Effect of acoustic excitation on fiber-reinforced polypropylene and the influence on melt viscosity

2021 ◽  
Author(s):  
Michael Heinrich ◽  
Ricardo Decker ◽  
Paul Reindel ◽  
Katja Böttcher ◽  
Isabelle Roth-Panke ◽  
...  
Keyword(s):  
Time Course ◽  
Flow Behavior ◽  
Glass Fibers ◽  
Shear Thinning ◽  
Acoustic Energy ◽  
Mold Surface ◽  
Melt Viscosity ◽  
Technological Approach ◽  
Actuator System ◽  
Plastics Processing

AbstractThe paper describes a novel technological approach to influencing the rheological properties of thermoplastic materials exposed to acoustic energy. The flow behavior of polypropylene with different mass percentages of glass fibers is investigated in a parallel plate rheometer under high-frequency longitudinal excitation. The influence of oscillation frequency on the melt viscosity is explained by means of shear thinning criteria. The dependence of the oscillation shape using sinusoidal excitation on shear thinning as a function of different fiber reinforcement percentages is also investigated. A phenomenological view describes the mutually influencing parameters with regard to different material compositions and different excitation frequencies over the time course of the rheometric measurement. Interacting relationships are analyzed and discussed and the potential of the actuator system to influence the plastic melt is worked out. Based on this, a technological approach follows which describes the transfer of an oscillating mold surface to plastics processing methods, which, especially in the case of energy-intensive injection molding technology, leads to the expectation of possible resource efficiency in energy and material.

scholarly journals Rheological Behavior of Glycyrrhiza glabra (Licorice) Extract as a Function of Concentration and Temperature: A Critical Reappraisal

Foods ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1872
Author(s):  
Laleh Nasiri ◽  
Mohsen Gavahian ◽  
Mahsa Majzoobi ◽  
Asgar Farahnaky
Keyword(s):  
Experimental Data ◽  
Flow Behavior ◽  
Shear Thinning ◽  
Soluble Solids ◽  
Licorice Root ◽  
Rotational Viscometer ◽  
Unit Operations ◽  
Licorice Extract ◽  
Solids Content ◽  
First Time

In the present study, rheological properties of twelve different licorice root extracts were evaluated using a rotational viscometer as a function of soluble solids content (15–45 °Bx) and temperature (30–70 °C). Response Surface Methodology was used to understand the relationships between the parameters. The experimental data were then fit into mathematical models. The results, for the first time, revealed that the licorice solutions had non-Newtonian shear-thinning behaviors with flow behavior indexes of 0.24 to 0.91, depending on the licorice extract samples, temperature, and °Bx. These observations were different from those reported in the literature and the present study elaborated on reasons for such observations. Further, the shear-thinning behavior generally increased by increasing the °Bx and decreasing the temperature. In addition, the power-law model was found to be suitable for predicting the experimental data. The newly revealed information can be particularly important in designing the unit operations for licorice extract processing.

Experimental investigations and optimization of processibility of sheet moulding compound

2011 ◽  
Vol 31 (2-3) ◽  
Author(s):  
Bhaskara J.C. Babu ◽  
Sachin Waigaonkar ◽  
Amit Rajput
Keyword(s):  
Penetration Depth ◽  
Flow Behavior ◽  
Glass Fibers ◽  
Zinc Stearate ◽  
Experimental Investigations ◽  
Compression Moulding ◽  
Maturation Time ◽  
Moulding Process ◽  
Moulding Compound ◽  
Sheet Moulding Compound

Abstract Sheet moulding compound (SMC) is a combination of glass fibers and filled polyester resin. It is processed by a compression moulding process and finds extensive applications in structural, automotive, electrical and electronic industries. The compression moulding process is characterized by the flow behavior of SMC under heat and pressure in the press mould. This paper is focused on the prediction of ideal processibility conditions of SMC. The qualitative aspect of a properly thickened (matured) moulding compound could be seen from its tack-free nature, which was quantitatively calibrated in terms of penetration depth, measured by a specially constructed softness indicator. The weight (wt)% of calcium carbonate (CaCO3) as filler, magnesium oxide (MgO) as thickener, graphite (C) and zinc stearate [Zn (C18H35O2)2] (ZnSt) as lubricants along with the maturation time (Tm) were selected as process variables. Taguchi’s scheme of experimental design was adapted to perform the experiments. It was found that the higher levels of MgO and CaCO3 were favorable for a good penetration depth as well as a reduced maturation time. We have also found that a penetration depth of at least 5 mm was required for achieving good processability conditions of SMC. An optimization study was under taken to find the right blend of additives and fillers, at their minimal weights and in the least possible maturation time, to achieve the desired processability. This study is particularly useful in a production run to make moulded parts from SMC.

scholarly journals Numerical simulations of blood cell flow in non-Newtonian fluid

2020 ◽  
Vol 306 ◽  
pp. 01006
Author(s):  
Kazuhiro Shitara ◽  
Toru Hyakutake
Keyword(s):  
Blood Cell ◽  
Red Blood Cells ◽  
Newtonian Fluid ◽  
Red Blood Cell ◽  
Blood Cells ◽  
Cell Model ◽  
Flow Behavior ◽  
Shear Thinning ◽  
Mutual Interference ◽  
Axial Concentration

We investigated how non-Newtonian viscosity behavior affects the flow characteristics of blood cells. Our findings offer insight about how shear thinning affects the dispersion of liposome-encapsulated hemoglobin and red blood cells in blood. The lattice Boltzmann method was used for fluid calculations, and the rheological properties of the non-Newtonian fluid were modeled with power-law relationships. The deformable three-dimensional red blood cell model was applied. First, we investigated the effects of shear thinning on the flow behavior of single blood cell. Simulation results indicate that shear thinning promotes the axial concentration of red blood cells. Next, varied the hematocrit to see how mutual interference between blood cells affects flow. At low hematocrit, shear thinning clearly promotes the axial concentration of red blood cells. As the hematocrit increases, in contrast, mutual interference has a greater effect, which counteracts shear thinning so the red blood cell distribution resembles the distribution within a Newtonian fluid.

Rheological Behavior of Seed Gum from Cassia fistula

2019 ◽  
Vol 818 ◽  
pp. 16-20
Author(s):  
Wancheng Sittikijyothin ◽  
Khanaphit Khumduang ◽  
Keonakhone Khounvilay ◽  
Rattanaphol Mongkholrattanasit
Keyword(s):  
Shear Rate ◽  
Flow Behavior ◽  
Critical Concentration ◽  
Shear Thinning ◽  
Zero Shear Viscosity ◽  
Specific Viscosity ◽  
Cross Model ◽  
Linear Slope ◽  
Mechanical Spectra ◽  
Seed Gum

The C. fistula gums in aqueous solutions clearly exhibited shear-thinning flow behavior at high shear rate, however, at higher concentrations, pronounced shear thinning was observed. The value of zero shear viscosity [h0] was predicted by fitting Cross model. A plotting of specific viscosity at zero shear rate (hsp0) against coil overlap parameter (C[h]) was shown the linear slope of dilute and simi-dilute as 1.43 and 4.10, respectively, which found the critical concentration (C*) about 7.08/[h]. While, the mechanical spectra in the linear viscoelastic region of gum solutions showed the typical shape for macromolecular solutions.

Shear thinning of the bulk metallic glass forming alloy Zr41.2 Ti13.8 Cu12.5 Ni10.0 Be22.5 close to the liquidus temperature.

2003 ◽  
Vol 806 ◽  
Author(s):  
Tyler Shaw ◽  
Christopher Way ◽  
Ralf Busch
Keyword(s):  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Power Law ◽  
Liquidus Temperature ◽  
Flow Behavior ◽  
Shear Thinning ◽  
Shear Rates ◽  
Glass Forming ◽  
Power Law Index ◽  
Type Response

ABSTRACTThe viscous properties of the multi component Zr41.2 Ti13.8 Cu12.5 Ni10.0 Be22.5 bulk metallic glass forming alloy was studied above the liquidus temperature. A shear thinning behavior for the molten alloy has been discovered. The shear thinning behavior can be characterized as a power law fluid with a power-law index of -0.5. Additionally, at low shear rates and temperatures near the liquidus temperature a visco-elastic type response in the flow behavior is observed.

Non-Newtonian Fluid Flow and Heat Transfer in a Semicircular Microtube Induced by Electroosmosis and Pressure Gradient

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Mehdi Karabi ◽  
Ali Jabari Moghadam
Keyword(s):  
Nusselt Number ◽  
Pressure Gradient ◽  
Flow Behavior ◽  
Velocity Ratio ◽  
Shear Thinning ◽  
Fluid Viscosity ◽  
Flow Behavior Index ◽  
Shear Thinning Fluids ◽  
Power Law Fluids ◽  
Behavior Index

The hydrodynamic and thermal characteristics of electroosmotic and pressure-driven flows of power-law fluids are examined in a semicircular microchannel under the constant wall heat flux condition. For sufficiently large values of the electrokinetic radius, the Debye length is thin; the active flow within the electric double layer (EDL) drags the rest of the liquid due to frictional forces arising from the fluid viscosity, and consequently a plug-like velocity profile is attained. The velocity ratio can affect the pure electrokinetic flow as well as the flow rate depending on the applied pressure gradient direction. Since the effective viscosity of shear-thinning fluids near the wall is quite small compared to the shear-thickening fluids, the former exhibits higher dimensionless velocities than the later close to the wall; the reverse is true at the middle section. Poiseuille number increases with increasing the flow behavior index and/or the electrokinetic radius. Due to the comparatively stronger axial advection and radial diffusion in shear-thinning fluids, better temperature uniformity is achieved in the channel. Reduction of Nusselt number continues as far as the fully developed region where it remains unchanged; as the electrokinetic radius tends to infinity, Nusselt number approaches a particular value (not depending on the flow behavior index).

A Computational Study of Enhanced Heat Transfer in Laminar Flows of Non-Newtonian Fluids in Corrugated-Plate Channels

2000 ◽  
Author(s):  
Hossam M. Metwally ◽  
Raj M. Manglik
Keyword(s):  
Heat Transfer ◽  
Computational Study ◽  
Flow Behavior ◽  
Shear Thinning ◽  
Swirl Flow ◽  
Laminar Flows ◽  
Enhanced Heat Transfer ◽  
Uniform Wall Temperature ◽  
Wide Range ◽  
Uniform Wall

Abstract The enhanced heat transfer behavior of laminar shear-thinning, power-law fluid flows in sinusoidal corrugated-plate channels is investigated. With duct plates at uniform wall temperature, periodically developed flows are considered for a wide range of channel corrugation aspect ratio (0 ≤ γ ≤ 1), flow rates (10 ≤ Reg ≤ 1500), and pseudo-plastic flow behavior indices (n = 0.5, 0.8, and 1.0). Typical velocity and temperature distributions, along with extended results for isothermal friction factor f and Collburn factor j are presented. The enhanced forced convection is found to be strongly influenced by γ, and the flow field displays two distinct regimes: undisturbed laminar or no swirl, and swirl flow regimes. In the no-swirl regime, behavior similar to that in fully developed straight duct flows with no cross-stream disturbance is obtained. The shear-thinning nature of the fluid, however, decreases f and enhances j. In the swirl regime, flow separation and reattachment in the corrugation troughs generates transverse vortices that grow with Reg and γ. The transition to this regime is also seen to depend on Reg, γ, and n, and in shear-thinning flows, it occurs at a lower Reg. The combined effects of corrugated plate geometry and non-Newtonian fluid rheology produce a heat transfer enhancement, as measured by the factor j/f, of over 3.3 times that in a flat-plate channel depending upon γ, n, and Reg.

Inflow Conditions and the Flow Behavior of a Biofluid in a Separated Flow Region

2014 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Velocity Profile ◽  
Flow Behavior ◽  
Separated Flow ◽  
Flow Region ◽  
Shear Thinning ◽  
Inflow Velocity ◽  
Flow Restriction ◽  
Upstream Flow ◽  
Inflow Conditions ◽  
Region Size

Inflow conditions influence on the flow behavior of human blood in a separated and reattached flow region is investigated. Hemorheological data that account for the yield stress and shear-thinning non-Newtonian characteristics of blood are used. The governing mass and momentum conservation equations along with the Herschel-Bulkley constitutive equation are solved numerically using a finite-difference scheme. Two inflow velocity profiles are considered, uniform and fully-developed ones. A parametric study is performed to reveal the impact of inflow velocity profile, upstream flow restriction, and rheology on the recirculation strength and reattachment characteristics of the flow field. Uniform inflow conditions result in larger relative recirculation intensity, in comparison with the fully-developed ones, only for a moderate upstream flow restriction. The separated flow region size in the case of a fully-developed inflow is always smaller than the one observed for uniform inflow. Larger separated flow regions with stronger flow recirculation, are predicted by the Newtonian model in comparison with the yield shear-thinning model for all studied inflow and upstream restriction conditions. The separated flow region size displays a strong dependency on the inflow velocity profile and upstream flow restriction, in comparison with the observed dependency on the used hemorheological model.

Fluid dynamic analog experiments on “Pele’s hair” using a handmade cotton candy machine

2020 ◽  
Author(s):  
Ichiro Kumagai ◽  
Miyuki Yamada
Keyword(s):  
Formation Process ◽  
High Speed ◽  
Heating Temperature ◽  
Fluid Dynamic ◽  
Flow Behavior ◽  
Glass Fibers ◽  
Volcanic Glass ◽  
Rotating Disk ◽  
Rotating Speed ◽  
Cotton Candy

<p>On the south flank of Kilauea volcano in Hawaii Island, we will find glass fibers called “Pele’s hair” in the volcanic products of lava fountains and explosions. It is named after Pele, who is the Hawaiian goddess of volcanos. “Pele’s hairs” are highly stretched volcanic glass products, which are formed by breakup, stretching, and cooling of molten magma during their eruption. The texture of the glass fibers (thickness and length of fibers) depend on many parameters such as rheological properties of the volcanic glass, cooling rate, ejection speed, wind velocity, and so on. In order to consider the formation process of “Pele’s hair” in classroom experiments, we developed a handmade cotton candy maker. We used a commercial stirrer which could control the rotating speed. At the edge of the stirrer, we attached a rotating dish, which was made of thin steel and had small outlets along its periphery. To make fibers of sugars (threads of cotton candy), crystal sugar (“Za-ra-me” in Japanese, coarse sugar) was added to the dish and rotated at a constant speed. The melted sugar was formed after heating the rotating disk and ejected through the outlets. We measured the temperature of the melted sugar by a commercial radiation thermometer and the flow behavior of the melted sugar jet was captured by a high-speed video camera, which helped us to understand the formation process. By controlling the rotating speed, heating temperature and diameter of the outlets, we have succeeded in producing a variety of analog “Pele’s hair” and Pele’s tear”. We carefully examined the texture of the analogue Pele’s products and discussed the role of these controlling parameters on their formation process. In this presentation, we will also discuss the similarity of the texture of Pele’s hairs, which were sampled from volcanic products in Hawaii Islands, with the analog Pele’s hairs of cotton candy using a commercial digital microscope.</p>

Computational Modeling of Enhanced Laminar Flow Heat Transfer in Viscoplastic Fluids in Corrugated-Plate Channels

2002 ◽  
Author(s):  
Hossam M. Metwally ◽  
Raj M. Manglik
Keyword(s):  
Heat Transfer ◽  
Yield Stress ◽  
Power Law ◽  
Flow Behavior ◽  
Shear Thinning ◽  
Bingham Plastic ◽  
Wide Range ◽  
Order Of Magnitude ◽  
Colburn Factor ◽  
Power Law Index

The enhanced heat transfer in laminar viscoplastic, shear thinning, Herschel-Bulkley fluid flows in sinusoidal corrugated-plate channels is investigated. With uniform-temperature plate walls, periodically developed flows are considered for a wide range of flow rates (10 ≤ Reg ≤ 700) and pseudoplastic flow behavior indices (n = 0.54, 0.8, and 1.0; the latter representing a Bingham plastic). The effects of fluid yield stress are simulated for the case where τy = 1.59 N/m2, representing a 0.5% xantham gum aqueous solution. Typical velocity and temperature distributions, along with extended results for isothermal friction factor ƒ and Colburn factor j are presented. The effect of the yield stress is found to be most dominant at low Reg regardless of the power law index n, and the recirculation or swirl in the wall trough regions is weaker than in the cases of Newtonian and power-law liquids. At higher Reg, the performance of the Herschel-Bulkley fluid asymptotically approaches that of the non-yield-stress power-law fluid. At low Reg, the yield stress increases ƒ by an order of magnitude and j is enhanced because of the higher wall gradients imposed by the plug-like flow field. The relative heat transfer enhancement, represented by the ratio (j/ƒ), and the role of the fluid yield stress and shear-thinning (or pseudoplastic) behaviors are also discussed.

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