Mathematical Modelling of Magneto-Hydrodynamic Dampers With Time-Varying Fluid Properties

2005 ◽  
Author(s):  
Mario F. Letelier ◽  
Dennis A. Siginer ◽  
Jean-Paul Rouliez ◽  
Omar F. Corral
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Yield Stress ◽  
Time History ◽  
Field Variation ◽  
Time Varying ◽  
Viscosity Change ◽  
Flow Equations ◽  
Fluid Properties ◽  
Analytical Tools

The fluid dynamics of dampers is investigated for the case where the damping fluid flows through passages in which a magnetic field is applied. This is a specific case of a new and promising field of applications that has emerged through the design of devices that take advantage of some properties of the so-called electrorheological fluids and magnetorheological fluids (ERF and MRF). These fluids are created when a base fluid is seed with very small dielectric or iron particles, so that it reacts to electric or magnetic fields by developing some non-Newtonian characteristics, most prominently a yield stress, viscosity change, and also viscoelasticity. These fluid properties can be controlled through control of the electric or magnetic fields’ strength. In this paper, a typical damping load is modeled and related to the required flow of a MRF inside the damper. To this end the fluid is modeled as a Bingham fluid with time-varying yield-stress. The analysis here developed makes it possible to determine the magnetic field variation necessary in order to achieve a specific displacement of the damper’s piston. The flow equations are analytically solved for any time-history of the dimensionless fluid’s yield-stress. Main results are some simplified relationships that correlate damping load and magnetic field time-variations. These results aim at providing analytical tools that may facilitate dampers’ design.

An Inverse Method for Material Characterization of Magnetorheological Dampers

2007 ◽  
Author(s):  
Mario F. Letelier ◽  
Dennis A. Siginer ◽  
Jean-Paul Rouliez ◽  
Omar F. Corral
Keyword(s):  
Magnetic Field ◽  
Yield Stress ◽  
Time History ◽  
Field Variation ◽  
Mr Fluid ◽  
Bingham Plastic ◽  
Damper Design ◽  
Analytical Tools ◽  
Constitutive Parameters

Flow of magnetorheological (MR) fluids in dampers is investigated. The MR fluid flows through narrow passages in the damper subject to a magnetic field applied across the passages. The inverse problem of the determination of the required constitutive properties of the MR fluid together with the corresponding flow pattern for the efficient damping of a given load is solved. The fluid is modeled as a Bingham plastic with time-varying yield-stress. Flow is governed by the continuously adjustable constitutive parameters of the MR fluid which are determined to generate variable resistance to flow to dampen the selected load efficiently. The method developed leads to the determination of the magnetic field variation necessary to achieve a specific displacement of the piston in the damper. The governing equations are solved for any time history of the dimensionless yield stress of the fluid. Relationships that correlate damping load and magnetic field time variations are obtained. The analytical tools developed are helpful in damper design.

A New Approach to the Modeling of Magnetorheological Dampers and Application to Resonance Control

2021 ◽  
Author(s):  
Dennis A. Siginer ◽  
Mario Letelier ◽  
Juan Sebastián Stockle Henríquez
Keyword(s):  
Flow Pattern ◽  
Yield Stress ◽  
A Priori ◽  
Time History ◽  
Magnetorheological Damper ◽  
Mr Fluid ◽  
Variable Resistance ◽  
History Of ◽  
Displacement Pattern ◽  
Analytical Tools

Abstract A predetermined flow pattern in a magnetorheological damper providing continuously variable resistance to flow is required for efficient damping of a given load. The required predetermined flow pattern rests on the a priori determination of the constitutive properties of the magnetorheological (MR) fluid determined to generate variable resistance to flow. The inverse problem of constructing the predetermined response of the damper with a specific displacement pattern of the piston in the damper for efficient damping of a given load is solved. The magnetorheological (MR) fluid in the damper is modeled as a Bingham phase change material with time dependent yield stress offering continuously variable resistance to the flow in the piston to achieve the required specific displacement pattern. The governing equations are solved for any time history of the dimensionless yield stress of the fluid which in turn is determined from the imposed response of the damper. Analytical tools developed can be used in optimizing damper performance. The application of the method to resonance mitigation is illustrated.

Internal Organizational Measurement for Control of Magnetorheological Fluid Properties

2006 ◽  
Vol 129 (4) ◽  
pp. 423-428 ◽  
Author(s):  
John R. Lloyd ◽  
Miquel O. Hayesmichel ◽  
Clark J. Radcliffe
Keyword(s):  
Magnetic Field ◽  
Physical Properties ◽  
High Sensitivity ◽  
Time Varying ◽  
Measurable Effect ◽  
Mr Fluid ◽  
Fluid State ◽  
Mr Fluids ◽  
Fluid Properties ◽  
Field Excitation

Magnetorheological (MR) fluids change their physical properties when subjected to a magnetic field. As this change occurs, the specific values of the physical properties are a function of the fluid’s time-varying organization state. This results in a nonlinear, hysteretic, time-varying fluid property response to direct magnetic field excitation. Permeability, resistivity and permittivity changes of MR fluid were investigated and their suitability to indicate the organizational state of the fluid, and thus other transport properties, was determined. High sensitivity of permittivity and resistivity to particle organization and applied field was studied experimentally. The measurable effect of these material properties can be used to implement an MR fluid state sensor.

scholarly journals EM Site A.C. Magnetic Field Sources, Surveys and Solutions Part IV: Survey Data Analysis

1996 ◽  
Vol 4 (4) ◽  
pp. 20-21
Author(s):  
Curt Dunnam
Keyword(s):  
Magnetic Field ◽  
Data Analysis ◽  
Magnetic Fields ◽  
Survey Data ◽  
Field Survey ◽  
Survey Methods ◽  
Time Varying ◽  
Measured Field ◽  
The Magnetic Field ◽  
Analyze Data

Up to the present waypoint in this series on EM site magnetic fields, we have identified typical sources of time-varying magnetic field intensities, examined salient field characteristics and illustrated correct survey methods. Our goal this month is to analyze data collected at a proposed site and answer the key question of whether or not the candidate site is, as far as magnetic fields go, acceptable for EM use. In the process of analyzing the magnetic field survey data we will define some of the interpretive techniques involved and observe the distinction between localized (a.c. power) and non-localized (geomagnetic) time-varying fields. Finally, we will discuss the implications of EM susceptibility threshold vs. measured field ratios when considering remedial site shielding.

On the spontaneous magnetic field in a conducting liquid in turbulent motion

1950 ◽  
Vol 201 (1066) ◽  
pp. 405-416 ◽  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Energy ◽  
Turbulent Motion ◽  
Small Scale ◽  
Flow Equations ◽  
Metallic Conductor ◽  
Set Up ◽  
The Stability ◽  
The Magnetic Field

Several recent investigations in geophysics and astrophysics have involved a consideration of the hydrodynamics of a fluid which is a good electrical conductor. In this paper one of the problems which seem likely to arise in such investigations is discussed. The fluid is assumed to be incompressible and in homogeneous turbulent motion, and externally imposed electric and magnetic fields are assumed to be absent. The equations governing the interaction of the electromagnetic field and the turbulent motion are set up with the same assumptions as are used to obtain the Maxwell and current flow equations for a metallic conductor. It is shown that the equation for the magnetic field is identical in form with that for the vorticity in a non-conducting fluid; immediate deductions are that lines of magnetic force move with the fluid when the conductivity is infinite, and that the small-scale components of the turbulence have the more powerful effect on the magnetic field. The first question considered is the stability of a purely hydrodynamical system to small disturbing magnetic fields, and it is shown that the magnetic energy of the disturbance will increase provided the conductivity is greater than a critical value determined by the viscosity of the fluid. The rate of growth of magnetic energy is approximately exponential, with a doubling time which can be simply related to the properties of the turbulence. General mechanical considerations suggest that a steady state is reached when the magnetic field has as much energy as is contained in the small-scale components of the turbulence. Estimates of this amount of energy and of the region of the spectrum in which it will lie are given in terms of observable properties of the turbulence.

Time-varying magnetic fields increase cytosolic free Ca2+ in HL-60 cells

1990 ◽  
Vol 259 (4) ◽  
pp. C687-C692 ◽  
Author(s):  
J. J. Carson ◽  
F. S. Prato ◽  
D. J. Drost ◽  
L. D. Diesbourg ◽  
S. J. Dixon
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Electromagnetic Fields ◽  
Biological Effects ◽  
Static Field ◽  
Free Calcium ◽  
Time Varying ◽  
Parallel Control ◽  
Magnetic Resonance Imaging Mri ◽  
Radiofrequency Electromagnetic Field

Electromagnetic fields have been reported to cause a variety of biological effects. It has been hypothesized that many of these phenomena are mediated by a primary effect on the concentration of cytosolic free calcium ([Ca2+]i). We investigated the effects of exposure to electromagnetic fields on [Ca2+]i in HL-60 cells using the Ca2(+)-sensitive fluorescent indicator indo-1. Indo-1-loaded cell samples were exposed to a radiofrequency electromagnetic field, a static magnetic field, and a time-varying magnetic field, which were generated by a magnetic resonance imaging (MRI) unit. We found that a 23-min exposure to all three fields, in combination, induced a significant increase in [Ca2+]i of 31 +/- 8 (SE) nM (P less than 0.01, n = 13) from a basal level of 121 +/- 8 nM. Also, cells exposed to only the time-varying magnetic field had a mean [Ca2+]i that was 34 +/- 10 nM (P less than 0.01, n = 11) higher than parallel control samples. Separate exposure to the radio-frequency (6.25 MHz) or static field (0.15 T) had no detectable effects. These results demonstrate that time-varying magnetic fields alter [Ca2+]i and suggest that at least some of the reported biological effects of time-varying magnetic fields may arise from elevation of [Ca2+]i.

Nature-inspired position determination using inherent magnetic fields

TECHNOLOGY ◽  
2014 ◽  
Vol 02 (02) ◽  
pp. 161-170 ◽  
Author(s):  
Saber Taghvaeeyan ◽  
Rajesh Rajamani
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Measurement System ◽  
Internal Combustion Engines ◽  
Magnetic Sensor ◽  
Field Variation ◽  
Position Measurement ◽  
Hydraulic Cylinders ◽  
Accurate Position ◽  
Field Lines

Many creatures in nature, including butterflies, newts, and mole rats, use the Earth's inherent magnetic field for navigation. They use magnetic field lines and variations in field intensity to determine their geographical position. This paper seeks to apply similar techniques to measure the positions of individual ferromagnetic objects found all around us in everyday life. Ferromagnetic objects have inherent magnetic fields around them. We show here that the magnetic field variation around a ferromagnetic object can be modeled using purely the geometry of the object under consideration. By exploiting this model, the position of the object can be measured quite accurately using a small inexpensive magnetic sensor. Further, the use of just one additional redundant magnetic sensor can eliminate the need to calibrate the position measurement system. As demonstrated in the paper through a series of experimental results, the developed measurement system is applicable to accurate position measurement of small and large ferromagnetic objects, including cars on highways, oscillating pistons in internal combustion engines, pneumatic cylinders, hydraulic cylinders, as well as moving parts in many machines.

scholarly journals <i>Brief communication</i> "Modeling tornado dynamics and the generation of infrasound, electric and magnetic fields"

2010 ◽  
Vol 10 (2) ◽  
pp. 295-298 ◽  
Author(s):  
E. D. Schmitter
Keyword(s):  
Magnetic Field ◽  
Velocity Field ◽  
Magnetic Fields ◽  
Early Warning ◽  
Time Varying ◽  
Dust Devils ◽  
Model Calculations ◽  
Electric And Magnetic Fields ◽  
Electric And Magnetic Field ◽  
Insight Into

Abstract. Recent observations endorse earlier measurements of time varying electric and magnetic fields generated by tornadoes and dust devils. These signals may provide a means for early warning but together with a proper modeling approach can also provide insight into geometry and dynamics of the vortices. Our model calculations show the existence of pressure resonances characterized as acoustic duct modes with well defined frequencies. These resonances not only generate infrasound but also modulate the charge density and the velocity field and in this way lead to electric and magnetic field oscillations in the 0.5–20-Hz range that can be monitored from a distance of several kilometers.

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