NUMERICAL STUDY OF THE RESPONSE TIME OF ER SUSPENSIONS

1996 ◽  
Vol 10 (23n24) ◽  
pp. 3037-3044 ◽  
Author(s):  
JUN-ICHI TAKIMOTO ◽  
KEIJI MINAGAWA ◽  
KIYOHITO KOYAMA
Keyword(s):  
Growth Rate ◽  
Steady State ◽  
Shear Rate ◽  
Field Strength ◽  
Electric Field ◽  
Particle Density ◽  
Numerical Study ◽  
Dispersed Particles ◽  
Induced Stress ◽  
Steady Shear Flow

Transient response of model ER suspensions to step-wise electric field under steady shear flow is studied by numerical simulations. The electrically induced stress increases almost linearly with time up to the steady-state value, and this increase directly reflects the growth of the chain-like clusters of the dispersed particles. As the shear rate increases, the response becomes faster since the growth rate of the clusters increases and the steady-state length of the clusters decreases. The response also becomes faster by increasing the particle density or electric field, but the dependence on the field strength is rather weak.

HYDRODYNAMIC CHARACTERISTICS OF ELECTRORHEOLOGICAL FLUID IN A PARALLEL DUCT FLOW

2001 ◽  
Vol 15 (06n07) ◽  
pp. 980-987
Author(s):  
K. SHIMADA ◽  
S. KAMIYAMA
Keyword(s):  
Shear Rate ◽  
Friction Coefficient ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Apparent Viscosity ◽  
Wall Friction ◽  
Hydrodynamic Characteristics ◽  
Duct Flow ◽  
Newtonian Viscosity

An experimental investigation is conducted to clarify the hydrodynamic characteristics of ERF with elastic particles of smectite in a two-dimensional parallel duct of various widths. Experimental data on pressure difference to a volumetric flow rate in a supplying D.C. electric field are measured. These data are arranged to obtain the apparent viscosit by using the integral method of rheology. From the data of apparent viscosity, the wall friction coefficient is obtained. The increment of the apparent viscosity caused by the applying electric field is a function of shear rate as well as the electric field strength and the width of the duct. However, the wall friction coefficient is not a function of elecric field strength and the width of the parallel duct, but only of shear rate. The yield stress is a function of the width of the parallel duct as well as of electric field strength. The ratio of Non-Newtonian viscosity in the apparent viscosity is varied by the intensity of the shear rate.

DIFFERENCES IN STEADY CHARACTERISTICS AND RESPONSE TIME OF ERF ON ROTATIONAL FLOW BETWEEN ROTATING DISK AND CONCENTRIC CYLINDER

2001 ◽  
Vol 15 (06n07) ◽  
pp. 1050-1056 ◽  
Author(s):  
K. SHIMADA ◽  
H. NISHIDA ◽  
T. FUJITA
Keyword(s):  
Shear Rate ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Current Density ◽  
Rotating Disk ◽  
Settling Time ◽  
Rotational Flow ◽  
Concentric Cylinder ◽  
Constant Shear Rate

We made an experimental investigation of the steady characteristics of torque, current density, and response time of ERF on rotational flow of the disk and the concentric cylinder. We used smectite particles suspension ERF and D.C. electric field. We compared the steady shearstress, current density, and the rise and settling time of the concentric cylinder and with those of the rotating disk. Then we clarified the differences. At a larger electric field strength, the shear stress, yield stress, and apparent viscosity to a constant shear rate in the case of the rotating disk are larger than they are in the case of the rotating concentric cylinder. However, at a larger electric field strength, the current density to a constant shear rate in the case of the rotating disk is smaller than it is in the case of the rotating concentric cylinder. Rise time of torque in the case of the rotating disk is faster than it is in the case of the rotating concentric cylinder. However, rise time of current density in the case of the rotating disk is slower than it is in the case of the rotating concentric cylinder at a small electric field strength. On the other hand, the difference of settling time of torque and current density between the rotating disk and the rotating concentric cylinder is changed by the electric field strength and shear rate. The settling time of torque in the case of the rotating disk is faster than it is in the case of the rotating concentric cylinder at a large electric field strength and large shear rate. The settling time of current density in the case of the rotating disk is slower than it is in the case of rotating concentric cylinder at a small electric field strength. Based on these results, the rotating disk has an efficiency of obtained torque to given electric power greater than that of the rotating concentric cylinder.

scholarly journals Ladungsträgerverluste in einem schwachionisierten stationären Gleichstromplasma im toroidalen Magnetfeld

1967 ◽  
Vol 22 (7) ◽  
pp. 1039-1057
Author(s):  
F. Karger
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Particle Density ◽  
Linear Part ◽  
Longitudinal Electric Field ◽  
Theoretical Limit ◽  
Critical Magnetic Fields ◽  
Weakly Ionized

For the particle losses of a weakly ionized plasma which result from the torus drift in a curved magnetic field, an expression is derived which is valid for certain parameters of the positive column of a gas discharge. To check this theory the “AMBIPOL” device was built. With this device it was possible to determine simultaneously the losses both in the toroidal and in the linear magnetic field by measuring the longitudinal electric field strength. As theory predicts, with growing magnetic field strength a weaker decrease of the longitudinal electric field was observed in the toroidal part of the discharge as compared to the linear part. The measured values of the relative electric field strength, however, exceed the theoretical limit, although the measurements of the electric field in the straight part and the measurements of the particle density and of the electron temperature in the curved part are consistent with theory. Moreover, contrary to the expectations, the onset of the KADOMTSEV instability occurs at lower critical magnetic fields in the toroidal part than in the straight part. Several possible explanations are discussed. In a later paper it will be attempted to make a choice among the three most probable ones.

HYSTERESIS PHENOMENON IN FLOW-CURVES OF ER FLUIDS CONTAINING SULFONATED POLYMER PARTICLES

2001 ◽  
Vol 15 (06n07) ◽  
pp. 1070-1077 ◽  
Author(s):  
RYUJI AIZAWA ◽  
SHEILA L. VIEIRA ◽  
MASAMI NAKANO ◽  
YOSHINOBU ASAKO
Keyword(s):  
Shear Rate ◽  
Electric Field ◽  
Volume Fraction ◽  
Hysteresis Phenomenon ◽  
Polymer Particles ◽  
Concentric Cylinder ◽  
Flow Curves ◽  
Shear Rates ◽  
Dispersed Particles ◽  
Er Fluids

The ER fluids containing sulfonated polymer particles were continuously sheared at increasing and decreasing shear rates using a rotary concentric cylinder rheometer and the hysteresis in the up- and down-flow-curves were analyzed. The ER fluids show hysteresis of shear stress and current density. The up-curve (when shear rate increased) was located below the down-curve (when shear rate decreased). As the electric field increased, the area in the hysteresis curves increased. The hysteresis depended on the electric field strength, the time of the applied electric field, the volume fraction of particles and the water content of the particles. Hysteresis phenomenon was explained, based on the formation of agglomerations of dispersed particles in the ER fluid and on changes of the lamellar formations

TRANSIENT BEHAVIOR OF THE MICROSTRUCTURE OF ELECTRORHEOLOGICAL FLUIDS IN SHEAR FLOW MODE

2001 ◽  
Vol 15 (06n07) ◽  
pp. 695-703 ◽  
Author(s):  
S. L. VIEIRA ◽  
M. NAKANO ◽  
S. HENLEY ◽  
F. E. FILISKO ◽  
L. B. POMPEO NETO ◽  
...  
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Shear Flow ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Transient Behavior ◽  
Electrorheological Fluids ◽  
Flow Mode ◽  
Er Fluid

It was reported that under the simultaneous stimulus of an electric field and shear, the particles in an ER fluid form lamellar formations in the direction of shear (adhered to one of the electrodes) which may be responsible for the ER activity more than the strength of the chains. In this way, it would be expected that the shear stress should change consistently with the morphology of the formations. In this work we studied the effect of shearing time, electric field strength and shear rate on the shear stress. We suggest that changes on shear stress with time are due to changes of the morphology of the lamellar formations.

Terahertz Electroluminescence of 6H-SiC Natural SiC Superlattice in Bloch Oscillations Regime

2012 ◽  
Vol 717-720 ◽  
pp. 553-556 ◽  
Author(s):  
Vladimir Ilich Sankin ◽  
Alexander V. Andrianov ◽  
A.G. Petrov ◽  
P.P. Shkrebiy ◽  
A.O. Zacharin
Keyword(s):  
Steady State ◽  
Field Strength ◽  
Electric Field ◽  
Emission Spectrum ◽  
Liquid Helium ◽  
Linear Dependence ◽  
Bloch Oscillations ◽  
Terahertz Emission ◽  
Natural Superlattice ◽  
Characteristic Field

We report on efficient terahertz emission in the region of 1.5-2 THz from high electric field biased 6H-SiC structures with a natural superlattice at liquid helium temperatures. The shape of the emission spectrum, the linear dependence of its maximum on the bias and the characteristic field strength required to achieve the emission allow the emission to be attributed to steady-state Bloch oscillations of electrons in the SiC natural superlattice.

Fundamentals of Particle Flocculation and Removal From Water

1994 ◽  
Vol 344 ◽  
Author(s):  
Patrick T. Spicer ◽  
Sotiris E. Pratsinis
Keyword(s):  
Growth Rate ◽  
Steady State ◽  
Shear Rate ◽  
Aluminum Sulfate ◽  
Stirred Tank ◽  
Turbulent Shear ◽  
Size Distributions ◽  
Floc Size ◽  
Shear Rates ◽  
State Size

AbstractThe flocculation of polystyrene particles with aluminum sulfate or alum (Al2 (SO4)3) by turbulent shear was studied as a function of the applied shear rates (63–129 s−1) and flocculant concentrations (11 and 32 mg/L) in a stirred tank. Increasing the shear rate increased the floc growth rate but decreased the maximum attainable floc size. Increasing the concentration of alum increased the floc growth rate and the maximum floc size. A steady state between floc growth and breakage was attained after which the floc size distribution no longer changed. The normalized steady state size distributions allowed evaluation of the relative contributions of shear rate and flocculant concentration to the performance of the process.

High field kinetic processes in anodic oxide films on aluminium. I. Current transients for linearly changing electric field strength

1968 ◽  
Vol 46 (4) ◽  
pp. 535-548 ◽  
Author(s):  
M. J. Dlgnam ◽  
P. J. Ryan
Keyword(s):  
Steady State ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
High Field ◽  
Oxide Films ◽  
Anodic Oxide ◽  
Anodic Oxide Films ◽  
Differential Field ◽  
Field Coefficient

Anodic oxide films were formed on high purity aluminium (99.996 %) under steady-state conditions (current and field strength constant) in a glycol–borate electrolyte until the film reached a predetermined thickness at which point the anodic overpotential was changed rapidly and in a linear manner. As little film growth occurred during these linear sweeps, the conditions corresponded to linearly changing field strength. From these data, the transient differential field coefficient, β1, defined by[Formula: see text]where i and E are the ion current density and electric field strength and Es the steady-state formation field strength, was determined β1 was found to vary linearly with Es in the manner [Formula: see text] with [Formula: see text] A recent theory proposed by one of us (M. J. D.) predicts that the parameter [Formula: see text] should have the same value as that deduced from the field dependence of the steady-state differential field coefficient,[Formula: see text]Such agreement was indeed found, two independently determined 'steady-state' values of [Formula: see text] being 3.53 ± 11% and 3.11 ± 14% ÅV−1. A direct comparison of the present results with previous steady-state results gave βs/β1 = μs/μ1 = 3.09. More complex features of the transients were also found to be in accord with the above theory, but could be accounted for almost as well by an earlier theory, the so-called high field Frenkel defect theory.Dielectric constant values determined from the current discontinuity appearing upon application of the linearly increasing field gave K1 = 8.35 ± .1 for transients commencing from steady-state conditions and K1 = 8.85 ± .2 for films formed then 'aged' at E = 0 before measurement. Certain anomalies with regard to the charging current were apparent.

Enhancement of Heat Transfer by an Electric Field for a Drop Translating at Intermediate Reynolds Number

2005 ◽  
Vol 127 (10) ◽  
pp. 1087-1095 ◽  
Author(s):  
Rajkumar Subramanian ◽  
M. A. Jog
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Steady State ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Continuous Phase ◽  
Dispersed Phase ◽  
Enhancement Of Heat Transfer

The enhancement of heat transfer by an electric field to a spherical droplet translating at intermediate Reynolds number is numerically investigated using a finite volume method. Two heat transfer limits are considered. The first limit is the external problem where the bulk of the resistance is assumed to be in the continuous phase. Results show that the external Nusselt number significantly increases with electric field strength at all Reynolds numbers. Also, the drag coefficient increases with electric field strength. The enhancement in heat transfer is higher with lower ratio of viscosity of the dispersed phase to the viscosity of the continuous phase. The second heat transfer limit is the internal problem where the bulk of the resistance is assumed to be in the dispersed phase. Results show that the steady state Nusselt number for a combined electrically induced and translational flow is substantially greater than that for purely translational flow. Furthermore, for a drop moving at intermediate Reynolds number, the maximum steady state Nusselt number for a combined electrically induced and translational flow is slightly greater than that for a purely electric field driven motion in a suspended drop.

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