Changes In Wind Velocity Research Articles

Quantification of surface layer turbulence using sensible heat values from energy balance versus aerodynamic methods

Surface layer optical turbulence values in the form of the refractive index structure function C n 2 are often calculated from surface layer temperature, moisture, and wind characteristics and compared to measurements from sonic anemometers, differential temperature sensors, and imaging systems. A key derived component needed in the surface layer turbulence calculations is the sensible heat value. Typically, the sensible heat is calculated using the bulk aerodynamic method that assumes a certain surface roughness and a friction velocity that approximates the turbulence drag on temperature and moisture mixing from the change in the average surface layer vertical wind velocity. These assumptions/approximations generally only apply in free convection conditions. To obtain the sensible heat, a more robust method, which applies when free convection conditions are not occurring, is via an energy balance method such as the Bowen ratio method. The use of the Bowen ratio––the ratio of sensible heat flux to latent heat flux––allows a more direct assessment of the optical turbulence-driving surface layer sensible heat flux than do more traditional assessments of surface layer sensible heat flux. This study compares surface layer C n 2 values using sensible heat values from the bulk aerodynamic and energy balance methods to quantifications from sonic anemometers posted at different heights on a sensor tower. The research shows that the sensible heat obtained via the Bowen ratio method provides a simpler, more reliable, and more accurate way to calculate surface layer C n 2 values than what is required to make such calculations from bulk aerodynamic method-obtained sensible heat.

Research on dynamic PI parameter tuning of double-fed wind turbine based on ant colony algorithm

Considering the drawbacks of flexible adjustment of PI controller control parameters in the constant pressure control system of doubly fed fans, a PI controller control parameter flexible adjustment method considering ant colony optimization algorithm (ACO) is proposed. This method uses the proportional coefficient and integration time parameters in the PI controller as the ants in the ant colony optimization algorithm, and the ultimate optimization goal is to control the absolute error integration function. During the control process, the parameters of the PI controller are dynamically adjusted. When the electrified wire netting IR-drop and wind velocity changes, a comparative analysis of the dynamic tuning PI controller parameters and the non-dynamic tuning method was conducted. At last, the simulation studies have shown that the constant voltage control system using the PI parameter Flexible adjustment control method found on ACO can rapidly improve the grid voltage stability of double-fed wind turbines and reduce response time.

A Novel Hybrid Whale Optimization Algorithm Differential Evolution Algorithm-Based Maximum Power Point Tracking Employed Wind Energy Conversion Systems for Water Pumping Applications: Practical Realization

This article describes the implementation of a proposed hybrid whale optimization algorithm differential evolution (WOADE) as a maximum power point tracking (MPPT) for wind energy conversion systems (WECS) employed for water pumping applications. The proposed hybrid MPPT algorithm provides rapid and zero oscillation power tracking to achieve the global maximum power point (GMPP) within a limited number of iterations. In this work, the exploitation capability of the whale optimization algorithm (WOA) is integrated with the exploration behavior of differential evolution (DE) to improve the tracking ability over a steady and dynamic operating climate. The performance of a permanent magnet synchronous generator (PMSG) driven centrifugal pump for water pumping applications with wind energy conversion systems has also been investigated. A modified Ćuk converter provides a higher output voltage with an enhanced voltage conversion ratio and is employed for optimal wind power tracking. The practical realization is done to substantiate the productiveness of the introduced hybrid WOADE based MPPT algorithm for WECS applied for water pumping under varying and sudden changes in wind velocity.

Experimental Analysis on the Behaviors of a Laboratory Surface Fire Spreading across a Firebreak with Different Winds

In this work, a series of laboratory surface fire experiments were performed over a pine needle fuel bed to investigate the effectiveness of a firebreak and the behaviors of a surface fire across a firebreak. Seven wind velocities of 0~3.0 m/s and six firebreak widths of 10~35 cm are varied. The behaviors of a surface fire across the firebreak, the heat flux received by fuel surface and fuel temperature before and after the firebreak are analyzed and compared simultaneously. The main conclusions are as follows: the behaviors of a surface fire spreading across a firebreak under different wind velocities are classified into three categories—no ignition, ignition by flame contact and ignition by spot fires. When the wind velocity is not more than 1.0 m/s, the surface fire cannot successfully cross the firebreak; as wind velocity changes from 1.5 m/s to 2.5 m/s, the fuel after the firebreak can be ignited by flame contact for relatively narrow firebreak conditions; when the wind velocity increases to 3.0 m/s, the burning fuel can be blown away along the fuel bed, and the fuel behind the firebreak will be ignited by spot fire. A linear relationship between the threshold of firebreak width and the fireline intensity is obtained, and the linear fitting coefficient in this paper is larger than the results reported by Wilson (0.36). For no ignition conditions, the fuel temperature and the heat flux received by the fuel after firebreak are significantly lower than those before the firebreak, whereas their variations over time are similar to those before the firebreak for ignition conditions. Moreover, for no ignition conditions, the maximum fuel temperature and the heat flux after the firebreak increase with wind velocity, but decrease with firebreak width. Additionally, when the fuel temperature (253 °C) and the heat flux received by the fuel considering the radiation and convection (43 kW/m2) after firebreak exceed a threshold value, the surface fire can successfully cross the firebreak.

Investigating the influence of 3D building models on pedestrian wind comfort through wind computational fluid dynamics analysis

Wind flow plays a crucial role in determining pedestrian comfortability in the surrounding environment. However, the shape and detailing of buildings, as well as the angle of the wind, can manipulate the wind flow patterns and velocity. Different urbanized areas have different building shapes and detailing, which can lead to diverse wind flow patterns and velocities, affecting pedestrian wind comfort (PWC). This study utilized wind Computational Fluid Dynamics (CFD) technique to investigate the influence of building models on wind velocity and its impact on PWC. The CFD simulation integrated with a 3D urbanized building model provided wind velocity values throughout the study area, which were used to analyze wind comfort at 1.75m elevation based on Beaufort wind force criteria. The study found that diverse effects due to different building detailing were observed, leading to multiple flow patterns and changes in wind velocity. The downstream building recorded a lower velocity value than the upstream building mainly because of wind flow separation from the building frontal. Wind comfort levels were represented using the Beaufort wind force scale (BWS), and all values fell in level 2 and 3, indicating good wind comfort level because of the BWS ≤ 3. This study highlights the significance of building models in determining wind flow patterns and velocity, which ultimately impacts PWC. Despite the study area involving multiple buildings with different shapes and detailing, the wind comfort levels were found to be suitable for pedestrians.

Statistical analysis of equatorial electrojet responses to the transient changes of solar wind conditions

Introduction: Prior case studies have indicated that changes in solar wind conditions have a significant impact on equatorial ionospheric electrodynamics. However, there have been limited statistical studies on this topic, impairing our understanding of the coupling between solar wind, magnetosphere, and equatorial ionosphere electrodynamics.Methods: In this study, we conducted a superposed epoch analysis of long-term data from the South America equatorial electrojet (EEJ) spanning from 2001 to 2021 examining the responses of the equatorial ionospheric electric field to step-like changes in solar wind velocity, density, dynamic pressure, and interplanetary magnetic field (IMF) Bz.Result: Our study shows that step-like changes in solar wind velocity, density, and dynamic pressure can trigger changes in EEJ within ∼20–40 min. EEJ exhibits the highest sensitivity to variations in solar wind velocity while being relatively less sensitive to changes in dynamic pressure. Furthermore, the response of EEJ shows greater responsiveness to northward IMF Bz compared to southward IMF Bz.Discussion: Our work provides statistical evidence of how changes in solar wind can lead to changes in low-latitude ionospheric EEJ. We inferred that the changes in solar wind conditions cause magnetospheric deformation and changes in magnetic reconnection rates, leading to the fluctuations of the ionospheric electric field and the resultant EEJ variations.

Lyapunov based Control Strategy for DFIG based Wind Turbines to Enhance stability and Power

The Doubly Fed Induction Generators (DFIG) based wind turbine is fed with maximum power point tracking is presented in this paper in proposed technique the proportional coefficient tuned adaptively as per wind changes and compare with traditional approaches. This novel method uses three control laws to adjust the proportional gain adaptively to wind speed variations. The intended electrical torque is determined via feedback linearization in the first control law, which makes the assumption that the power capture coefficient and target rotor speed are instantly determined. The second control law uses a Lyapunov-based analysis to determine the power capture coefficient as per changes in wind speed, and the third control law establishes the required rotor speed. As a result of these control principles, the operating point of the turbine shifts in a direction that increases the power capture coefficient, leading the rotor speed to adaptively adjust in the direction of the desired speed. The proposed maximum power tracking method differentiates itself from the perturb-and-observe strategy by removing the need to include a dither or perturbation signal and reliably slipstram the trajectory of maximum power points even in the circumstance of a sudden change in wind velocity, which can cause the perturb-and-observe practice to fail.

Methodology for Determining Heat Losses through Translucent Construction

The purpose of this work is to determine the heat transfer coefficient of translucent fences, considering the number of storeys of buildings, climatic factors, such as wind velocity and outdoor temperature. To achieve this goal, the following tasks were solved: analysis of heat transfer in translucent enclosures as a quasi-stationary process; analysis of heat transfer processes in translucent barriers, which are a combination of solid transparent plates and air gaps connected by a frame structure; determination of the heat transfer coefficient on the glass surface depending on climatic factors and the radiant component. The most important result is the empirical dependence of the heat transfer coefficient on the outer surface of the window block on the Reynolds criterion, the dependences for determining the heat transfer coefficient of window blocks are improved, considering climatic parameters. The heat transfer coefficient of the window block as a whole is presented in the form of analytical ratios, considering the location of the building and its height, changes in wind velocity and outdoor temperature. This methodology was tested on the example of a civil administrative building, for which the heat transfer coefficients of window structures of non-standard series were evaluated. The significance of the research results lies in the possibility of using the obtained dependencies to assess the thermal characteristics of window structures of non-standard shapes. The dependences of the heat transfer coefficient on wind speed and outside air temperature given in the paper can be used in the energy audit of buildings.

Photovoltaic power resource at the Atacama Desert under climate change

The Atacama desert is a region with exceptional conditions for solar power production. However, despite its relevance, the impact of climate change on this resource in this region has barely been studied. Here, we use regional climate models to explore how climate change will affect the photovoltaic solar power resource per square meter (PVres) in Atacama.Models project average reductions in PVres of 1.5% and 1.7% under an RCP8.5 scenario, respectively, for 2021-2040 and 2041-2060. Under RCP2.6 and the same periods, reductions range between 1.2% and 0.5%. Also, we study the contribution to future changes in PVres of the downwelling shortwave radiation, air temperature and wind velocity. We find that the contribution from changes in wind velocity is negligible. Future changes of downwelling shortwave radiation, under the RCP8.5 scenario, cause up to 87% of the decrease of PVres for 2021-2040 and 84% for 2041-2060. Rising temperatures due to climate change are responsible for drops in PVres ranging between 13%–19% under RCP2.6 and 14%–16% under RCP8.5.We conclude that climate change has the potential to impact the PVres in the Atacama region while retaining exceptional conditions for solar power production.

SEASON VARIATIONS OF ASTROCLIMATE PARAMETERS FOR THE TERSKOL OBSERVATORY

We present results of the study of seasonal variations of the astroclimate parameters for the Terskol Observatory: wind speed at the level of 200 mbar as a measure of the adaptive optics (AO) applicability, the wind speed altitude distribution, determining the requirements for the AO performance, moisture content to assess the possibility of AO operation in the IR range, the parameters of the mesospheric sodium layer, determining the brightness of the laser reference star for AO systems, in connection with the task of designing adaptive optics for the Zeiss-2000 telescope. Data on surface wind speed and total cloud cover are also analyzed to assess the available observation time. The data of atmospheric reanalysis were used, with the help of which the parameters under consideration have been studied in large astronomical observatories, as well as satellite data of measurements of mesospheric sodium and full-scale changes in surface wind velocity.

Nonlinear Dynamic Analysis of the Wind–Train–Bridge System of a Long-Span Railway Suspension Truss Bridge

In order to study the coupling vibration between a bridge and a train under the action of crosswind loads, a dynamic interaction model of the wind–train–bridge system is established considering the geometric nonlinear factors of a long-span suspension bridge. A calculation frame is composed, and a corresponding computer program is written. A long-span highway–railway suspension bridge scheme is studied as an example. The linear and nonlinear vibration responses of the bridge under the simultaneous action of both train loads and wind loads are compared using the self-written program, and the influence of wind velocity and train speed on the dynamic responses of the bridge is studied. The results show that the large displacement nonlinearity of the structure does not influence the changing tendency of bridge displacement and acceleration time histories, but reduces the maximum values of the responses. The geometric nonlinear influence on the bridge accelerations is more obvious than that on the displacements. The natural frequencies of this long-span suspension bridge are very low and it is sensitive to wind action. The changes in train speed and average wind velocity have a great influence on the maximum value of bridge displacement, especially when the lateral deformation and acceleration increase sharply with the wind velocity, and the coupling vibration between wind, train, and the bridge can easily occur. The research results can provide references for the safe operation and maintenance of long-span bridges.

Linear change and minutes variability of solar wind velocity revealed by FAST

ABSTRACT Observation of Interplanetary Scintillation (IPS) provides an important and effective way to study the solar wind and the space weather. A series of IPS observations were conducted by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The extraordinary sensitivity and the wide frequency coverage make FAST an ideal platform for IPS studies. In this paper, we present some first scientific results from FAST observations of IPS with the L-band receiver. Based on the solar wind velocity fitting values of FAST observations on 2020 September 26–28, we found that the velocity decreases with increasing frequency linearly, which has not yet been reported in literature. And we have also detected a variation of solar wind velocity on a time-scale of 3–5 min, which imply the slow change of the background solar wind, a co-existence of high- and low-speed streams, or a reflect of the quasi-periodic electron-density fluctuations.

MPPT and pitch angle control for wind energy conversion system-Comparison of selected sites in Morocco-

The wind energy source is one of the important renewable energy resources adopted around the world. It's becoming a widespread technology, and it has an interesting potential to produce large amounts of power, and it's considered as a clean energy.Nevertheless, this resource presents several issues, mainly due to its intermittency and the difficulty of reaching an instantaneous maximum power due to the inertia of the mechanical system, the rapid change in wind velocity and also when the wind speed is low in a given area. This paper expose an example of the behavior of a wind energy conversion system (WECS) using MPPT and pitch angle control strategies for different sites in Morocco. The sites involved in this study are Taza, Dakhla, Tangier, Essaouira, and Safi. The conventional control used in the MPPT is the optimal torque control applied with fixed and variable pitch angle. A comparison was performed for the selected sites, by using MATLAB/Simulink R2020a software, to demonstrate the performance of the combined control MPPT and pitch angle control.

Seasonality of phytoplankton community and dynamics of autotrophic carbon in a cold temperate port (Argentina)

The changes within and between seasons in phytoplankton composition and abundance determine the carbon biomass available for upper levels of the food web. Temporal changes in phytoplankton community and environmental parameters in a port in Puerto Madryn, Southwest Atlantic were analysed. During an annual period (2011–2012), samples of surface seawater were collected approximately monthly. We determined phytoplankton community structure (species composition and abundance) and biomass (determined by carbon content and chlorophyll a (Chl a)). Water temperature, salinity and transparency were measured when sampling the surface water and local meteorological data were considered. The main groups observed were diatoms (Bacillariophyta; the most abundant during the concentration peaks of Chl a), dinoflagellates (Dinophyta) and flagellates, which mainly included species of Cryptophyta and Chlorophyta. Diatoms exhibited blooms in March (summer–autumn) and September (spring), represented by Skeletonema costatum and Pseudo-nitzschia spp. respectively. Dinoflagellates contributed to the highest carbon biomass, with peaks in January (summer) and April (autumn), exemplified by Prorocentrum micans and Scrippsiella acuminata, respectively. Temporal differences in community composition were related to the seasonal changes in temperature, solar irradiance, precipitation, salinity and wind velocity. The environmental conditions seem not only to determine the species composition but also cell size distribution: nanoplanktonic (≤ 20 µm) species dominated mainly during late spring, summer and early winter while microplanktonic species (> 20 µm) during late winter and early spring. Our results showed within-season changes and show that not only Chl a, but also carbon content can be considered, as the former is a biased estimator of phytoplankton biomass. This study provides the first seasonally resolved estimation in the area of the carbon biomass available for upper levels of the food web and a necessary information for future scenarios prediction. HIGHLIGHTS• Two diatom blooms were followed by an increase in dinoflagellate abundance.• Annual environmental conditions drive the phytoplankton community structure.• First seasonally estimation of autotrophic biomass availability for Patagonian trophic web.

Decision support for wildfire asset protection: A two-stage stochastic programming approach

During uncontrollable wildfires, decision-makers dispatch vehicles for tasks aimed at reducing the hazard to key assets. The decision-making process is complicated by the need for vehicle capabilities to match asset requirements within time windows determined by the progression of the fire. This is often further complicated by a wind change that is expected but with uncertainty in the timing. This paper aims to provide a decision support approach for determining plans for the deployment of resources under various scenarios. To this end, we solve the Asset Protection Problem (APP) in the context of Australia’s Black Saturday bushfires by developing a two-stage stochastic model. In this problem, we consider uncertainties in the timing of a change in wind velocity in defining various scenarios. We present a dynamic rerouting model and an Adaptive Large Neighbourhood Search (ALNS) algorithm to solve the model in a time efficient manner for decision-makers. A new set of instances were generated using realistic parameters. Thereafter, we evaluate the performance of the proposed approaches through extensive computational experiments. We solve both the two-stage stochastic program and the more limited dynamic rerouting model exactly for small instances. We observe that the restrictions of the dynamic rerouting model yields solutions within a few percent of the two-stage stochastic program. Moreover, the ALNS solution is a good approximation to its exact equivalent but with faster solution times. After further tests, it became apparent that with larger asset numbers the ALNS is the more practical method for operational purposes.

A decomposition approach for the stochastic asset protection problem

The deterministic Asset Protection Problem (APP) involves deploying firefighting resources of various capabilities to service as many community assets as possible within time windows determined by an advancing wildfire. A common situation arising during these situations is a wind change. Forecasts of changes in wind velocity (i.e. direction and speed) are reasonably accurate but there is some uncertainty around the time of a wind change. The timing has implications for which areas, and hence which assets, will be impacted by the wildfire. This presents a difficult problem for an Incident Management Team (IMT) operating under severe time pressure as the wildfire sweeps across the landscape. In this study, we extend the spatial decomposition-based math-heuristic originally developed for the deterministic APP to handle large real life sized stochastic APPs in operational time. This is achieved by regarding the deterministic and stochastic components as a coupled system. A two-stage stochastic programming (TSSP) model is thus only used for a smaller sub-problem around the uncertainty. We found this approach outperformed other methods when tested on a new set of benchmarks. More importantly, the accuracy and solution times make the method suitable for operational purposes.

THE INFLUENCE OF THE CHANGES IN WIND VELOCITY ON THE OUTER HEAT EXCHANGE OF THE BUILDINGS

When choosing architectural and planning solutions, such climatic factors as air temperature and humidity, having scalar quantities, as well as solar radiation, wind and precipitation having vector characteristics, must be taken into account. The calculated climatic parameters for the design of building enclosing structures, heat loss calculations and heat supply regulation are provided in the current documentation on norms and standards. The practical exploitation of various buildings demonstrates that in terms of initial climatic data, the choice of design parameters is not always efficiently justified; hence, the influence of the environment on the heating regime of the structures is insufficient in the estimations and sometimes erroneous. The wind is one of such climatic parameters. Its velocity and repeatability impact the heat exchange of the building structure with the environment as well as the alteration in temperature regime. The wind current towards the building creates additional pressure on the facade of the construction from the wind side direction. This leads, firstly, to air infiltration via the enclosing structures, and secondly, to the rise of heat exchange from the outer surface of the wall on the windward side. Based on estimated and analytical research, the values of the change in wind velocity depending on the altitude were analyzed, and its influence on the heat loss during heating of multi-storey buildings was assessed. The alterations in the wind velocity depending on the altitude were analyzed in the conditions of dense (urban) and broad construction. Besides, the authors presented the dependence of the convective component of the heat transfer coefficient of the outer surface of the structure on the values of the wind velocity. Based on the performed and presented calculations, it can be noticed that the heat transfer of the external structure will be much higher for multi-storey buildings than for mid-rise constructions. Thus, the convective component of the heat transfer coefficient of the outer surface rises by 36 % when the wind velocity increases from 5 m/s to 7 m/s. If not taking into consideration this dependence in the design, it can significantly influence the estimation of heat loss and energy efficiency of buildings, especially when it is about the increased percentage of facades glazing. The authors of the article assessed the heat loss for heating the windward and leeward facades at average values of the outside air temperature during the heating season in Ukraine. Hence, for constructions higher than 70 m with a calculated wind velocity of 5 m/s, heat losses increase from 10 % to 19 %. Such great difference in heat loss between the windward and leeward walls of the building requires increased thermal protection from the prevailing winter winds. Therefore, when designing multi-storey buildings, it is necessary to take into account changes in wind velocity according to the altitude. The obtained results can be useful both for choosing architectural and planning solutions, like the materials for external enclosing structures and for the objective assessment of the wind protection degree of individual buildings and territories.

Impact of CME and HSSW driven geomagnetic storms on thermosphere and ionosphere as observed from mid-latitudes

The present paper reports magnetospheric-thermospheric-ionospheric interactions, observed during geomagnetically disturbed periods in 2015–2016 from mid-latitude stations located in the US-Pacific longitudes (~120°W geographic). These interactions have been analyzed for a series of Coronal Mass Ejection (CME) and High Speed Solar Wind (HSSW) driven geomagnetic storms during the moderate solar activity periods. The geomagnetically disturbed periods under consideration in this paper have an interesting feature of the occurrences of one or more HSSW events following an intense CME driven intense geomagnetic storm. Correlations were observed between the solar and geomagnetic parameters, hemispherically integrated Joule heating, changes in O/N2 ratio, corresponding changes in neutral wind velocities and mid-latitude Vertical Total Electron Content (VTEC) in most of the cases. Prolonged effects of neutral wind driven equatorward plasma transport process were noticed during the period of the summer solstice (June 23–26, 2015) which was correlated with the hemispherically integrated Joule heating and ionospheric conductivities. The effects of storm onset were observed during March 17–18, 2015. The influences of the ‘super-fountain effect’ in terms of Prompt Penetration Electric Field (PPEF) were seen during the main phases of the geomagnetic storms from these mid-latitude stations. This is correlated with the strength of Equatorial Electrojet (EEJ).

Effect of blade pitch angle on the aerodynamic characteristics of a twisted blade horizontal axis wind turbine based on numerical simulations

The present work includes a study of the impact of varying pitch angles and angular velocity on the performance parameters of a horizontal axis wind turbine using computational fluid dynamics. Simulations have been made using commercial Ansys 15 software. Seven pitch angles are chosen for study, i.e., 0° , 5 ° , 10° , 15° , 20° , 25° , and 28°, and two angular velocity values of 1.57 rad/sec and 2.22 rad/sec are used for simulation. The turbulence model used is shear stress transport (SST) K-ω. A detailed study of the influence of pitch angle on the aerodynamic characteristics of the wind turbine is highlighted. Performance parameters like torque and power have been found to exhibit random variability with a change in wind velocity and pitch angle. The verification of computational fluid dynamics (CFD) with the standard empirical formula is highlighted. The best pitch angle is noted for the best power coefficient.

Evidence for distinctive changes in the solar wind helium abundance in solar cycle 24

ABSTRACT The relative abundance of alpha particles with respect to protons, usually expressed as AHe = (nα/np)*100, is known to respond to solar activity, although changes in its behaviour in the last four solar cycles are not known. In this letter, by systematically analysing inter-calibrated AHe data obtained from the first Lagrangian point of the Sun–Earth system, we show that AHe variations are distinctively different in solar cycle 24 as compared to the last three cycles. The frequency of AHe = 2–3 per cent events is significantly higher in slow/intermediate solar winds in solar cycle 24 as opposed to the dominance of the typical AHe = 4–5 per cent events in the previous three cycles. Further, the occurrence of AHe > 10 per cent events is significantly reduced in cycle 24. Not only that the changes in delay of AHe with respect to peak sunspot numbers are less sensitive to changes in solar wind velocity in cycle 24. The investigation suggests that the coronal magnetic field configuration started undergoing systematic changes starting from cycle 23 and this altered magnetic field configuration affected the way helium got processed and depleted in the solar atmosphere.