scholarly journals SHEAR STRESS MEASUREMENTS AT THE SEA BOTTOM BY MEANS OF FERROFLUIDS

2018 ◽  
pp. 88
Author(s):  
Antonino Viviano ◽  
Laura M. Stancanelli ◽  
Rosaria E. Musumeci ◽  
Enrico Foti
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Measurement Technique ◽  
Fixed Bed ◽  
Optical Readout ◽  
Experimental Campaign ◽  
Sea Bottom ◽  
Sensor Configuration ◽  
Bed Roughness ◽  
The Magnetic Field

An innovative measurement technique is proposed for investigating shear stress at sandy bottoms. This technique is based on the adoption of a ferrofluidic sensor and of an optical readout strategy. An experimental campaign is carried out for evaluating its performance. Experiments differ for the ferrofluidic sensor configuration (difference in the magnetic field) and for the bottom configurations (fixed bed or sandy bed). Calibration of the ferrofluidic sensor for the range of the investigated hydraulic condition and of the controlling magnetic field is presented. The ferrofluidic technique is promising when applied at sandy bottoms, as neither adhesion processes between sand grains and ferrofluid or influence of impacts of grains on the measurement are observed. In particular, the preliminary measure performed indicated that the ferrofluidic sensor is capable of sensing the different bed roughness.

scholarly journals Principal Component Gradiometer technique for removal of spacecraft-generated disturbances from magnetic field data

2020 ◽  
Author(s):  
Ovidiu Dragoş Constantinescu ◽  
Hans-Ulrich Auster ◽  
Magda Delva ◽  
Olaf Hillenmaier ◽  
Werner Magnes ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Principal Component ◽  
Field Measurements ◽  
Magnetic Field Data ◽  
Service Oriented ◽  
Sensor Configuration ◽  
Time Required ◽  
First Time ◽  
The Magnetic Field

Abstract. In situ measurement of the magnetic field using space borne instruments requires either a magnetically clean platform and/or a very long boom for accommodating magnetometer sensors at a large distance from the spacecraft body. This significantly drives up the costs and time required to build a spacecraft. Here we present an alternative sensor configuration and an algorithm allowing for ulterior removal of the spacecraft generated disturbances from the magnetic field measurements, thus lessening the need for a magnetic cleanliness program and allowing for shorter boom length. The proposed algorithm is applied to the Service Oriented Spacecraft Magnetometer (SOSMAG) onboard the Korean geostationary satellite GeoKompsat-2A (GK2A) which uses for the first time a multi-sensor configuration for onboard data cleaning. The successful elimination of disturbances originating from several sources validates the proposed cleaning technique.

Cleaning magnetometer data using multi sensor configuration

2020 ◽  
Author(s):  
Dragos Constantinescu ◽  
Hans-Ulrich Auster ◽  
Magda Delva ◽  
Olaf Hillenmaier ◽  
Werner Magnes ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Measurements ◽  
Sensor Arrangement ◽  
Magnetometer Data ◽  
Service Oriented ◽  
Sensor Configuration ◽  
First Time ◽  
The Magnetic Field ◽  
Magnetic Cleanliness

<p>Measuring the in situ magnetic field using space borne instruments requires either a magnetically clean platform and/or a very long boom for accommodating magnetometers sensors at a large distance from the spacecraft body. This significantly drives up the costs and time for building the spacecraft. Here we present an alternative sensor configuration and an algorithm allowing for ulterior removing of the spacecraft generated disturbances from the magnetic field measurements, thus lessening the need for a magnetic cleanliness program.</p><p>The Service Oriented Spacecraft Magnetometer (SOSMAG) onboard the Korean Geostationary Satellite GEO-KOMPSAT-2A (GK-2A) uses for the first time a multi-sensor configuration for onboard data cleaning. To remove the AC disturbances, a combination of the measurements from sensors placed at different positions from the disturbance sources is processed onboard. Sensor biases due to daily temperature variations are also removed using the specific SOSMAG sensor arrangement. </p><p> </p>

Comparison of Affecting Factors on the Shear Stress Output of Cylinder-Typed MRF Clutch

2015 ◽  
Vol 1094 ◽  
pp. 453-457
Author(s):  
Hai Feng Ji ◽  
Chun Fu Gao ◽  
Xin Sheng He ◽  
Guang Zhang
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Affecting Factors ◽  
Bingham Model ◽  
Theoretical Derivation ◽  
Proportionality Constant ◽  
Magneto Rheological ◽  
The Relationship ◽  
The Magnetic Field ◽  
Main Influence

With the purpose of studying the main influence on the cylinder-typed magneto-rheological fluid (MRF) clutch, the relationship between the output of shear stress and its affecting factors is presented in this paper; through theoretical derivation from the Bingham Model and the cylinder-typed shear model, the stress born by the MRF in the clutch is analysed, and the affecting factors on the clutch is also simulated and verified through experiments. The study shows that as the magnetic field strengthens, the shear stress of the cylinder-typed MRF clutch grows linearly, with proportionality constant at 0.162; the increase of shear rate, relevant to the magnetic field strength, makes little difference to the torque output, with proportionality constant at 0.00026B. The results indicate that mechanical-electrical integration of clutch devices can be achieved through the control of magnetic field output of the electromagnet.

scholarly journals Analysis of Influence of Temperature on Magnetorheological Fluid and Transmission Performance

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Song Chen ◽  
Jin Huang ◽  
Kailin Jian ◽  
Jun Ding
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Rheological Properties ◽  
Temperature Stability ◽  
Transmission Performance ◽  
Mr Fluid ◽  
Influence Of Temperature ◽  
Study Results ◽  
Influence Of Temperature On ◽  
The Magnetic Field

Magnetorheological (MR) fluid shows different performances under different temperature, which causes so many problems like the reduction of rheological properties of MR fluid under a high temperature condition, the uncontrollability of shear stress, and even failure of transmission; on that basis, the influence of temperature on the performance of MR fluid and the cause of the rise in temperature of MR transmission device are analyzed in this paper; the shearing transmission performance of the MR transmission device under the effect of an external magnetic field and the influence of temperature on the shearing stress and transmission performance are analyzed. The study results indicate that temperature highly influences the viscosity of MR fluid, and the viscosity influences the shear stress of the MR fluid. The viscosity of MR fluid gradually declines when temperature rises from 100°C. Once the temperature exceeds 100°C, the viscosity would increase and the temperature stability would decline. Temperature obviously influences the characteristics of MR transmission, and particularly, highly influences the characteristics of MR transmission once being higher than 100°C. The chaining of the material in the magnetic field is influenced, which causes the reduction of the rheological properties, the uncontrollability of the shear stress, and even the failure of transmission.

3-D Modeling the Magnetic Field due to Ocean Tidal Flow O1

2013 ◽  
Vol 658 ◽  
pp. 471-474
Author(s):  
Yan Xu ◽  
Jun Xu ◽  
Wei Hua Zhu ◽  
Xia Feng ◽  
Hai Yan Xie
Keyword(s):  
Magnetic Field ◽  
Field Data ◽  
Tidal Flow ◽  
Ocean Water ◽  
Magnetic Field Data ◽  
Tidal Motion ◽  
The Earth ◽  
Sea Bottom ◽  
Tidal Constituents ◽  
The Magnetic Field

The tidal motion of the ocean water through the ambient magnetic field, generates secondary electric and magnetic field. The magnetic fields generated by the diurnal (O1) ocean flow can be clearly detected. We simulate the magnetic signals for tidal constituents –diurnal (O1) tides. The idea of exploiting tidal signals for EM studies of the Earth is not new, but so far it was used only for interpretation of inland and transoceanic magnetic field data due to O1. Emphasis in this work is made on a discussion of sea bottom electric field of the same origin.

EXPERIMENTAL STUDIES ON MAGNETORHEOLOGICAL MODEL SUSPENSIONS

2007 ◽  
Vol 21 (28n29) ◽  
pp. 4967-4973 ◽  
Author(s):  
ALEXANDRA-MARIA TRENDLER ◽  
HOLGER BÖSE
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Experimental Studies ◽  
Iron Particle ◽  
Solid Content ◽  
Oil Viscosity ◽  
Base Oil ◽  
Sedimentation Behavior ◽  
Mr Fluids ◽  
The Magnetic Field

Magnetorheological model suspensions with different contents of iron particles have been investigated. The results show an increase of the shear stress by increasing the magnetic field and the solid content, which was mathematically modelled. The influence of the solid content is approximately exponential without magnetic field and linear in strong magnetic fields. The effect of the temperature and of the base oil viscosity on the shear stress is negligible in the field but decisive without field. The sedimentation behavior also strongly depends on the iron particle content, where MR fluids with a higher concentration settle with a lower intensity due to the higher sediment height. The response time of the magnetorheological model suspensions could not be clearly determined, but it is less than 10 milliseconds.

Hiemenz Magnetic Flow of Power-Law Fluids

1974 ◽  
Vol 41 (3) ◽  
pp. 822-823 ◽  
Author(s):  
Dj. S. Djukic
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Field Strength ◽  
Power Law ◽  
Transverse Magnetic ◽  
Power Law Fluid ◽  
Plane Flow ◽  
Magnetic Flow ◽  
Power Law Fluids ◽  
The Magnetic Field

The Galerkin approximative technique is used to solve the problem of stagnation in plane flow, the so-called “Hiemenz flow”, of a non-Newtonian power-law fluid in presence of a constant transverse magnetic field. The influence of the magnetic field strength on the wall shear stress is analyzed.

scholarly journals Maximum-variance gradiometer technique for removal of spacecraft-generated disturbances from magnetic field data

2020 ◽  
Vol 9 (2) ◽  
pp. 451-469
Author(s):  
Ovidiu Dragoş Constantinescu ◽  
Hans-Ulrich Auster ◽  
Magda Delva ◽  
Olaf Hillenmaier ◽  
Werner Magnes ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Measurements ◽  
Magnetic Field Data ◽  
Maximum Variance ◽  
Service Oriented ◽  
Corrected Data ◽  
Sensor Configuration ◽  
Time Required ◽  
The Magnetic Field

Abstract. In situ measurement of the magnetic field using spaceborne instruments requires a magnetically clean platform and/or a very long boom for accommodating magnetometer sensors at a large distance from the spacecraft body. This significantly drives up the costs and the time required to build a spacecraft. Here we present an alternative sensor configuration and a technique allowing for removal of the spacecraft-generated AC disturbances from the magnetic field measurements, thus lessening the need for a magnetic cleanliness programme and allowing for shorter boom length. The final expression of the corrected data takes the form of a linear combination of the measurements from all sensors, allowing for simple onboard software implementation. The proposed technique is applied to the Service Oriented Spacecraft Magnetometer (SOSMAG) on board the Korean geostationary satellite GeoKompsat-2A (GK2A). In contrast to other missions where multi-sensor measurements were used to clean the data on the ground, the SOSMAG instrument performs the cleaning on board and transmits the corrected data in real time, as needed by space weather applications. The successful elimination of the AC disturbances originating from several sources validates the proposed cleaning technique.

Turbulent duct flows in a liquid metal magnetohydrodynamic power generator

2012 ◽  
Vol 713 ◽  
pp. 243-270 ◽  
Author(s):  
Hiromichi Kobayashi ◽  
Hiroki Shionoya ◽  
Yoshihiro Okuno
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Load Resistance ◽  
High Load ◽  
Magnetic Flux Density ◽  
Load Factor ◽  
Mean Velocity ◽  
Power Generator ◽  
Optimal Load ◽  
The Magnetic Field

AbstractWe numerically assess the influence of non-uniform magnetic flux density and connected load resistance on turbulent duct flows in a liquid metal magnetohydrodynamic (MHD) electrical power generator. When increasing the magnetic flux density (or Hartmann number), an M-shaped velocity profile develops in the plane perpendicular to the magnetic field; the maximum velocity in the sidewall layer of the M-shaped profile increases to maintain the flow rate. Under the conditions of a relaminarized flow, the turbulence structures align along the magnetic field and flow repeatedly like a von Kármán vortex sheet. At higher Hartmann numbers, the wall-shear stress in the sidewall layer increases and the sidewall jets transit to turbulence. The sidewall jets in the MHD turbulent duct flows have profiles similar to the non-MHD wall jets, i.e. a mean velocity profile with outer scaling, Reynolds shear stress with the opposite sign in a sidewall jet, and two maxima for the turbulent intensities in a sidewall jet. The Lorentz force suppresses the vortices of the secondary mean flow near the Hartmann layer for low Hartmann numbers, whereas the secondary vortices remain near the Hartmann layer for high Hartmann numbers. An optimal load resistance (or load factor) to obtain a maximum electrical efficiency exists, because the strong Lorentz force for a low load factor and unextracted eddy currents for a high load factor reduce efficiency. When the value of the load factor is changed, the profiles of mean velocity and r.m.s. for the optimal load factor produce almost the same profiles as the high load factor near the open-circuit condition.

YIELD STRESS IN FERROFLUIDS?

2007 ◽  
Vol 21 (28n29) ◽  
pp. 4806-4812 ◽  
Author(s):  
HAMID SHAHNAZIAN ◽  
STEFAN ODENBACH
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Field Strength ◽  
Yield Stress ◽  
Magnetic Field Strength ◽  
Theoretical Investigations ◽  
Field Dependent ◽  
Special Stress ◽  
Viscoelastic Effects ◽  
The Magnetic Field

Recent experimental as well as theoretical investigations have shown that the formation of structures of magnetic nanoparticles has significant influence on the behaviour of ferrofluids. The dependence of this structure formation on the magnetic field strength and shear stress applied to the fluid leads to strong changes of the viscosity and to the appearance of viscoelastic effects in the fluids. The actual approaches for a description of the effects vary in the basic modeling of the fluid and its behaviour. Some models base on microscopic assumptions, other model the fluid on a mesoscale and even macroscopic descriptions abstaining from microscopic assumptions have been suggested. A point in which the predictions of the models differ is the question of an appearance of a magnetic field dependent yield stress in ferrofluids. For investigations concerning the appearance and field dependence of a yield stress a special stress controlled rheometer for ferrofluids has been designed. The preliminary results presented here, show a dependence of the yield stress on magnetic field strength for different kind of ferrofluids and magnetorheological fluids.

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