AV TM HELIOS and CREATE-AV TM KESTREL are used. The features that make this dual mesh methodology advantageous include the efficiency of Cartesian based solvers, the availability of higher spatial accuracy, and the use of adaptive mesh refinement in the separated region.

  • CFD Solver Comparison of Low Mach Number Flow over the ROBIN Fuselage
    52nd Aerospace Sciences Meeting, 2014
    Co-Authors: Jennifer Abras, Nathan S. Hariharan
    Abstract:

    The ROtor Body INteraction (ROBIN) fuselage is used as a baseline test case for a computational fluid dynamic (CFD) study of solver Drag prediction results for low Mach Flow. All of the predictions are compared not only to one another, but also to available wind tunnel data. Comparisons of integrated viscous and pressure Drag, Flow separation point, and centerline pressure distributions are analyzed. Parametric studies of the independent options available within each code for low Mach Flow conditions are investigated. Grid studies are also presented. The final comparisons reveal that for the attached Flow regions all of the CFD codes predict approximately the same result. The differences occur when the Flow begins to separate aft of the fuselage. Benefits are gained when the viscous grid layers are merged from tetrahedrons into prisms, and when the incompressible option is employed. Higher spatial order of accuracy in the separated region is found to slightly improve the results.

Bharathram Ganapathisubramani - One of the best experts on this subject based on the ideXlab platform.

  • Turbulent Boundary Layers Over Multiscale Rough Patches
    Boundary-Layer Meteorology, 2019
    Co-Authors: Christina Vanderwel, Bharathram Ganapathisubramani
    Abstract:

    We experimentally investigate the effects of multiscale rough patches on the Drag and Flow structure of a fully rough turbulent boundary layer in a wind tunnel. Several patches containing both organized and randomized arrangements of cubes of multiple sizes are tested in order to study the dependence of Drag on the frontal solidity of the patch. The Drag of each patch is measured with a Drag balance for a range of Reynolds numbers, indicating a dependence of the Drag on the frontal solidity following the trend predicted by Macdonald et al. (Atmos Environ 32(11):1857–1864, 1998 ). One of the patches is also replicated with the smallest scales removed and measurements show that the smaller scales have negligible impact on the overall Drag. Flow fields in several cross-sections are captured using particle image velocimetry, and maps of the velocity deficit and increased turbulence activity in the wake of the patches are determined and used to define the extent of the internal boundary layer formed by each patch.