Longitudinal Flux Research Articles

Axial Wind Effects on Stratification and Longitudinal Sediment Transport in a Convergent Estuary During Wet Season

AbstractThe Coupled Ocean‐Atmosphere‐Wave‐Sediment Transport (COAWST) modeling system was used to examine axial wind effects on vertical stratification and sediment transport in a convergent estuary. The model demonstrated that stratification dynamics in the upper estuary (Kelvin number <1; ) are dominated by longitudinal wind straining, whereas the dominant mechanism governing estuarine stratification in the lower estuary (Kelvin number ~1) is lateral wind straining. Barotropic advection contributes to seaward sediment transport and peaks during spring tides, whereas estuarine circulation causes landward sediment transport with a maximum during neap tides. Down‐estuary winds impose no obvious effects on longitudinal sediment flux, whereas up‐estuary winds contribute to enhanced seaward sediment flux by increasing the tidal oscillatory flux. The model also demonstrates that bottom friction is significantly influenced by vertical stratification over channel regions, which is indirectly affected by axial winds.

In-Line Estimation of the Magnetization Curve of Steel Strips in a Continuous Induction Furnace

An in-line parameter estimation strategy for continuous inductive heating of ferromagnetic steel strips is developed and investigated. During strip processing in a longitudinal flux induction furnace, the parameters of the magnetization curve (B-H curve) of the strip material are identified by a moving horizon estimator (MHE). The estimator uses a tailored 2D spatial-temporal model of the furnace which takes into account both the thermal and the electromagnetic subsystem. Other model parameters are identified in a scenario, where the magnetization curve of the strip is known. For model validation, the simulated strip temperature at the furnace exit is compared with measurements. To approximate the solution of the nonlinear Maxwell equations, the effective magnetization approach is applied. Here, a sophisticated hysteretic magnetization model is avoided in favor of the computing time, while magnetic saturation effects in the strip are still captured. The developed MHE is validated in a simulation scenario based on a strip with a known magnetization curve.

Improved Analysis and Modeling of Leakage Inductance for Planar Transformers

Planar transformers have often been mistaken to essentially have lower leakage inductances. The “radial effect” is a natural characteristic for planar windings due to a higher aspect ratio of conductor width to conductor thickness, which gives a reduction in leakage inductance. Traditional formulas for leakage inductance in traditional transformers, where the winding width is much smaller than the winding height, are not suitable for planar transformers. This paper specifically tailors the traditional 1-D solution of leakage inductance by decomposing the leakage flux into longitudinal and transversal fluxes. In this manner, the “eddy current effect” and the “radial effect” in leakage inductance can be analyzed individually. The proposed new formula including both ac (high-frequency eddy current effect) and dc effects (radial effect) offers an accurate prediction of leakage inductance in planar transformers. Finite element analysis and measurements are carried out to validate the proposed formula.

Study of the Effect of Thermal Dispersion on Internal Natural Convection in Porous Media Using Fourier Series

Natural convection in a porous enclosure in the presence of thermal dispersion is investigated. The Fourier–Galerkin (FG) spectral element method is adapted to solve the coupled equations of Darcy’s flow and heat transfer with a full velocity-dependent dispersion tensor, employing the stream function formulation. A sound implementation of the FG method is developed to obtain accurate solutions within affordable computational costs. In the spectral space, the stream function is expressed analytically in terms of temperature, and the spectral system is solved using temperature as the primary unknown. The FG method is compared to finite element solutions obtained using an in-house code (TRACES), OpenGeoSys and COMSOL Multiphysics®. These comparisons show the high accuracy of the FG solution which avoids numerical artifacts related to time and spatial discretization. Several examples having different dispersion coefficients and Rayleigh numbers are tested to analyze the solution behavior and to gain physical insight into the thermal dispersion processes. The effect of thermal dispersion coefficients on heat transfer and convective flow in a porous square cavity has not been investigated previously. Here, taking advantage of the developed FG solution, a detailed parameter sensitivity analysis is carried out to address this gap. In the presence of thermal dispersion, the Rayleigh number mainly affects the convective velocity and the heat flux to the domain. At high Rayleigh numbers, the temperature distribution is mainly controlled by the longitudinal dispersion coefficient. Longitudinal dispersion flux is important along the adiabatic walls while transverse dispersion dominates the heat flux toward the isothermal walls. Correlations between the average Nusselt number and dispersion coefficients are derived for three Rayleigh number regimes.

The reason of occurrence of a longitudinal residual induction of steel spindle after circular magnetization

A special attention is paid to the possibility of appearance of a longitudinal residual magnetic flux leakage (MFL) field in the tested ferromagnetic spindle after its circular magnetization. The reasons of appearance of this field and experimental verification of the interpretation are given. When the occurrence of such field is unacceptable, the spindle has to be demagnetized.

Экспериментальное определение теплопроводности композиционных материалов в широком диапазоне значений при комнатной температуре

In developing new composite materials and solving heat transfer problems, the thermal conductivity is an important characteristic that must be reliably determined. This often requires samples of the smallest dimensions, which is relevant for the production of pilot batches of material, as well as if they are taken directly from the product, when the amount of material is very limited. Most common methods for determining thermal conductivity require samples of relatively large sizes. To measure thermal conductivity on small-sized samples, an upgraded benchtop instrument is introduced. The instrument uses the relative method of longitudinal heat flux, which consists in a comparative measurement of a sample located between the heater and the standard in a stationary thermal mode. This paper presents the instrument design details, the requirements for the samples, explains the calibration features and the measurement procedure. The measurement results in a number of composite materials, as well as in materials with well-studied properties are analyzed. Findings show that the error of determining the thermal conductivity on a modernized instrument does not exceed several percent.

Impact of sand mining on alluvial channel flow characteristics

Mining pit in a channel bed causes disturbance to the flow characteristics. To interpret the phenomenon of change in flow characteristics in a mining pit, experimental study was performed in a tilting laboratory flume. This research focuses on the impact of mining pit on different turbulent parameters, such as flow velocity, Reynolds shear stress distribution, turbulent kinetic energy fluxes, and higher order moment distribution. We have observed dropped in flow velocity in the pit and also significant reversal velocity layer at the pit bottom. The analysis of Reynolds shear stress and higher order moment distribution shows higher values of velocity fluctuations in the pit than the upstream section. The response of bursting events, which is identified by the third order moment, shows influence of sweep events near the bed in all four sections. Third order moment analysis also shows a rise in dominance of sweep events along the flow depth in the pit and it’s downstream, compared to the upstream section. The kurtosis distribution shows highly intermittent nature of turbulence close to the channel bed. The longitudinal turbulent kinetic energy fluxes and vertical turbulent kinetic energy fluxes are in downstream and downward directions for both inner and outer layer in the pit region, which shows an increase in bed particle mobility in that region, whereas it is present only in the inner layer at the upstream section. Additionally, improved bed load transport equation by incorporating pit geometry has been proposed for alluvial channel subjected to sand mining.

Observations of solar small-scale magnetic flux-sheet emergence

Aims. Two types of flux emergence were recently discovered in numerical simulations: magnetic loops and magnetic sheet emergence. While magnetic loop emergence has been documented well in recent years using high-resolution full Stokes data from ground-based telescopes as well as satellites, magnetic sheet emergence is still an understudied process. We report here on the first clear observational evidence of a magnetic sheet emergence and characterise its development. Methods. Full Stokes spectra from the Hinode spectropolarimeter were inverted with the Stokes Inversion based on Response functions (SIR) code to obtain solar atmospheric parameters such as temperature, line-of-sight velocities, and full magnetic field vector information. Results. We analyse a magnetic flux emergence event observed in the quiet-Sun internetwork. After a large-scale appearance of linear polarisation, a magnetic sheet with horizontal magnetic flux density of up to 194 Mx cm−2 hovers in the low photosphere spanning a region of 2–3 arcsec. The magnetic field azimuth obtained through Stokes inversions clearly shows an organised structure of transversal magnetic flux density emerging. The granule below the magnetic flux sheet tears the structure apart leaving the emerged flux to form several magnetic loops at the edges of the granule. Conclusions. A large amount of flux with strong horizontal magnetic fields surfaces through the interplay of buried magnetic flux and convective motions. The magnetic flux emerges within 10 minutes and we find a longitudinal magnetic flux at the foot points of the order of ∼1018 Mx. This is one to two orders of magnitude larger than what has been reported for small-scale magnetic loops. The convective flows feed the newly emerged flux into the pre-existing magnetic population on a granular scale.

Finite element analysis and experiment on induction heating process of slab continuous casting-direct rolling

To reduce the energy consumption of reheating billets between the continuous casting and hot rolling processes, the continuous casting-direct rolling (CC-DR) process is developed, of which one of the key technologies in CC-DR is compensative heating between the processes. Considering the compensative heating technology requirements in the actual production of slab CC-DR, the finite element models of longitudinal flux induction heating (LFIH) and transverse flux induction heating (TFIH) are established to analyse the slab heating process. The results show that LFIH is good for heating surfaces of the slab, but cannot solve the problem of low temperature on the edges, which can effectively be heated with TFIH. The temperature distribution of the slab can be made more uniform by choosing the appropriate current and moving speed. Besides, induction-heating prototypes are developed to inspect the effect of induction heating. The measured results are consistent with the simulated ones. The results of the analysis have direct significance on the induction heating process in the actual production of slab CC-DRs.

Comparison of the Electromagnetic Characteristics of Single-Phase Linear Oscillating Machines according to Magnetic Flux Flow

Linear oscillating machines are typically classified according to flux flow, as longitudinal and transverse flux type devices. In longitudinal flux linear oscillating machines, the direction of the current flow is perpendicular to the direction of the moving part, while the direction of the current flow in transverse flux linear oscillating machines is parallel to the direction of the moving part. Since the direction of the magnetic flux and the current are different in the two models, their electromagnetic characteristics can also be expected to be different. In this paper, we compare the electromagnetic characteristics of these two types of linear oscillating machines. For a fair evaluation of these characteristics, both models are designed to have the same stator outer diameter, permanent magnet volume, and no-load back electromotive force. In characterizing the devices, we analyze air gap flux density, flux linkage, and inductance, as well as the electromagnetic loss.

On a Magnetic Anomaly in the Umbra of the Following Spot of an NOAA 12192 Active Region

This paper examines the evolution and morphology of a magnetic anomaly: the appearance and disappearance of a longitudinal magnetic flux with opposite polarity at an area of about 10 arc seconds in the umbra of the following sunspot of an NOAA 12192 active region, which was observed from 21 to 26 October 2014 in the SDO/HMI and SOLIS/VSM magnetograms. Information collected by spacecraft and under on-ground observations including data from the Sun Service of the Crimean Astrophysical Observatory of the Russian Academy of Sciences are analyzed. Based on the methods of observation and determination of longitudinal magnetic fields in SDO/HMI in line FeI 6173.34 A it was revealed, that combinations of contours appearing due to magnetic force lines inclinations relative to the line-of-sight and line-of-sight velocities can cause a significant undervalue of the magnetic field intensity in magnetograms, but polarity does not reverse. The fine spatial structure, evolution features, close correlation with ultraviolet loops system in SDO/AIA images, “moustaches”, and no temporal and spatial correlation with flares point to a connection between the detected anomaly and the new magnetic flux emergence of opposite polarity in a spot’s umbra at an earlier decay stage. We analyze magnetic force lines reconnection and show that annigilation of the magnetic fields of opposite polarities can take place for many hours at small (~30 km) scales and this fact is verified by observation results. There are additional facts in favor of the cluster model of a solar spot by Severny-Parker.

Multifunctional linear induction motor with longitudinal-transverce magnetic flux for magnetic-levitational transport

Background: Traction linear induction motors (LIM) at the current stage of human society development are the most promising for high-speed magnetic-levitation transport (MLT) and are already used in a number of commercial projects. Linear induction motors can be executed with longitudinal, transverse and longitudinal-transverse magnetic flux and have a large number of design options.
 Aim: In addition to traction efforts, LIM develops the forces of magnetic-levitation and lateral stabilization (self-stabilization). The efforts of magnetic-levitation of linear induction motors with longitudinal and transverse magnetic flux are very significant in the zone of large slides (at low speeds) and decrease with increasing speed of the magnetic-levitation transport. To a lesser extent, the decrease in slip (at high speeds) affects the magnetic-levitation forces developed by a number of design variants of linear induction motors with a longitudinal-transverse magnetic flux, in which magnetic fields traveling in a transverse direction towards each other are additionally used. This is explained by the fact that at high and low velocities MLT, the LIM slip will be equal to unity relatively oppositely running in the transverse direction of the magnetic fields and the magnetic suspension forces will be maximum.
 Materials and Methods: Running towards each other in the transverse direction of the MLT movement, magnetic fields cross the electrically conductive secondary element (playing the role of the track structure of the high-speed transport system) and induce electromotive forces in it, under the influence of which currents will flow.
 Results: As a result, cross counter-directional mechanical forces are created which, in the symmetrical arrangement of the MLT crew relative to the track structure, are mutually balanced and do not have any effect on the motion of the magnetic-levitation transport. At lateral (transverse) displacement of the high-speed transport on the magnetic suspension relative to the track structure, the equilibrium of the transverse mechanical forces is disrupted and, under the effect of the effort difference, the MLT crew will be automatically returned to the original symmetrical position.
 Conclusion: The distribution of magnetomotive forces (MMF) of a linear induction motor with a longitudinal-transverse magnetic flux, whose magnetic system is formed by the combination of longitudinally and transverse laminated cores, on the teeth of which the coils of a concentrated three-phase winding are located, is considered. The relations are represented in the form of a double Fourier series for calculating the resultant MMF value in the air gap of a linear induction motor with a longitudinal-transverse magnetic flux.

An Advanced Equivalent Circuit Model for Linear Induction Motors

In this paper, a distribution function to model the longitudinal end effect for the linear induction motors is developed to predict the variation of the air-gap flux distribution with the slip. The classic equivalent circuit model presented by Duncan is improved by taking the air-gap flux distribution function into account. First, the longitudinal air-gap flux and secondary demagnetizing current distribution function based on the travelling wave theory are proposed to describe the variation of the distributions. Second, an extra magnetizing branch, which takes the output power losses due to the longitudinal end effect into account, is connected in parallel with the existing magnetizing branch of the T-type circuit. Then, two coefficients used for correcting the magnetizing inductance and secondary resistance in the equivalent circuit are obtained. Third, the thrust and vertical force are calculated and compared with the existing model, as well as the efficiency and power factor in a range of rated speed is presented. Finally, these calculated results are validated by measurements on an experimental rig of the linear induction motor.

Gate voltage controlled thermoelectric figure of merit in three-dimensional topological insulator nanowires

The thermoelectric properties of the surface states in three-dimensional topological insulator nanowires are studied. The Seebeck coefficients $S_c$ and the dimensionless thermoelectrical figure of merit $ZT$ are obtained by using the tight-binding Hamiltonian combining with the nonequilibrium Green's function method. They are strongly dependent on the gate voltage and the longitudinal and perpendicular magnetic fields. By changing the gate voltage or magnetic fields, the values of $S_c$ and $ZT$ can be easily controlled. At the zero magnetic fields and zero gate voltage, or at the large perpendicular magnetic field and nonzero gate voltage, $ZT$ has the large value. Owing to the electron-hole symmetry, $S_c$ is an odd function of the Fermi energy while $ZT$ is an even function regardless of the magnetic fields. $S_c$ and $ZT$ show peaks when the quantized transmission coefficient jumps from one plateau to another. The highest peak appears while the Fermi energy is near the Dirac point. At the zero perpendicular magnetic field and zero gate voltage, the height of $n$th peak of $S_C$ is $\frac{k_B}{e}\texttt{ln}2/(|n|+1/2)$ and $\frac{k_B}{e}\texttt{ln}2/|n|$ for the longitudinal magnetic flux $\phi_{\parallel} = 0 $ and $\pi$, respectively. Finally, we also study the effect of disorder and find that $S_c$ and $ZT$ are robust against disorder. In particular, the large value of $ZT$ can survive even if at the strong disorder. These characteristics (that $ZT$ has the large value, is easily regulated, and is robust against the disorder) are very beneficial for the application of the thermoelectricity.

Numerical investigation of effects on blanks for press hardening process during longitudinal flux heating

With the induction heating technology, it is possible to heat up blanks for the press hardening process in 20 s or less. Furthermore, the dimension of an induction system is small and easy to control in comparison to conventional heating systems. To bring the induction heating technology to warm forming industry it is necessary to analyze the process under the view of induction. This paper investigates the edge- and end-effects of a batch heated blank. The results facilitate the later design of induction heating systems for the batch process.

PHYSICAL AND CHEMICAL CONNECTIVITY OF STREAMS AND RIPARIAN WETLANDS TO DOWNSTREAM WATERS: A SYNTHESIS.

Streams, riparian areas, floodplains, alluvial aquifers and downstream waters (e.g., large rivers, lakes, oceans) are interconnected by longitudinal, lateral, and vertical fluxes of water, other materials and energy. Collectively, these interconnected waters are called fluvial hydrosystems. Physical and chemical connectivity within fluvial hydrosystems is created by the transport of nonliving materials (e.g., water, sediment, nutrients, contaminants) which either do or do not chemically change (chemical and physical connections, respectively). A substantial body of evidence unequivocally demonstrates physical and chemical connectivity between streams and riparian wetlands and downstream waters. Streams and riparian wetlands are structurally connected to downstream waters through the network of continuous channels and floodplain form that make these systems physically contiguous, and the very existence of these structures provides strong geomorphologic evidence for connectivity. Functional connections between streams and riparian wetlands and their downstream waters vary geographically and over time, based on proximity, relative size, environmental setting, material disparity, and intervening units. Because of the complexity and dynamic nature of connections among fluvial hydrosystem units, a complete accounting of the physical and chemical connections and their consequences to downstream waters should aggregate over multiple years to decades.

Theoretical basal Ca II fluxes for late-type stars: results from magnetic wave models with time-dependent ionization and multi-level radiation treatments

In the current study we present ab initio numerical computations of the generation and propagation of longitudinal waves in magnetic flux tubes embedded in the atmospheres of late-type stars. The interaction between convective turbulence and the magnetic structure is computed and the obtained longitudinal wave energy flux is used in a self-consistent manner to excite the small-scale magnetic flux tubes. In the current study we reduce the number of assumptions made in our previous studies by considering the full magnetic wave energy fluxes and spectra as well as time-dependent ionization (TDI) of hydrogen, employing multi-level Ca II atomic models, and taking into account departures from local thermodynamic equilibrium. Our models employ the recently confirmed value of the mixing-length parameter $\alpha=1.8$ . Regions with strong magnetic fields (magnetic filling factors of up to 50%) are also considered in the current study. The computed Ca II emission fluxes show a strong dependence on the magnetic filling factors, and the effect of time-dependent ionization (TDI) turns out to be very important in the atmospheres of late-type stars heated by acoustic and magnetic waves. The emitted Ca II fluxes with TDI included into the model are decreased by factors that range from 1.4 to 5.5 for G0V and M0V stars, respectively, compared to models that do not consider TDI. The results of our computations are compared with observations. Excellent agreement between the observed and predicted basal flux is obtained. The predicted trend of Ca II emission flux with magnetic filling factor and stellar surface temperature also agrees well with the observations but the calculated maximum fluxes for stars of different spectral types are about two times lower than observations. Though the longitudinal MHD waves considered here are important for chromosphere heating in high activity stars, additional heating mechanism(s) are apparently present.

Combination Traction and Lateral Stabilisation System for Magnetic Levitation Transport

The problems of improvement of modern types of transport and creation of new ones are important and topical for the human society development. One of the most promising and environmentally-friendly modes of transport is the high-speed maglev transport, moving at speeds of approximately 500 km/h. Objective. Justification of linear induction motor, development and research of various constructions of this type of motors. Methods. Description of linear induction motor with longitudinal and transverse magnetic flux for combined traction and lateral stabilisation system of maglev transport, having increased lateral stabilisation forces. The mathematical modelling of magnetomotive force (MF) in the air gap of traction linear motor of this type has been conducted. To analyse the MF the assumption has been made about even distribution of magnetic induction in the air gap in transverse direction and its sinusoidal longitudinal direction, making it possible to develop new mathematical model of MF distribution in the air gap of linear induction motor with longitudinal and transverse magnetic flux Results. The developed mathematical model for calculation of MF on traction linear machine will enable increasing accuracy of traction and lateral stabilisation combined system forces for maglev transport. The same relates to mutual location of inductor to the secondary element. All this proves the successful ten-year commercial operation experience of magnetically suspended train carrying passengers from an airport to Shanghai, P.R. China. The values of traction and lateral stabilisation forces of linear induction motor with longitudinal and transverse magnetic flux is greatly influenced by the character of current distribution in the secondary element. The character itself is influenced by MF distribution in the air gap.

Analysis of a Direct Drive 2-D Planar Generator for Wave Energy Conversion

In this paper, a novel direct drive, bilateral planar switched reluctance generator (BPSRG) is developed for 2-D wave energy conversion with a mixed type of flux circulation. The proposed BPSRG has longitudinal flux type of the magnetic circuit on one direction and transverse flux-type magnetic circulation for the other perpendicular direction. The characteristics of the magnetic flux and static inductance are calculated for the BPSRG based on the 3-D finite-element method, in order to ensure negligible coupling effect between any phases. Theoretical model of the BPSRG is derived, and parameters that impact the open-loop operation performance of the power generation are analyzed, optimized, and supported by experimental results.

A Novel Structure Single-Phase Tubular Switched Reluctance Linear Motor

Tubular switched reluctance linear motor (TSRLM) has lower loss and higher thrust density than flat-type switched reluctance linear motor. Two kinds of single-phase TSRLMs with different surrounding magnetic flux paths are introduced in this paper. The structure of transverse flux TSRLM (TF-TSRLM) is compared with the structure of the longitudinal flux TSRLM (LF-TSRLM). The structure selection of TF-TSRLM with two poles, four poles, six poles, and eight poles is made for enhancing average electromagnetic thrust. The comparisons between LF-TSRLM and TF-TSRLM are made in the same stator outer diameter, the same mover laminated thickness, and the same excited current on static electromagnetic thrust, magnetization curves, average thrust per unit volume, and average thrust per unit mass. They show that the TF-TSRLM with the six-pole structure is considered as a relatively more reasonable structure for enhancing the space effective utilization rate and increasing the electromagnetic thrust.