Wind Field Research Articles

Reproducing vortex-induced vibrations of rooftop twin-mast by multi-scale coupled simulation of urban wind fields

The Shenzhen Electronics Group (SEG) Plaza in Shenzhen, China, experienced visible vibrations attributed to significant vortex-induced vibrations of the large spacing twin-mast atop the building. The vibration event occurred under complex urban wind environments. In order to reproduce wind fields around SEG Plaza, a multiscale simulation was carried out by integrating the Weather Research and Forecasting (WRF) and Computational Fluid Dynamics (CFD) models. The aerodynamic characteristics and wake modes of twin-mast are investigated by a downscale CFD simulation in detail. Finally, vortex-induced vibration (VIV) of twin-mast was analyzed considering fluid-structure interaction. This work reveals that wind conditions during the SEG Plaza vibration incident were appropriate for the VIV occurrence of twin-mast, and the results of VIV simulation agree well with the field monitoring results by computer vision identification. This study effectively reproduces the full pictures of VIVs of the rooftop twin-mast during this rare event, offering a critical view for the analysis of this event.

AC loss analysis on an HTS field winding of the generator with T-A formulation

In this study, we proposed a coupling model utilizing finite element software to estimate AC loss on the high-temperature superconducting (HTS) field winding of a 1 MW generator. The model comprises three distinct physical modules: rotating machinery and magnetic (RMM), electrical circuit (CE) and partial differential equation (PDE). These modules collaborate to resolve the generator's magnetic field distribution, rated output parameters and degree of current magnetization on the HTS field winding, employing Maxwell equations and T-A formulation. Given the placement of the HTS field winding on the rotor core, accurately calculating its loss in an electromagnetic field that varies both temporally and spatially presents a considerable challenge. To address this issue, we adjust the coordinate system within the PDE module to vary with the material rather than space. Our analysis reveals that the instantaneous AC loss of an HTS field winding comprises two primary components: the attenuation envelope and the oscillatory variation, resulting from the charging process and external harmonic magnetic fields. Additionally, we comprehensively discuss and analyze the influence of current excitation speed on instantaneous AC loss. Accurately estimating AC loss in HTS field windings is a critical and meaningful aspect of preliminary machine design. This study provides an essential reference for addressing this issue.

Investigation and Suppression of External Alternating Field of HTS Excitation Coil in Homopolar Inductor Machine

Investigation and Suppression of External Alternating Field of HTS Excitation Coil in Homopolar Inductor Machine

On equatorial spread F occurrence: A multi-dimensional quantitative assessment

The present study investigates the role of gravity wave induced seed perturbations in the occurrence of Equatorial Spread F (ESF) under the influence of the post sunset background conditions modulated by prevailing electrodynamics and neutral wind. Ionospheric foF2 data sets over geomagnetic equatorial station Trivandrum (8.5°N, 77°E and magnetic dip 0.68°N-corresponding to the period of study) corresponding to vernal and autumnal equinoctial periods encompassing high, low and moderate solar activity years, are used for the study. Meridional wind data is obtained either from ESA’s sun-synchronous satellite GOCE (Gravity field and steady-state Ocean Circulation Explorer) or derived using ionosonde h’F (base height of ionosphere at 2.5 MHz) data from Trivandrum (TVM- 8.5°N, 77°E and magnetic dip 0.68°N) and Sriharikota (SHAR−13.7°N, 80.2°E and magnetic dip 6.9°N-for period of study). This particular study is carried out for geomagnetically quiet days of Vernal Equinox (VE) and Autumnal Equinox (AE) seasons, which are most favoured for ESF occurrence over Indian longitudes. Considering thermospheric wind, ion-neutral collisions, and electric field effects in association with gravity wave seed, threshold curve is generated, which clearly demarcates ESF and NSF (Non spread F) days. Previous studies have addressed ESF variability in electrodynamical domain alone (wherein the layer is above a threshold level). The present study, for the first time, succeeds in demarcating ESF and NSF days by incorporating effects of electric field, neutral wind, collisional RT instability term, and gravity wave seed perturbations simultaneously irrespective of threshold height.

An Alternative Model for the Orbital Decay of M82 X-2: The Anomalous Magnetic Braking of a Bp Star

Recently, the first pulsating ultraluminous X-ray source M82 X-2 was reported to be experiencing a rapid orbital decay at a rate of Ṗ=−(5.69±0.24)×10−8ss−1 based on 7 yr NuSTAR data. To account for the observed orbital-period derivative, it requires a mass transfer rate of ∼200Ṁedd ( Ṁedd is the Eddington accretion rate) from the donor star to the accreting neutron star. However, other potential models cannot be completely excluded. In this work, we propose an anomalous magnetic braking (AMB) model to interpret the detected orbital decay of M82 X-2. If the donor star is an Ap/Bp star with an anomalously strong magnetic field, the magnetic coupling between strong surface magnetic field and irradiation-driven wind from the surface of the donor star could cause an efficient angular-momentum loss, driving a rapid orbital decay observed in M82 X-2. The AMB mechanism of an Ap/Bp star with a mass of 5.0–15.0 M ⊙ and a surface magnetic field of 3000–4500 G could produce the observed Ṗ of M82 X-2. We also discuss the possibility of other alternative models including the companion star expansion and a surrounding circumbinary disk.

Temperature Field Distribution and Thermal Stress Analysis of Pumped Storage Electric Motors

Abstract With the increasingly important role of pumped storage in energy systems, new and higher requirements have been put forward for the operation, safety, and economy of pumped storage power plants. The article takes a three-phase salient pole synchronous pumped storage motor as the research object, by using ANSYS finite element analysis software, a finite element model of a three-phase synchronous generator motor was established to analyze the internal temperature field distribution and thermal stress distribution of the motor. The results show that the higher temperature region of the entire system was concentrated at the winding, followed by the stator and rotor. Therefore, when optimizing the design of the motor in the future, the first step should be to start from the winding. The analysis of the thermal stress situation of the stator shows that the thermal stress and strain were mainly distributed at the inner diameter of the stator core, which was consistent with the distribution of the temperature field at the stator. The results of this study can provide theoretical guidance for the key maintenance areas and maintenance time of pumped storage power generation motors.

Adaptive Wind Field Estimation Using an Empirical Bayesian Approach

In lidar-based gust load alleviation, the wind profile ahead of the aircraft cannot be measured directly but has to be reconstructed (estimated) based on the acquired line-of-sight measurements. Such wind reconstruction algorithms typically include regularization in order to adequately handle the noise within the data. This paper presents an empirical Bayesian approach to choosing optimal regularization parameters for any given set of measurements. Using simulations of flight through turbulence, the Bayesian approach is compared with a former approach (based on engineering guess) and an omniscient optimizer, which yields the best achievable results for a constant set of parameters by using the full knowledge of the wind field. The Bayesian approach is shown to outperform the engineering guess and performs close to the omniscient optimizer while purely relying on the lidar measurement data.

Output power prediction of stratospheric airship solar array based on surrogate model under global wind field

Stratospheric airships are lighter-than-air vehicles capable of continuous flying for months. The energy balance of the airship is the key to long-duration flights. The stratospheric airship is entirely powered by the solar array. It is necessary to accurately predict the output power of the array for any flight state. Because of the uneven solar radiation received by the solar array, the traditional model based on components has a slow simulation speed. In this study, a data-driven surrogate modeling approach for prediction the output power of the solar array is proposed. The surrogate model is trained using the samples obtained from the high-accuracy simulation model. By using the input parameter preprocessor, the accuracy of the surrogate model in predicting the output power of the solar array is improved to 98.65%. In addition, the predictive speed of the surrogate model is ten million times faster than the traditional simulation model. Finally, the surrogate model is used to predict the energy balance of stratospheric airships flying throughout the year under actual global wind fields.

Electromagnetic Analysis of the Demo Magnet System: Electrical Behavior of a Toroidal Field Coil During an Electrical Transient

Electromagnetic Analysis of the Demo Magnet System: Electrical Behavior of a Toroidal Field Coil During an Electrical Transient

Detection of Field Coil Short-Circuit Fault in Synchronous Generators Based on Magnetic Bypass Shunt Effect

Detection of Field Coil Short-Circuit Fault in Synchronous Generators Based on Magnetic Bypass Shunt Effect

Design of a 35 kV high-temperature superconducting synchronous machine with optimized field winding

Design of a 35 kV high-temperature superconducting synchronous machine with optimized field winding

Harmonics Orders Modeling of DC Winding Induced Voltage Pulsation in Wound Field Switched Flux Machines Under PWM Excitation

Harmonics Orders Modeling of DC Winding Induced Voltage Pulsation in Wound Field Switched Flux Machines Under PWM Excitation

Characteristic Analysis of Electromagnetic Force in an HTS Field Coil Using a Performance Evaluation System

A performance evaluation system (PES) can experimentally test the structural stability and magnetic field effects of HTS coils against high magnetic fields and electromagnetic forces before mounting the HTS coils on a large-capacity rotating machine. This paper deals with the characteristic analysis of electromagnetic force in an HTS field coil for a 10 MW Class HTS Wind Power Generator using PES. Based on the designed 10 MW class HTS wind power generator, the HTS coils are manufactured and installed in the PES by a support structure, which is designed considering the electromagnetic force (torque) and heat loads in the HTS coil. To check the stress and deformation in the support structure caused by the electromagnetic force generated from the coil, strain gauge sensors were attached to the support structure and measured under full-load conditions. As a result, the maximum magnetic field and electromagnetic force are 2.8 T and 71 kN, respectively. Compared to the analysis results, the magnetic field and generated electromagnetic force in the HTS coil were the same under no-load and full-load conditions. These results will be effectively used to study and fabricate high magnetic field coils for HTS applications, as well as the PES being fabricated.

Closing the gap in the tropics: the added value of radio-occultation data for wind field monitoring across the Equator

Closing the gap in the tropics: the added value of radio-occultation data for wind field monitoring across the Equator

Features of subseasonal concurrent variations between subtropical and polar front jets and their association with temperature anomalies in China

Subseasonal variability of atmospheric circulation in mid-high latitudes is highly correlated to the upper-level jet streams, acting as a major contributor to the global or regional persistent climate anomalies. In this study, the features of subseasonal concurrent variations (SCVs) between East Asian Polar Front Jet (EAPJ) and Subtropical Jet (EASJ), and corresponding atmospheric circulation and temperature anomalies in China are investigated by using the observational data and NCEP/NCAR reanalysis datasets. Results show that the main variability modes of the winter upper-level wind fields on subseasonal time scales are characterized by the meridional shift in opposite directions and out-of-phase variations in the intensity of the EASJ and EAPJ. These concurrent variations between the two jets have a significant oscillation cycle with a period of 10–25 days. Accompanied by the location (intensity) SCV of the two jets, the mid-latitude circulation systems show significant zonal shifts (local intensity changes), resulting in alternations of the atmospheric circulation between zonal and meridional types. The typical meridional circulation is characterized by a strong East Asian trough and its upstream strong high-pressure ridges. Meanwhile, gradient force between Siberian high and the Aleutian low is anomalously strong. As a result, the SCVs between two jets can cause widespread and persistent low temperature anomalies over China, usually lasting more than three days. In the case of the location SCV of the two jets, the low temperature anomalies concentrate in northern China, particularly in north of 40°N. In the case of the intensity SCV of the two jets, the low temperature anomalies occur in most parts of China, notably in south of 40°N. These results are helpful to improve the prediction of atmospheric circulation and temperature anomalies in East Asia during winter.

Spatiotemporal characteristics of mesoscale eddies in the South China Sea and the influence mechanism of Eddy Kinetic Energy

This paper uses 28 years of satellite altimeter fusion data from 1993 to 2020 to identify and track the mesoscale eddies in the South China Sea based on the Sea Level Anomaly (SLA) closed contour method, with the goal of improving our overall understanding of mesoscale eddy activities in the South China Sea and further investigating the ocean dynamic processes in the region, so as to provide fundamental data for climate change studies. The study examined the spatiotemporal distribution, generation and demise, and movement trajectories of the eddies. Furthermore, key parameters including velocity, vortex radius, amplitude and Eddy Kinetic Energy (EKE) were analyzed, with a particular emphasis on the seasonal changes and mechanisms that influence EKE in two areas of the South China Sea with high energy values. The South China Sea has more cyclonic eddies than anticyclonic eddies, according to the study, and its eastern region is primarily home to high-frequency generating areas. However, the majority of the vortices will eventually dissipate in the western and central areas of the South China Sea. Furthermore, vortices usually flow farther to the west. With decreasing latitude, the eddy radius and EKE distribution gradually increase, whereas the amplitude is contrary. EKE is caused by the interaction of factors including wind field driving, seawater movement, and circulation. Seasonal changes in the EKE occur near the Luzon Strait, and the sea area east of the south in Vietnam exhibits clear characteristics.

Evaluation of future wind climate over the Eastern Mediterranean Sea

The aim of this study is to evaluate wind climate characteristics in the Eastern Mediterranean Sea until the end of the 21st century using the wind fields simulated by the EURO-CORDEX Regional Climate Models (RCM), namely the Rossby Centre regional atmospheric model (version RCA4). Long-term averages, long-term trends, and long-term variability in wind characteristics under two Representative Concentration Pathway (RCP 4.5 and 8.5) scenarios were assessed for two future periods: the near future for the years 2021–2060 and the middle future for the years 2061–2100. Relative to the historical period, the most remarkable changes in the mean wind speeds were projected under the RCP 8.5 scenario in the middle future in the central and southern Aegean Sea (exceeding 5 % increase) and in the eastern and northern Levantine basin (up to 5 % decrease), compatible with the definition of the climate scenarios as the RCP8.5 scenario assumes a rising radiative forcing until 2100. The changes in extreme wind characteristics are more noteworthy in agreement with the indicators of climate change (i.e., an increase in the intensity and the frequency of extreme events). 100-year return period wind speed increases by about 29 % in the western Levantine basin under the RCP 8.5 scenario while the most drastic decrease in 100-year extreme wind speed was found in the central Levantine basin with a reduction of exceeding −29 % for the middle future period under the RCP 8.5 scenario. These decreasing and increasing behaviors in extreme wind speeds are expected in the study area as the Mediterranean is affected by many climate systems.

ПЕРЕТВОРЮВАЧ АСИНХРОННОГО ЕЛЕКТРОПРИВОДА ТА ЕЛЕКТРОПРИВОДА ПОСТІЙНОГО СТРУМУ

A converter is considered that canprovide control of both anasynchronous electric drive and a DC electric drive. In an asynchronous electric drive control of a three-phase frequency converter by reactive power; in a DC electric drive the armature voltage is formed by PWM modulation of two arms of the frequency converter, and the voltage of the field winding is PWM modulated by the third arm of the converter. Ensures high-quality control of electric drives. Ref. 10, fig. 3.

Fluctuating wind load encountered by linearly moving vehicles: Investigation on fluctuating wind spectral characteristics

Wind load is one of the controlling loads for moving vehicles. Existing studies on the wind-induced response of vehicles mostly apply traditional wind spectra directly to the vehicles, overlooking their motion status. Fluctuating wind characteristics encountered by linearly moving vehicles were investigated in this paper. The traditional static frame of view was adjusted to a moving one, two principal flow directions were considered and the idea of positional equivalence introduced in Taylor frozen assumption was extended to the moving direction. A fluctuating wind power spectral density (PSD) was proposed. Then a novel test was designed to enable a measuring probe to travel across a wind field. The fluctuating wind characteristics encountered by moving points are quite different from those encountered by a static point. The integral scale decreases as the speed ratio of the measuring point to the wind increases, and an elliptic model was suggested. The proposed PSD aligns well with the test results, indicating that it can be used to accurately characterize the fluctuating wind load encountered by moving vehicles. Both the test results and the numerical analysis showed that as the speed ratio increases, the PSD and energy spectrum as a whole migrate to higher frequencies.

Global Effect of New Active Regions on Coronal Holes and Their Wind Streams

Solar wind prediction algorithms and simulations of coronal events often employ photospheric field maps that are assembled over a 27 day solar rotation. This has stimulated efforts to update and better synchronize the maps by applying flux transport and including observations of the back side of the Sun. Here, using potential-field source-surface extrapolations, we address the question of how the emergence of a large active region (AR) on the Sun’s farside affects the coronal field and configuration of coronal holes on the Earth-facing side. We find that, if the new AR is located ∼135°–180° in longitude from Earth, the effect on the coronal field and solar wind near the central meridian will be almost negligible. This is because, when sunspot activity is relatively low, the outermost AR loops will become connected to the nearby polar fields; when sunspot activity is high, the newly emerged flux will connect to neighboring ARs. However, large ARs that emerge near the solar limb may sometimes have a significant effect on the field near the central meridian. In particular, a coronal hole having opposite polarity to that of the nearest sector of the AR may partially close down, resulting in slower wind; conversely, if the coronal hole has the same polarity as the facing AR sector, it will tend to increase in areal size, resulting in faster wind. In most cases, the main effect of a new AR will be to redistribute open flux between itself and neighboring coronal holes (including the polar holes) through interchange reconnection.