scholarly journals Electroosmotic Mixing of Non-Newtonian Fluid in a Microchannel with Obstacles and Zeta Potential Heterogeneity

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 431
Author(s):  
Lanju Mei ◽  
Defu Cui ◽  
Jiayue Shen ◽  
Diganta Dutta ◽  
Willie Brown ◽  
...  
Keyword(s):  
Zeta Potential ◽  
Newtonian Fluid ◽  
Stokes Equations ◽  
Flow Behavior ◽  
Vortical Flow ◽  
Mixing Efficiency ◽  
Flow Behavior Index ◽  
Fluid Field ◽  
Electric Double Layer Thickness ◽  
Behavior Index

This paper investigates the electroosmotic micromixing of non-Newtonian fluid in a microchannel with wall-mounted obstacles and surface potential heterogeneity on the obstacle surface. In the numerical simulation, the full model consisting of the Navier–Stokes equations and the Poisson–Nernst–Plank equations are solved for the electroosmotic fluid field, ion transport, and electric field, and the power law model is used to characterize the rheological behavior of the aqueous solution. The mixing performance is investigated under different parameters, such as electric double layer thickness, flow behavior index, obstacle surface zeta potential, obstacle dimension. Due to the zeta potential heterogeneity at the obstacle surface, vortical flow is formed near the obstacle surface, which can significantly improve the mixing efficiency. The results show that, the mixing efficiency can be improved by increasing the obstacle surface zeta potential, the flow behavior index, the obstacle height, the EDL thickness.

A Comparative Analysis of Mixing Performance of Power-Law Fluid in Cylindrical Microchannels With Sudden Contraction/Expansion

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
A. Banerjee ◽  
A. K. Nayak ◽  
B. Weigand
Keyword(s):  
Pressure Drop ◽  
Power Law ◽  
Flow Behavior ◽  
Geometric Parameters ◽  
Mixing Efficiency ◽  
Flow Behavior Index ◽  
Mixing Performance ◽  
Geometric Configurations ◽  
Wide Range ◽  
Behavior Index

Abstract This paper focuses on the comparative electrokinetic micromixing of non-Newtonian fluid in cylindrical microchannels with surface potential heterogeneity due to sudden constriction/expansion. In numerical simulations, the rheology of the aqueous solution is considered to follow power-law characteristic. Based on the Poisson–Nernst–Planck model, the simulations are performed to investigate the mixing efficiency and pressure drop for constricted and expanded configurations over a wide range of the flow behavior index, potential patch strength, and geometric parameters. The results show that, irrespective of geometric configurations, the mixing efficiency can be improved significantly by increasing the flow behavior index, geometric parameters, and the overpotential patch strength. In addition, it is also revealed that the constricted geometry yields better mixing as compared to the other configuration, but the average pressure drop shows reverse characteristics. Thus, a parametric relationship is tried to be established between mixing efficiency and pressure drop for both these configurations to propose an effective and efficient micromixer, which can produce maximum possible mixing efficiency with minimum pressure drop.

Effects of Greek Pomegranate Extracts in the Antioxidant Properties and Storage Stability of Kefir

2019 ◽  
Vol 15 (4) ◽  
pp. 437-441 ◽  
Author(s):  
Vasiliki Lagouri ◽  
Georgia Dimitreli ◽  
Aikatarini Kouvatsi
Keyword(s):  
Antioxidant Activity ◽  
Dairy Products ◽  
Storage Time ◽  
Storage Stability ◽  
Flow Behavior ◽  
Antioxidant Properties ◽  
Flow Behavior Index ◽  
Ph Values ◽  
Dpph Activity ◽  
Behavior Index

Background: Oxidation reactions are known to shorten the shelf life and cause damage to foods rich in fat, such as dairy products. One way to limit oxidation and increase the shelf life of fermented dairy products is to use natural antioxidants. The aim of this study was to examine the effect of adding pomegranate extracts in the antioxidant properties, rheological characteristics and the storage stability of the fermented product of kefir. Methods: The Pomegranate Juice (PGJ) and Peel Extracts (PGPE) (5%, 10% w/v) were added to kefir and the antioxidant properties were evaluated by using the methods of radical scavenging activity (DPPH) and Ferric Reducing Antioxidant Power Activity (FRAP). Spectrophotometric and instrumental methods were used to determine the Total Phenols (TPs), pH values, viscosity and flow behavioral index values of enriched with pomegranate kefir samples. The same properties were tested when kefir samples stored at 4°C for 7, 14, 21 and 28 days. Results: The addition of PGJ and PGPE results in an increase in the antioxidant activity (DPPH, FRAP) and total phenol content (TPs) of kefir samples. Increasing the concentration of the added PGJ and PGPE, results in an increase in the TP content and the DPPH activity of kefir. As far as the storage time is concerned, the results showed an increase in the amount of TP at 7th day and a reduction in the DPPH activity in the 14th day of storage. In contrary to the DPPH method, the increase in storage time has resulted in a reduction in antioxidant activity by the FRAP method. The addition of PGJ and PGPE in kefir results in a decrease in pH values while the pH of kefir samples increased during storage at 4°C for 28 days. The addition of PGJ and PGPE to kefir samples results to a decrease in viscosity and an increase in the flow behavior index. Increasing storage time results in increased flow behavior index of kefir samples. Conclusion: The addition of PGJ and PGPE increased the antioxidant activity and total phenols of the kefir product and preserved its properties during the total storage time of 28 days at 4°C.

Electroosmotic Flow of Power-Law Fluids in a Slit Microchannel

2009 ◽  
Author(s):  
Cunlu Zhao ◽  
Chun Yang
Keyword(s):  
Shear Stress ◽  
Double Layer ◽  
Power Law ◽  
Dynamic Viscosity ◽  
Electroosmotic Flow ◽  
Flow Behavior ◽  
Flow Behavior Index ◽  
Power Law Fluids ◽  
Hyperbolic Cosine ◽  
Behavior Index

Electroosmotic flow of power-law fluids in a slit channel is analyzed. The governing equations including the linearized Poisson–Boltzmann equation, the Cauchy momentum equation and the continuity equation are solved to seek analytical expressions for the shear stress, dynamic viscosity and velocity distributions. Specifically, exact solutions of the velocity distributions are explicitly found for several special values of the flow behavior index. Furthermore, with the implementation of an approximate scheme for the hyperbolic cosine function, approximate solutions of the velocity distributions are obtained. In addition, a mathematical expression for the average electroosmotic velocity is derived for large values of the dimensionless electrokinetic parameter, κH, in a fashion similar to the Smoluchowski equation. Hence, a generalized Smoluchowski velocity is introduced by taking into account contributions due to the finite thickness of the electric double layer and the flow behavior index of power-law fluids. Finally, calculations are performed to examine the effects of κH, flow behavior index, double layer thickness, and applied electric field on the shear stress, dynamic viscosity, velocity distribution, and average velocity/flow rate of the electroosmotic flow of power-law fluids.

Shear Rate Corrections for Herschel-Bulkley Fluids in Couette Geometry

2008 ◽  
Vol 18 (3) ◽  
pp. 34482-1-34482-11 ◽  
Author(s):  
Vassilios C. Kelessidis ◽  
Roberto Maglione
Keyword(s):  
Flow Behavior ◽  
Flow Equation ◽  
Oil Field ◽  
Rheological Parameters ◽  
Concentric Cylinder ◽  
Flow Behavior Index ◽  
Shear Rates ◽  
Power Law Fluids ◽  
Good Agreement ◽  
Behavior Index

AbstractA methodology is presented to invert the flow equation of a Herschel-Bulkley fluid in Couette concentric cylinder geometry, thus enabling simultaneous computation of the true shear rates, γ̇HB, and of the three Herschel-Bulkley rheological parameters. The errors made when these rheological parameters are computed using Newtonian shear rates, γ̇N, as it is normal practice by research and industry personnel, can then be estimated. Quantification of these errors has been performed using narrow gap viscometer data from literature, with most of them taken with oil-field rheometers. The results indicate that significant differences exist between the yield stress and the flow behavior index computed using γ̇HB versus the parameters obtained using γ̇N and this is an outcome of the higher γ̇HB values. Predicted true shear rates and rheological parameters are in very good agreement with results reported by other investigators, who have followed different approaches to invert the flow equation, both for yield-pseudoplastic and power-law fluids.

scholarly journals COMPORTAMENTO REOLÓGICO DE EXTRATOS DE GRÃOS, FARINHA INTEGRAL E ISOLADO PROTÉICO DE SOJA

2003 ◽  
Vol 21 (2) ◽  
Author(s):  
ROSANE DA SILVA RODRIGUES ◽  
ÂNGELA MARIA GOZZO ◽  
ROBERTO HERMÍNIO MORETTI
Keyword(s):  
Newtonian Fluid ◽  
Soy Protein ◽  
Apparent Viscosity ◽  
Flow Behavior ◽  
Total Solid ◽  
Soy Flour ◽  
Soluble Solids ◽  
Rheological Parameters ◽  
Flow Behavior Index ◽  
Isolated Soy Protein

Estudou-se o comportamento reológico de extratos elaborados com grãos, farinha integral e isolado protéico de soja. Extratos com 3% de proteína foram obtidos de grãos de soja (em equipamento conhecido como “vaca mecânica”), de farinha integral e de isolado protéico (por dissolução em água) e pasteurizados a 74±2°C por 15 seg. Os parâmetros reológicos estudados foram o coeficiente de consistência, o índice de comportamento do fluxo e a viscosidade aparente. Foram determinados, também, sólidos totais, proteínas, lipídios, cinzas, fibra bruta, carboidratos e índice de sedimentação (AOAC, 1995). Verificou-se que a viscosidade aparente, a 4 e 25°C, do extrato obtido de grãos de soja (fluido nãonewtoniano com comportamento pseudoplástico) foi maior que a do extrato da farinha (fluido não-newtoniano com comportamento pseudoplástico a 4°C e dilatante a 25°C) e do isolado (fluido newtoniano). O maior índice de sedimentação constatado no extrato de farinha integral e o baixo teor de sólidos solúveis no isolado protéico foram determinantes, entre outros fatores, no comportamento reológico verificado. AbstractRHEOLOGICAL BEHAVIOR OF SOYMILK, WHOLE SOY FLOUR AND SOY ISOLATED PROTEIN The rheological properties of extracts elaborated with soybeans, whole soy flour and isolated protein were studied. Extracts with 3% of protein were obtained from soybeans (in a equipment called “mechanic cow”), whole soy flour and isolated soy protein (by dissolution in water) and pasteurized at 74±2°C for 15 seg. The rheological parameters studied were the flow behavior index, consistency coefficient and apparent viscosity. Total solid, proteins, lipids, ashes, brute fiber, carbohydrates and sedimentation index (AOAC, 1995) was also determined. The apparent viscosity, at 4 and 25°C, of the extract obtained from soybeans (non-newtonian fluid with pseudoplastic behavior), was greater than the one of whole soy flour extract (nonnewtonian fluid with pseudoplastic behavior at 4°C and dilatant at 25°C) and of the isolated soy protein extract (Newtonian fluid). The highest sedimentation index verified in the whole soy flour extract and the low content of soluble solids in the extract of isolated soy protein defined, among others factors, the rheological behavior verified.

scholarly journals Initial Self-Healing Temperatures of Asphalt Mastics Based on Flow Behavior Index

Materials ◽  
2018 ◽  
Vol 11 (6) ◽  
pp. 917 ◽  
Author(s):  
Chao Li ◽  
Shaopeng Wu ◽  
Guanyu Tao ◽  
Yue Xiao
Keyword(s):  
Flow Behavior ◽  
Self Healing ◽  
Flow Behavior Index ◽  
Asphalt Mastics ◽  
Behavior Index

Non-Newtonian Flow Behavior on Frictional Pressure in Packed Bed

2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Suresh Kumar Patel ◽  
Subrata Kumar Majumder
Keyword(s):  
Pressure Loss ◽  
Liquid Velocity ◽  
Flow Behavior ◽  
Scale Up ◽  
Packed Bed ◽  
Newtonian Liquid ◽  
Newtonian Flow ◽  
Flow Behavior Index ◽  
Ergun Equation ◽  
Behavior Index

The packed bed columns with non-Newtonian liquid are increasing importance as a simple and inexpensive means of achieving yield of different chemical and biochemical processes though their hydrodynamic behavior is complex and not yet fully understood. In this article non-Newtonian flow behavior on frictional pressure was investigated in packed bed within a range of liquid velocity 0.004-0.04 m/s. The frictional pressure loss in non-Newtonian liquid system has been analyzed by modified Ergun equation. The modification of the Ergun equation is incorporated with the flow behavior index of non-Newtonian liquid. The degree of frictional pressure loss decreases with increase in flow behavior index. A correlation has been developed to interpret the degree of effect on the frictional pressure loss. The correlation may be useful for further understanding and scale-up of the packed bed column for its industrial application.

Rheological Properties of Butia Pulp

2006 ◽  
Vol 2 (1) ◽  
Author(s):  
Charles Windson Isidoro Haminiuk ◽  
Maria-Rita Sierakowski ◽  
Giselle Maria Maciel ◽  
José Raniere Mazile Bezerra Vidal ◽  
Ivanise Guilherme Branco ◽  
...  
Keyword(s):  
Yield Stress ◽  
Apparent Viscosity ◽  
Good Description ◽  
Flow Behavior ◽  
Rheological Parameters ◽  
Concentric Cylinder ◽  
Flow Behavior Index ◽  
Different Temperatures ◽  
Stress Flow ◽  
Behavior Index

Rheological parameters of Butia pulp were determined at different temperatures using a concentric cylinder Haake Rotovisco rheometer, model RV-20, with measurement system ZA-30. Butia pulp was found to exhibit non-Newtonian, pseudoplastic behavior at all temperatures and the rheological parameters were adequately described by the Herschel-Bulkley model. Yield stress, flow behavior index, and consistency coefficient were significantly affected by temperature. The yield stress decreased exponentially with process temperature and ranged between 36.60 and 21.70 Pa. Apparent viscosity calculated through the Herschel-Bulkley model decreased with an increase in temperature. The Arrhenius model gave a good description of temperature effect on apparent viscosity of the pulp.

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).

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