Electromagnetic Flowmeter Research Articles

On the Spatial Response of Electromagnetic Flowmeters

This paper investigates the spatial response of electromagnetic flowmeters, which are commonly used to measure bulk flow in various industrial applications. While most flowmeters focus on measuring the overall flow rate, this paper explores the response of a flowmeter to the spatial distribution of the flow and develops a new dipole form of the forward map. By writing the Neumann Green’s function and using the dipole form, we investigate reconstruction of the distribution of flow within the pipe. The paper presents examples of flow tomography using a truncated singular value reconstruction, which enables accurate visualization of the flow field. By examining the spatial response of electromagnetic flowmeters and presenting a new dipole form of the forward map, this paper contributes to the ongoing effort to improve the accuracy and informativeness of flow measurements in industrial settings.

Optimization of electromagnetic flow measurement system based on a new mesh electrode

Electromagnetic flowmeter(EMF) is a common volumetric flow measurement instrument widely used in industrial flow measurement. With the development of EMF in the direction of high precision and intelligence, it is increasingly urgent to further improve the accuracy of EMF measurement. The key to reducing measurement error and eliminating the impact of interference noise is optimizing the electromagnetic flow sensor structure. Aiming at the existing EMF electrode optimization deficiencies, a new mesh structure electrode is firstly proposed in this paper. Then, a theoretical study on the distribution of virtual current density based on this mesh structure electrode is carried out, different structure electrodes are verified and analyzed through COMSOL finite element simulation, and the optimal structure design parameters of the new mesh electrode are obtained. Finally, an experimental platform is built, and a comparative experiment is conducted on the electromagnetic flow measurement system composed of the new mesh structure electrodes. The experimental results show that the maximum relative error of the optimized electromagnetic flow measurement system (OEMFS) is reduced by 0.47% compared with the ordinary EMF in the non-axisymmetric flow test. In the low-flow velocity test, the maximum relative error of the OEMFS is reduced by 7.46% compared with the ordinary EMF. In the strong interference test, the steady-state fluctuation of the amplitude of the OEMFS is reduced by 5.01% compared with the ordinary EMF. The OEMFS has better anti-interference, and the relative error of the system is less affected by the change in flow rate.

Case Study: Addressing the Mounting Challenge of Produced-Water Metering Inaccuracy With Nanotechnology

_ As the energy industry strives to reuse produced water and disposal costs of produced water increase, it has elevated the need for more accurate measurement to save money. Measurement of produced water in the US unconventional market is impacted by paraffin deposition on the meters causing inaccurate readings of the volume of produced water. The industry is starting to address this growing issue by applying new technology solutions that enable lasting accuracy in the place of routine maintenance that provides a temporary solution. Most oil and gas producers face paraffin buildup on the inside surface of their electromagnetic flowmeters. These meters are typically located on the produced-water leg, downstream of production and test separators. Paraffin, a waxy substance present in crude oil production, drops out of solution as the fluid cools from the wellhead through the surface equipment. How Paraffin Impacts Metering As the fluid is transported through the pipes, it cools down, causing the paraffin to solidify and deposit on the walls of pipes and flowmeters. Separators that are designed to remove most of the paraffin via heat are still susceptible to the accumulation of small amounts of paraffin that may coat the pipe and measurement devices. Electromagnetic flowmeters are used to measure the volumetric flow rate of conductive fluids in pipelines, such as produced water. They operate by generating a magnetic field across the flow path and measure the voltage induced by the fluid as it flows through the magnetic field. The voltage is proportional to the flow velocity and the magnetic field strength, which is used to calculate the volumetric flow rate of the fluid. Electromagnetic flowmeters contain a minimum of two electrodes, composed of ceramic or metallic materials depending upon the manufacturer. The electrodes read the induced voltage of the produced water flowing through the meter. An insulating liner is placed inside the meter between the conductive fluid and the metal body. This isolates the fluid being measured from the meter body, preventing the fluid from creating an electrical short circuit. Paraffin buildup affects the accuracy and reliability of electromagnetic flowmeters as it nucleates on the electrodes and the liner of the meter. Over time, the paraffin deposition will increase around the electrodes, essentially insulating the electrodes from the fluid. At this point the conductivity of the fluid is artificially reduced, and the flowmeter will under read. If the paraffin coating on the electrodes becomes thick enough, a flowmeter will be completely insulated from the produced water, which the meter interprets as zero flow. As the paraffin coating on the liner increases, the cross-sectional area of the meter is reduced, creating a higher fluid velocity which results in the meter overreading the flowrate (Q = Av where A is the cross-sectional area of flow and v is its average velocity).

Study on the Static and Dynamic Characteristics of Vortex Electric Field in Electromagnetic Flowmeter and its Role in Attenuating Slurry Noise

Study on the Static and Dynamic Characteristics of Vortex Electric Field in Electromagnetic Flowmeter and its Role in Attenuating Slurry Noise

Sonic velocity measurement in molten Pb–Li (16) at high temperature for ultrasonic flowmeter applications

An ultrasonic flowmeter can be a good alternate to electromagnetic flowmeter, being used extensively for high temperature liquid metals. It has an advantage of using it at any location and at any point of time. However, the usage of ultrasonic techniques in high temperature liquid metals is not well established, especially in molten Pb–Li. Pb–Li is considered as a potential coolant candidate in fusion reactor. To study the applicability of ultrasonic techniques in Pb–Li medium with a future scope to develop an ultrasonic flowmeter, a high temperature experimental facility was developed. Sonic velocity was measured in Pb–Li at temperatures ranging from 285 °C to 375 °C using the pulse echo method. It was observed that ultrasonic waves get highly attenuated in molten Pb–Li medium. Out of various tested ways, introduction of W reflector plate could provide detectable reflected signal. The proof of principle test was carried out on few liquids with known values of sonic velocity. The measured sonic velocities have a deviation of ∼6% from that of the reported values.

Abstract 10890: A Simplified Method for Correction of Effective Regurgitant Orifice and Flow Underestimation by Pisa in Non-Circular Orifices: An in vitro Study

Introduction: The proximal isovelocity surface area (PISA) method has been validated for quantifying severity of mitral regurgitation (MR) in orifices with circular geometry. However, functional MR often has an elliptical orifice, which alters the proximal isovelocity contour from a hemisphere to a hemi-ellipsoid. Studies have previously shown that PISA underestimates regurgitant flow (RF) and effective regurgitant orifice (ERO) in functional MR. Hypothesis: The application of a simplified hemi-ellipsoid formula based on biplane color Doppler improves accuracy in calculating RF and ERO across elliptical orifices. Methods: An in vitro model for flow quantification was used for all experiments. Multiple size orifices with minor to major ratios ranging from 1:1 to 1:9 were constructed by 3D printing. Flow was adjusted at multiple intervals to generate peak flow velocities ranging from 4.1 to 5.5 m/s and aliasing velocities from 12 to 18 cm/s. Isovelocity contours were evaluated by biplane color Doppler (Figure 1A). RF and ERO were estimated using the traditional hemispheric PISA (HS-PISA) formula and a simplified hemiellipsoid formula (HE-PISA) based on two orthogonal diameter measurements (Figure 1A and 1B). The estimated RF and ERO values were compared and validated against those derived from a magnetic flowmeter (FM). Results: Isovelocity contours changed from hemisphere to hemi-ellipsoid orifices with increasing ellipticity ratios. HS-PISA significantly underestimated RF (116 ± 27 vs FM 155 ± 20 ml/s) and ERO (26 ± 4 vs FM 34 ± 1 mm 2 ). Underestimation was significantly reduced by HE-PISA (135 ± 17 ml/s and 30 ± 2.5 mm 2 , both p<0.001). Conclusions: A simplified hemi-ellipsoid PISA method provides more accurate assessment of RF and ERO in regurgitant orifices with non-circular geometries.

Empirical roughness coefficients for moderate floods in an open conduit cave: Fullers stream canyon, Culverson Creek Cave System, West Virginia

Open conduit modeling of cave stream floods can yield useful information about water velocities and shear stresses, which can in turn be used to estimate sediment transport capabilities. All such calculations require roughness coefficients for estimating energy losses and a priori knowledge of either discharge or flow depths to set model boundary conditions. However, the difficulties associated with observing in-cave floods generally preclude measuring discharge; roughness coefficients must be assumed based on channel properties. To overcome these challenges, we monitored stream flow depths in Fullers Cave, Greenbrier County, West Virginia using pressure transducers, and simultaneously measured stage and discharge in a karst window immediately upstream of the cave. Five pressure transducers were deployed opportunistically along a 93-meter-long reach in a 10+ meter high canyon averaging 1.5 to 3 meters wide. Stage-discharge relationships were determined for the karst window using an electromagnetic flow meter for floods with peak discharges of 1.66 m3 s-1 or less. The collected data was used to obtain the empirical Manning’s n roughness values, head losses, and energy gradients. Calculated floodwater velocities are comparable to values obtained from scallops on passage walls. Major energy losses were observed where breakdown partially occludes the passage. At peak flow, Manning n values average 0.053 for reaches typified as cobble-floored canyons, but n was 0.069 in the breakdown reach. Roughness values declined exponentially with increasing discharge, but friction slopes calculated using head losses show more complex relationships with discharge. Notably, n values back calculated using bed gradients differ from those calculated using measured head losses by as little as 12%, so the use of bed gradients in roughness estimations will generally yield reasonable approximations of flow conditions. Fullers Cave experiences significantly larger open conduit floods than we observed, so additional work is needed to estimate roughness coefficients for higher discharges. Our empirical roughness coefficients can be applied to similar cave passages in other caves and contexts, including modeling slot canyon-like channels, and our methods demonstrate a technique for measuring hard to obtain data. The addition of data for open conduit conduits significantly expands the range of environments that can be modeled using empirical data beyond pipe-full caves. Applications include studying flooding, sediment transport, and bedrock erosion process. All of these topics will be addressed in Fullers in the future.

INV-FLOW: New Possibilities to Evaluate the Technical Condition and Function of Extraction Wells

The declining supply of available groundwater resources is increasing the importance of extraction wells. To maximize the yield of extraction wells, the operators do not always respect the sustainable use of groundwater resources. These efforts can affect water quality and impact the service life of an extraction well, mainly through the clogging process. As part of the INV-FLOW project, an apparatus for evaluating the functionality of an extraction well by measuring the vertical water flow through its screen and filter was designed and tested. The apparatus consists of two electromagnetic induction flowmeters, two pneumatic seals, and a pump with the possibility of regulation. After an initial laboratory verification of the fundamental concept, the apparatus was successfully tested in real conditions. Two extraction wells, HJ-3 and HJ-4, intended for water supply to an agricultural production plant, were measured at a pilot site in the Czech Republic using the INV-FLOW apparatus. Although the HJ-3 extraction well is at the end of its service life, the HJ-4 extraction well is a newly installed well. In the new extraction well, HJ-4, a high proportion of water flowing through the gravel pack relative to the total pumping flow (93–97%) was measured using the INV-FLOW apparatus at different pumping rates. In the case of the HJ-3 extraction well, screen and filter clogging contributed significantly to the limited water flow through the gravel pack. In the most affected parts of the extraction well (15–20 m b.g.l.), the proportion of water flowing through the gravel pack relative to the total pumping flow ranged from 10 to 20%. The pilot tests confirmed the functionality of the apparatus and the possibility of using it to evaluate the degree of clogging and incrustation of an extraction well. The pilot tests thus demonstrated the usability of the INV-FLOW apparatus. The extraction well operator can assess the level of clogging or incrustation of the extraction well and decide on the need for the rehabilitation of an extraction well, or the termination of its operation.

A study on structure improvement scheme of electromagnetic flow sensor for slurry flow measurement

A scheme to improve the structure of electromagnetic flow sensor is put forward in this paper, which can effectively solve the slurry noise problem when electromagnetic flowmeter measures slurry fluid. The electromagnetic flow sensor used for measuring slurry fluid has slurry noise interference in the measurement signal. At present, the method of increasing the excitation frequency of electromagnetic flow sensor is widely used to overcome slurry noise. However, high excitation frequency will lead to poor stability of zero point. In view of the shortcomings of existing methods, this paper studies the method of improving sensor structure to overcome slurry noise. Firstly, according to the mechanism of slurry noise, an improved scheme for the installation position of the measuring electrode of electromagnetic flow sensor is proposed, which can greatly reduce the probability of solid particles of slurry fluid colliding with the measuring electrode; Then, the relevant research results of bubble dynamics theory are applied to optimize the improvement scheme, and the improvement scheme is determined, through calibration, it is concluded that the improved sensor can reach the accuracy level of 1.0; Finally, through slurry measurement experiments, it is verified that the improved electromagnetic flow sensor can effectively overcome slurry noise.

The Nuclear Magnetic Flowmeter for Monitoring the Consumption and Composition of Oil and Its Complex Mixtures in Real-Time

The necessity of increasing the efficiency of primary oil purification in a drilling station or an offshore platform has been substantiated. We consider the problems that arise during the primary processing of oil mixtures. Important conditions for increasing the efficiency of primary purification (separation) of oil mixtures include measuring the consumption and determining the content of various impurities (water, undissolved particles) and air in them, with an error of no more than 2%. We analyzed the possibilities of using various designs of flowmeters to measure the consumption of the oil mixture coming from a well. It is also necessary to use other measuring instruments to control the state of this mixture, which creates additional problems (searching for an appropriate locations to place them, providing the required operating conditions). Various designs of nuclear magnetic flowmeters–relaxometers were considered, making it possible to measure the consumption of a liquid medium and its times of longitudinal T1 and transverse T2 relaxation with one device. The measured values of T1 and T2 determine the state of the medium. The design of the industrial nuclear magnetic flowmeter–relaxometer M-Phase 5000, which is used to control the flow and quality of oil and oil products, was considered in more detail. Problems were identified that did not allow using this design of a nuclear magnetic flowmeter–relaxometer in a drilling rig or offshore platform. A new design of a nuclear magnetic flowmeter–relaxometer was developed, implementing the methods for measuring q, T1, and T2. These methods and various technical solutions make it possible to use this device at a drilling station or offshore platform. The measurement errors of the consumption q, T1, and T2 were determined. The results of various media studies are presented and compared with q, T1, and T2 measurements on other devices and measured volume (to confirm the adequacy of q measurements). The application scopes of the developed nuclear magnetic flowmeter–relaxometer were determined, in addition to the systems of primary oil processing.

Impact of electro-magneto-hydrodynamics in radiative flow of nanofluids between two rotating plates

Heat transfer improvement using electro-magneto hydrodynamics is a technique that can result in significant heat exchanger reduction as well as “on-demand” heat transfer. Electrohydrodynamic (EHD) is a multidisciplinary science that studies how fluids interact with electric fields or charges. It has been found applications in many areas such as EHD pump, EHD enhanced heat transfer, microelectromechanical systems (MEMS) and other industrial processes. MHD offers a broad array of applications for researchers in astrophysics, planetary magnetic fields, generators, flow meters, metallurgy, metal dispersion (granulation), ship propulsion, crystal development, magnetic filtration, and fusion reactors. Investigation of the mass and heat transfer properties of hybrid nanofluid Transformeroil+TiO2+Fe3O4 in three dimensions is considered. In this research, cumulative effects of magnetic and electric hydrodynamic are examined between two rotating plates in viscous hybrid nanofluid. To generate the hybrid nanofluid, transformer oil is utilized as a base fluid in the nanoparticles TiO2 andFe3O4. Using a similarity approach, the flow model in the form of PDEs is reduced to a system of dimensionless ODEs. The obtained equations are solved by using a shooting (bvp4c) method to attain a numeric solution. Reynolds number, rotational factors and effects of magnetic and electric properties in hydrodynamics have all been researched and argued about thermal efficiency, drag force, and mass flux. Numerical data of Nusselt number, Sherwood number, and drag forces are calculated. By minimizing the influence of physical constraints, the hybrid nanofluid enhances heat transfer rate and mass transport.

Evaluation of discharge measurements methods in a natural river of low or middle flow using an electromagnetic flow meter

AbstractMeasurement of river discharge should be accurate, as it is key environmental data and essential for hydrologic simulations, regardless of whether the flow is high, medium, or low. Herein, conventional methods based on velocity measurements at different depths (i.e., one‐point method, two‐point method, and three‐point method) are evaluated with a method using a surface velocity index and a method based on the entropy theory to estimate river discharge. All the methods were implemented to calculate the discharge of Agios Germanos River, located in Northern Greece, based on 2 years of measurement. Considering that the uncertainty in flow measurement is decreasing by increasing the number of velocity measurements points (EN ISO, 2007), in this work, the reference method is the conventional three‐point method. Results show that the other two conventional methods (the one‐point and the two‐point) estimate the discharge with an error of about 3%, while the error of the other two methods ranges between 11 and 14%. Nevertheless, the nonconventional methods could be considered acceptable and could be used safely to minimize time and subsequently, the cost of field measurements.

A new approach to measure gas holdup in industrial flotation Machines. Part III: Industrial prototype design and assessment

• An industrial gas holdup sensor prototype was validated in a 250 m 3 flotation cell at Los Pelambres. • A weakly dependence of sensoŕs discharge coefficient to Reynolds number was observed. • Gas holdup predictions were largely insensitive to errors in the anticipated pulp kinematic viscosity. • Submersible sensor provided robust accurate gas holdup measurement over long periods of time. An industrial gas holdup sensor was designed, constructed, and its performance assessed on a 250 m 3 self-aerated Wemco cell at Los Pelambres concentrator. The submersible sensor comprised a ceramic-liner IP68 magnetic flowmeter assembled to a stainless steel gas exclusion cell, which resembles an inverted truncated cone. The gas exclusion cell was designed to avoid low-velocity sections where particles could settle. When the sensor device is vertically immersed in an aerated pulp a continuous downward flow of pulp without bubbles is induced through it. A remotely installed processing unit converts the flow velocity signal, provided by the magnetic meter, into a gas holdup signal, by applying Bernoullís equation to the induced flow. The ideal velocity in the Bernoullís equation is obtained by multiplying the measured velocity and the discharge coefficient. The discharge coefficient was found to be fairly constant over a wide range of Reynolds numbers. Gas holdup measurements were compared against those obtained by sampling a fixed volume of aerated pulp using the JK Tech Air Holdup Probe. These tests were conducted on different days over nine months to allow for the pulp properties to change. Gas holdup changes in the flotation machine were achieved by restricting the air intake to the cell by placing a stainless steel cap on top of the air suction pipe. Short and long-term testing demonstrated the sensoŕs capability to provide reliable and accurate continuous-time gas holdup measurements for industrial flotation machines.

The effect of high‐fidelity flow models on electromagnetic flowmeter analysis

AbstractThe current research is unclear regarding the sensitivity of the output of a magnetic flowmeter analysis to the fidelity of the simulated flow field. This study evaluates the effects of higher fidelity models on magnetic flowmeter analysis. An eddy viscosity model, second‐moment closure model, and a Large‐Eddy simulation were compared to laboratory velocity profile data 0.67D downstream of a 1.58D elbow at a Reynolds number of 34,000. The Large‐Eddy simulation results matched the laboratory velocity profile data best. The authors conclude that the fidelity of the flow field model does cause differences in the analysis of the flowmeter voltage output.

The Multifunctional Nuclear Magnetic Flowmeter for Control to the Consumption and Condition of Coolant in Nuclear Reactors

The necessity of coolant flow consumption measurement accuracy increase in the nuclear reactor primary circuit has been substantiated. Additionally, the need to control the coolant condition in the current flow inside the pipeline is shown. Nowadays, the real-time coolant’s condition control function is not implemented at stationary nuclear power plants or mobile nuclear power plants used in moving objects. It is shown that a coolant consumption measurement error decreases and its condition data availability increases the heat transfer efficiency and the electrical energy generation (without the nuclear reactor and steam generator design change). Problems arising during coolant consumption control using various flowmeters models in the nuclear reactor primary circuit are considered. It has been found that nuclear magnetic flowmeters can solve these problems. New difficulties are noted as emerging when using pulsed nuclear magnetic flowmeters designs developed for measuring hydrocarbons, water, biological compounds consumption, and condition control. A new nuclear magnetic flowmeter design has been developed using a modulation technique for nuclear magnetic resonance signal recording. Methods for measuring the coolant flow’s longitudinal T1 and transverse T2 relaxation times are presented. Investigations of coolant flow parameters (consumption and relaxation times) inside the pipeline have been carried out. It is found that the measurement error for these parameters does not exceed 1%. The prospects of using the developed nuclear magnetic flowmeter-relaxometer design in the nuclear reactor first circuit are shown.

Measurement of high-water-content oil-water two-phase flow by electromagnetic flowmeter and differential pressure based on phase-isolation

When the oil field has been exploited by long-term water-flooding, it will be in high water-content stage of production. However, it is a great challenge for high-water-content measurement due to oil droplets extremely dispersed in the water. In this paper, we developed a phase-isolation based method for high-water-content oil-water two-phase flow measurement. Phase-isolation was realized by axial-flow swirler to concentrate scattered and random oil droplets into the pipe center and change the inlet flow pattern into a particular annular flow before measuring. Owing to the axisymmetric velocity and phase distribution, the electromagnetic flow meter avoided the effect of random distribution of insulating phase, and then had a good measurement performance for total volume flow rate. Furthermore, we respectively studied using axial pressure drop, radial pressure drop and the ratio of the two pressure drops to measure water content. The results showed that the ratio of the two pressure drops not only improves the resolution of oil and water, but also effectively reduces the impact of error transfer. In the dual-parameter measurement experiment, the relative errors of total volume flow rate and water content were almost within ±5%.

Evaluation index and performance structure optimization of magnetic field uniformity of complex multiphase flow electromagnetic flowmeter

The uniformity of the excitation magnetic field is an important factor affecting the measurement accuracy of the electromagnetic flowmeter and its adaptability to different flow states of the complex multiphase flow. The main purpose of this paper is to improve the measurement accuracy of electromagnetic flowmeter by improving the uniformity of magnetic field excitation of electromagnetic flowmeter sensor. Firstly, an evaluation index system based on area weight magnetic field deviation degree is established, and the concept of flow state adaptability is put forward. According to this evaluation system, the excitation structure of the conventional electromagnetic flowmeter sensor is improved and optimized, and an excitation model with high uniformity is designed. Meanwhile, the ANSYS software is used for numerical simulation, and normalized standard deviation is used to compare between the new and the traditional electromagnetic flowmeter models. Finally, according to the requirements of the index function, the magnetic pole detection angle of the improved excitation model is simulated and analyzed, and the optimal magnetic pole detection angle is determined to be 45°. On this basis, a new electromagnetic flowmeter is designed for complex multiphase flow at oil wellhead. The field test proves that the measurement error of this flowmeter can reach less than 5%. Compared with the traditional electromagnetic flowmeter, the measurement accuracy has been greatly improved.

Measurement of Oil–Gas–Water Flows in Vertical Pipes Using Electromagnetic Flowmeter and Dual-Conductance Sensors

Three-phase flows are significantly complicated in comparison to single-phase flows and gas–liquid two-phase flows. So far, faced with the presence of two nonconductive dispersed phases in oil–gas–water three-phase flows, the measurement characteristics of electromagnetic flowmeter (EMF) in three-phase flows are an unresolved problem. The flowrate of three-phase flows is difficult to measure due to the nonuniformity arising from interactions between dispersed phases. Aiming at the difficult problem of production logging in oil wells of three-phase flows, this article reports an experimental study on measuring three-phase flows via the EMF and the dual-conductance sensors. Among them, the phase holdups of three-phase flow in vertical pipe are extracted through newly designed distributed coaxial double-ring conductance sensor (DRCS) and rotating electric field conductance sensor (REFCS). A three-phase flow loop test in a pipe of 20 mm inner diameter is carried out. The results show that the EMF has the ability to substantively measure the flowrate of water phase under three flow patterns (bubble, slug, and churn flows) when the water cut is above 60%, and the average absolute percentage deviation (AAPD) for prediction of superficial water velocity is 3.55%. The measurement of superficial gas and oil velocities is implemented by solving the drift-flux models of three-phase flow based on the phase holdups and superficial water velocity, and the AAPDs for predictions of superficial gas and oil velocities are 4.33% and 5.95%, respectively. This research provides a new measurement strategy for production logging of oil, gas, and water three-phase flow production profile by combining the EMF with dual-conductance sensors.

Non-Invasive Groundwater Velocity Measurements Using a Novel Electromagnetic Flowmeter

Tracing groundwater flow is of vital importance for managing water resources and understanding the natural water cycle. However, it is a challenge to make accurate measurements of groundwater flow due to its extremely low velocity. A new electromagnetic flowmeter has been developed to conduct non-invasive groundwater flow velocity measurements. In the setup, a customized trapezoidal current source was connected to a 1 m <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 1 m square coil to generate a strong vertical magnetic field. Two electrodes were used to sense the potential difference caused by water flowing through the magnetic field. A simulation has been developed based on Faraday’s law to evaluate the flow signal under an idealized condition. Two different lab environments have been built for testing the device: an artificial mini-aquifer and a rolling gantry. The measurements show that the flow signal, in practice, generated by the slow-moving water was orders of magnitude smaller than the inductive and capacitive interferences in the system. A linear signal processing model has been developed, allowing the flow signal to be extracted from the measured results. The results show good agreement with simulation and a strong correlation between the flow speed and the processed flow signal, having an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R^{2}$ </tex-math></inline-formula> coefficient of 0.94.

Sensitivity formulation for electromagnetic flow tomography considering the conductivity distribution

The electromagnetic flow tomography (EMFT) technique aims to map the flow velocity profile by interrogating the electromotive force (emf) from the boundary of flow that travels in an electromagnetic field. In principle, the induced potential depends on not only the flow velocity but also the conductivity distribution. In the case of an electromagnetic flowmeter (EMF), the conductivity of fluid is assumed uniform or at least axisymmetric. However, in the case of multi-phase flows, the conductivity distribution is non-uniform and will affect the induced potential distributions. Therefore, applying the EMF model in the non-uniform/asymmetric conductivity distributions will inevitably introduce errors in calculating the velocity profile. In this paper, the forward problem of EMFT has been investigated by taking the conductivity distribution into account. Numerical simulations showed that the proposed non-uniform model has the unique capability in dealing with the fluid of asymmetric and non-uniform conductivity distributions.