Significant enhancement of the electrorheological effect by non-straight electrode geometry

Soft Matter ◽  
2019 ◽  
Vol 15 (32) ◽  
pp. 6455-6460 ◽  
Author(s):  
X. Huo ◽  
G. Yossifon
Keyword(s):  
Apparent Viscosity ◽  
Significant Enhancement ◽  
Electrode Geometry ◽  
Electrorheological Effect ◽  
Order Of Magnitude ◽  
Er Fluid

In contrast to the commonly used straight electrodes with electrorheological (ER) fluid, here we studied the effect of non-straight electrodes where more than one order of magnitude enhancement of the apparent viscosity was observed.

A Novel Mechanism of Electrorheological Effect in Polymer Blends

1999 ◽  
Vol 13 (14n16) ◽  
pp. 1983-1989 ◽  
Author(s):  
H. Kito ◽  
K. Tajiri ◽  
H. Orihara ◽  
Y. Ishibashi ◽  
M. Doi ◽  
...  
Keyword(s):  
Liquid Crystalline Polymer ◽  
Liquid Crystalline ◽  
Crystalline Polymer ◽  
High Viscosity ◽  
Thin Layers ◽  
The Other ◽  
Parallel Plates ◽  
Low Viscosity ◽  
Electrorheological Effect ◽  
Er Fluid

We present a novel mechanism of an electrorheological (ER) effect found in a polymer blend of a liquid crystalline polymer (LCP) with high viscosity and a polydimethylsiloxane (DMS) with low viscosity. In this type of ER fluid thin layers of DMS are formed between the parallel plates of a viscometer and so the blends separated by them can slide on each other, resulting in the decrease of the apparent viscosity. Under an electric field, on the other hand, the area of the layers decreases and thus the ER effect appears.

The Streaming Potential and the Rheology of Foam

1967 ◽  
Vol 7 (04) ◽  
pp. 359-368 ◽  
Author(s):  
S.H. Raza ◽  
S.S. Marsden
Keyword(s):  
Porous Media ◽  
Apparent Viscosity ◽  
Streaming Potential ◽  
Newtonian Fluids ◽  
Flow In Porous Media ◽  
Flow Rates ◽  
Foaming Agents ◽  
Streaming Potentials ◽  
Foam Flow ◽  
Order Of Magnitude

Abstract An experimental study of the flow of fine-textured, aqueous foams through Pyrex tubes is described. The foams range in quality F (ratio of gas volume to total volume) from 0.70 to 0.96 and behave like pseudoplastic fluids. At lower flow rates they exhibit laminar flow and have apparent viscosities which increase with quality, and which cover a range of 15 cp to 255 poise for tubes of 0.25- to 1.50-mm radius ri. At higher flow rates a plug-like type of flow is developed, the extent of which increases with both and ri. When the same foams flow through either open or packed Pyrex tubes, remarkably high streaming potentials phi E are often generated. These can easily reach 50v if nonionic foaming agents are used, but are at least an order of magnitude less for ionic foaming agents. A linear relationship between phi E and the pressure differential phi p is observed; this usually extrapolates to positive values of phi p at phi E of zero. The slope of the line increases with both F and ri. An equation was derived to describe the streaming potential of non-Newtonian fluids in circular tubes and was used to correlate experimental results. The calculated potential is are of the right order of magnitude. Introduction Foams are both unusual and intriguing in their physical properties, and have been the subject of many scientific studies. However, present knowledge of foams is still fragmentary, specific and often contradictory. Apparent viscosity of foam is the physical property of greatest interest to both rheologists and engineers. Sibree reported that the apparent viscosity decreased with increasing shear rate in a manner similar to some non-Newtonian fluids. Penny and Blackman reported that fire-fighting foams had both a limiting shear stress and a tensile yield stress. There is little doubt that some foams at least behave like non-Newtonian fluids, and have apparent viscosities considerably higher than those of either constituent phase. The high apparent viscosity of foam with its concomitant effect on mobility ratio and sweep efficiency no doubt prompted several attempts by research groups to use foam as a displacing agent in porous media. Based on recent experience, most of these groups probably succeeded in completely blocking fluid flow in the porous media and then abandoned their efforts. Two groups apparently found the successful combination of experimental parameters at about the same time. Others have recently added to our knowledge-of foam flow in porous media and its use as a displacing agent. An experimental problem encountered by Fried was a transient blockage of foam flow in porous media when distilled water was used to prepare the foam-producing solution. Fried surmised that this was due to an electrokinetic effect and he eliminated it by using electrolytes in preparing foaming solutions. He also measured the streaming potential of a number of foams in capillary tubes which he found to be appreciably higher than those obtained when the constituent liquid flowed under comparable conditions. This paper presents results of a more comprehensive study of the streaming potential generated by aqueous foam flowing in both open and packed Pyrex tubes. It also adds to knowledge of the rheology of these foams as deduced from their flow behavior in open tubes. APPARATUS AND PROCEDURE A diagram of the apparatus used is shown in Fig. 1. Details of its construction, testing and use are described elsewhere. Careful selection of materials, extreme cleanliness and rather elaborate electrical insulation and shielding were necessary to obtain reproducible results (15 percent). Both streaming potential and streaming current were measured with an electrometer. The design of the foam generator developed for this work is novel (Fig. 2). SPEJ P. 359ˆ

Controllable Squeeze Film Damper: An Application of Electro-Rheological Fluid

1991 ◽  
Author(s):  
Shin Morishita ◽  
Jun’ichi Mitsui
Keyword(s):  
Apparent Viscosity ◽  
Vibration Mode ◽  
Squeeze Film ◽  
Damping Capacity ◽  
Flexible Rotor ◽  
Rotor Vibration ◽  
Squeeze Film Damper ◽  
Rotating Speed ◽  
Wide Range ◽  
Er Fluid

Abstract A notable characteristic of Electro-Rheological (ER) fluid is the variation of its apparent viscosity with the application of an electric field. The application of this characteristic to the performance of squeeze film damper of a flexible rotor is investigated in this paper. It is shown experimentally that by controlling the supporting damping capacity continuously, rotor vibration can be reduced remarkably in a wide range of rotating speed. Moreover, the study indicates experimentally that there exists an optimum supporting damping for every vibration mode.

Electrorheological Effect at Cryogenic Temperature

1999 ◽  
Vol 13 (14n16) ◽  
pp. 1697-1704 ◽  
Author(s):  
Tian-Jie Chen ◽  
X. Zhang ◽  
R. Tao
Keyword(s):  
Liquid Nitrogen ◽  
Room Temperature ◽  
Aluminum Particles ◽  
Low Viscosity ◽  
Electrorheological Effect ◽  
Flow Motion ◽  
Random Flow ◽  
Temperature Liquid ◽  
Er Fluids ◽  
Er Fluid

We have observed a strong electrorheologial (ER) effect of a suspension of fine aluminum particles in liquid nitrogen. The particles have diameter ~ 10μm and an insulate surface. In an ac field, aluminum particles quickly form chains across the two electrodes. The chains vibrate vigorously as the liquid nitrogen has a constant random flow motion caused by bubbles. In addition to low temperature, liquid nitrogen has extremely low viscosity, and low conductivity. These special properties enable us to observe several interesting phenomena which are absent in ER fluids at room temperature. We have determined the rheological properties of our cryogenic ER fluid.

Directionally Controllable Squeeze Film Damper Using Electro-Rheological Fluid

2001 ◽  
Vol 124 (1) ◽  
pp. 105-109 ◽  
Author(s):  
Young Kong Ahn ◽  
Bo-Suk Yang ◽  
Shin Morishita
Keyword(s):  
Electric Field ◽  
Yield Stress ◽  
Apparent Viscosity ◽  
Rotor System ◽  
Squeeze Film ◽  
Flexible Rotor ◽  
Squeeze Film Damper ◽  
Er Fluid

Electro-Rheological (ER) fluid is a class of functional fluid whose yield stress can be changed by an electric field applied to the fluid, which is observed as a variation of apparent viscosity. This functional fluid is applied to a controllable squeeze film damper (SFD) for stabilizing a flexible rotor system. In applying ER fluid to a conventional passive SFD, a pair of rings in the damper can be used as electrodes. When the electrodes are divided into a horizontal pair and a vertical one, the SFD can provide external damping in each direction independently. A prototype of the directionally controllable SFD was constructed and its performance was experimentally and numerically investigated in the present work.

Transient Response of an Immiscible Polymer Blend ER Fluid to a Step Electric Field

1999 ◽  
Vol 13 (14n16) ◽  
pp. 1990-1997
Author(s):  
Kozo Tajiri ◽  
Hiroshi Orihara ◽  
Yoshihiro Ishibashi ◽  
Masao Doi ◽  
Akio Inoue
Keyword(s):  
Shear Stress ◽  
Polymer Blend ◽  
Transient Response ◽  
Transient Responses ◽  
Immiscible Polymer Blend ◽  
Electrorheological Effect ◽  
Immiscible Polymer ◽  
Viscous Polymer ◽  
The Relationship ◽  
Er Fluid

The relationship between the electrorheological effect and the structure in an immiscible polymer blend was investigated in detail by observing the transient responses to a step field. It was clarified that the increase of the shear stress consists of two processes, the first and the second modes. The former may be ascribed to the elongation of droplets, and the origin of the latter is the formation of cylinders consisting of viscous polymer.

scholarly journals Micro-Textural Controls on Magma Rheology and Vulcanian Explosion Cyclicity

2021 ◽  
Vol 8 ◽  
Author(s):  
Amelia A. Bain ◽  
Jackie E. Kendrick ◽  
Anthony Lamur ◽  
Yan Lavallée ◽  
Eliza S. Calder ◽  
...  
Keyword(s):  
Apparent Viscosity ◽  
Eruption Style ◽  
Vulcanian Explosions ◽  
Plagioclase Microlite ◽  
Volcanic Conduit ◽  
Order Of Magnitude ◽  
Deformation Processes ◽  
Textural Data ◽  
The Relationship ◽  
Magma Rheology

Understanding the relationship between degassing, crystallization processes and eruption style is a central goal in volcanology, in particular how these processes modulate the magnitude and timing of cyclical Vulcanian explosions in intermediate magmas. To investigate the influence of variations in crystal micro-textures on magma rheology and eruption dynamics, we conducted high-temperature (940°C) uniaxial compression experiments at conditions simulating a shallow volcanic conduit setting on eight samples of high-crystallinity andesite with variable plagioclase microlite populations from the 2004 to 2010 Vulcanian explosions of Galeras volcano, Colombia. Experiments were conducted at different strain rates to measure the rate-dependence of apparent viscosities and assess the dominant deformation processes associated with shear. Variations in plagioclase micro-textures are associated with apparent viscosities spanning over one order of magnitude for a given strain rate. Samples with low numbers of large prismatic microlites behaved consistently with published rheological laws for crystalline dome samples, and displayed extensive micro-cracking. Samples with high numbers of small tabular microlites showed a lower apparent viscosity and were less shear-thinning. The data suggest a spectrum of rheological behavior controlled by concurrent variations in microlite number, size and shape. We use previously published micro-textural data for time-constrained samples to model the apparent viscosity of magma erupted during the 2004–2010 sequence of Vulcanian explosions and compare these results with observed SO2 fluxes. We propose that variations in magma decompression rate, which are known to produce systematic textural differences in the plagioclase microlite cargo, govern differences in magma rheology in the shallow conduit. These rheological differences are likely to affect the rate at which magma densifies as a result of outgassing, leading to magmatic plugs with a range of porosities and permeabilities. The existence of magmatic plugs with variable physical properties has important implications for the development of critical overpressure driving Vulcanian explosions, and thus for hazard assessment during volcanic crises. We suggest a new conceptual model to explain eruption style at andesitic volcanoes based on micro-textural and rheological differences between “plug-forming” and “dome-forming” magma. We advance that existing rheological laws describing the behavior of andesitic magma based on experiments on dome rocks are inappropriate for modeling large Vulcanian explosions (∼106 m3), as the magma involved in these eruptions lacks the characteristics required to form exogenous lava domes.

Rheology of ERF on Various Flow Fields

1999 ◽  
Vol 13 (14n16) ◽  
pp. 1886-1892
Author(s):  
Kunio Shimada ◽  
Shinichi Kamiyama ◽  
Toyohisa Fujita ◽  
Makio Iwabuchi ◽  
Hitoshi Nishida ◽  
...  
Keyword(s):  
Electric Field ◽  
Yield Stress ◽  
Apparent Viscosity ◽  
Volumetric Flow Rate ◽  
Rotating Disk ◽  
Electrorheological Fluid ◽  
Flow Fields ◽  
Hydrodynamic Characteristics ◽  
Concentric Cylinder ◽  
Electrorheological Effect

This paper is concerned with the experimental investigation of electrorheological effect (ER effect) on apparent viscosity and yield stress obtained from hydrodynamic characteristics of electrorheological fluid (ERF) in various flow fields. Our conducting flow fields are made by using rectangular duct, concentric cylindrical pipe, rotating disk and rotating concentric cylinder. The measured parameters of the former two cases are pressure difference at a given volumetric flow rate, and the latters are torque at a given angular velocity. Our using ERF is suspension type. We arrange these data to obtain increment of apparent viscosity and yield stress with and without a supplying D.C. electric field by using integral method of rheology. It is clarified that qualitative values of increment of apparent viscosity and yield stress are different at each flow field. In addition, the quantitative ER effects of shear rate and electric field strength on the increment of apparent viscosity and yield stress are clarified.

Controllable Squeeze Film Damper (An Application of Electro-Rheological Fluid)

1992 ◽  
Vol 114 (3) ◽  
pp. 354-357 ◽  
Author(s):  
Shin Morishita ◽  
Jun’ichi Mitsui
Keyword(s):  
Apparent Viscosity ◽  
Vibration Mode ◽  
Squeeze Film ◽  
Damping Capacity ◽  
Flexible Rotor ◽  
Rotor Vibration ◽  
Squeeze Film Damper ◽  
Rotating Speed ◽  
Wide Range ◽  
Er Fluid

A notable characteristic of electro-rheological (ER) fluid is the variation of its apparent viscosity with the application of an electric field. The application of this characteristic to the performance of squeeze film damper of a flexible rotor is investigated in this paper. It is shown experimentally that by controlling the supporting damping capacity continuously, rotor vibration can be reduced remarkably a wide range of rotating speed. Moreover, the study indicates experimentally that there exists an optimum supporting damping for every vibration mode.

Dissipative Heating Effects and End Corrections for Viscous Newtonian Flow in High Shear Capillary Tube Viscometry

1975 ◽  
Vol 97 (3) ◽  
pp. 472-478 ◽  
Author(s):  
J. Jakobson ◽  
W. O. Winer
Keyword(s):  
Shear Stress ◽  
Apparent Viscosity ◽  
Capillary Tube ◽  
Dissipative Heating ◽  
High Shear ◽  
Flow Curves ◽  
Heating Effects ◽  
Order Of Magnitude ◽  
End Corrections ◽  
Newtonian Behavior

The effect of dissipation heating on the apparent viscosity measured in capillary tube viscometry is described in this paper. Conditions of low Reynolds number and high shear are assumed. End corrections to the tube flow, found to be 3π/16 times the diameter of the tube, are incorporated. The flow curves show decreasing apparent viscosity when the shear stress increases. The configuration of the flow curves plotted in logarithmic presentation are found to be identical for fluids with Newtonian behavior. Convection is the predominant mechanism in removal of the heat in short capillary tube. The estimated upper bound for the shear stress obtainable in short length capillary tubes appears to be of the order of magnitude of 10 MPa limited primarily by the pressure drop associated with the constant end correction from the flat ended inlet and exit of the tube.

Sign in / Sign up

Export Citation Format

Share Document