Average Wind Velocity Research Articles

Validation of dimensionless method using height average wind velocity for wind forces

Validation of dimensionless method using height average wind velocity for wind forces

Toward the GMF for Wind Speed and Surface Stress Retrieval in Hurricanes Based on the Collocated GPS-Dropsonde and Remote Sensing Data

This article describes the first step toward the development of the geophysical model function (GMF) for the retrieval of wind speed and wind stress in hurricanes, based on developing a relation between the cross-polarized satellite SAR data from Sentinel-1 and winds/stress observed from collocated NOAA GPS-dropsondes data. Field measurements and remote sensing data for tropical cyclones in the Atlantic Ocean were analyzed. Using the data measured by GPS-dropsondes, average wind velocity profiles were obtained, while the parameters of the wind boundary layer (drag coefficient and friction velocity) were restored from the “wake” part of the velocity profiles using the self-similarity property. The self-similarity of the velocity profile “defect” in the boundary layer, known from the fluid dynamics, was used to retrieve the parameters of the atmospheric boundary layer (the surface wind velocity, drag coefficient, and friction velocity) from the dropsonde wind velocity profiles in ten major hurricanes. Based on the processing of the measurements in the hurricanes Irma 2017/09/07 and Maria 2017/09/21 and 2017/09/23 at a time close to the time of acquisition of the Sentinel-1 images, the dependencies of the cross-polarized normalized radar cross section on the wind speed and wind friction velocity were obtained and used for constructing the GMFs.

Plasma polarization electric field derived from radio sounding of solar wind acceleration region with spacecraft signals

Presented is the analytical approximation of averaged solar wind velocity radial dependence in the solar wind acceleration region at heliolatitudes below 60° under low and moderate solar activity. This empirical approximation is based on the data of radio sounding of the solar corona with radio signals from various spacecraft. Deduced is an equation connecting the solar wind velocity radial dependence and the radial dependence of solar wind plasma polarization electric field intensity. This allows constructing a semi-empirical radial dependence of plasma polarization electric field corresponding to the empirical radial dependence of solar wind velocity. Main properties of the semi-empirical dependence, which is based on radio sounding data, are described.

Numerical and experimental investigation of flow in an open-type subsonic wind tunnel

A numerical and experimental investigation of flow, inside the test section of an open-type subsonic wind tunnel, has been incorporated in the present paper. Experimental data are collected at different selected locations along the wind tunnel length and inside the test section. For detail assessment of the spatial variation of flow variables, numerical analysis is carried out. Boundary conditions have a significant influence on the validation of numerical simulation. A novel approach of system curve generation by experimental analysis of wind tunnel is adopted, instead of using the conventional approach of fan-type boundary condition. Mass flow rate and pressure jump obtained by system curve are utilized for inlet and outlet boundary conditions, respectively. Comparison of numerical and experimental flow fields at the test section suggests maximum error of 9.84% in case of area-weighted average wind velocity along the length of the test section, whereas along the height of the test section a maximum error of 7.75% is observed.

Green energy from a hybrid PV panels and wind turbine farm in Lebanon

Abstract The publication presents the results of analysis of green energy from a hybrid PV panels and wind turbine farm use in Lebanon. Electricity is one of the most critical problems in Lebanon. This publication presents an effective solution to this issue. It deals with the generation of green environment friendly electricity from photovoltaic (PV) panels and wind turbine. The genuine idea consists of placing these panels and turbines at the middle of the coastal highway since it is considered as a free land. The produced energy is fed directly to the off gird after being inverted using appropriate devices. The middle of the highway from Tyre to Sidon is considered to apply this research. The actual design consists of 15222 PV panels placed in pairs on a steel chassis among the entire 27300 m coastal distance, 2 meters wide and 7610 vertical axis wind turbines placed at a distance of 0.9 m away from each pair of PV panels. The total energy produced by the PV system is estimated to 7.4 GWh/y and 3.1 GWh/y at an average wind velocity of 4.04 m/s. In addition to its benefit from a free land, the produced energy is environment friendly since there is no carbon dioxide emission.

Wind-induced uplift of exposed geomembrane covers: A proposed revision to conventional design approaches

Conventional approach for exposed geomembrane design assumes that the geomembrane is subjected to an uplift pressure induced by wind above the geomembrane, and the pressure below the geomembrane is kept constant at atmospheric pressure by default. In reality, the exposed geomembrane is typically anchored into subgrade, which limits the exchange of air above and below the geomembrane. Therefore, when the geomembrane is being uplifted, suction will be generated temporarily below the geomembrane. This temporary suction provides significant resistance to uplift during short-duration wind gust. This paper recommended revisions to the current design approach. An average wind velocity within a selected period, instead of the 3-s gust speed, is recommended to be used for design. This period can be selected based on evaluation of how fast air can enter the voids below the geomembrane.

Numerical simulation of a wire–plate solid-state fan for ultra-quiet museum display cases

Conventional microenvironment control systems of a museum display case generally use mechanical fans which produce great noise and vibration for heat dissipation of semiconductor air-conditioning units. Solid-state fans (ionic wind) operate with no moving parts and can overcome noise and vibration issues of a microenvironment control system. In this study, a multi-electrode mathematical and physical model of wire–plate solid-state fans was developed, and its performance has been analysed in depth. Simulation results indicate that there is an optimal distance between discharge electrodes ( d), which corresponds to the largest average wind velocity at the exit of the simulation area ( ua). Under the same power consumption, ua and the vertical height from a discharge electrode to a collecting electrode ( H) exhibit a monotonically increasing relationship. Similarly, ua and the radius of a discharge electrode ( r) show a monotonically decreasing relationship. In addition, a manufactured solid-state fan with an average wind velocity of 1.48 m·s−1 shows a noise intensity of 4.3 dB(A), which is considerably lower than that of a mechanical fan, with the same power consumption. These positive results suggest that ultra-quiet microenvironment control technologies of a museum display case can be potentially developed in the near future.

Simulation Analysis of a Ventilation System in a Smart Broiler Chamber Based on Computational Fluid Dynamics

In this paper, a CFD (computational fluid dynamics) numerical calculation was employed to examine whether the ventilation system of the self-designed smart broiler house meets the requirements of cooling and ventilation for the welfare in poultry breeding. The broiler chamber is powered by two negative pressure fans. The fans are designed with different frequencies for the ventilation system according to the specific air temperature in the broiler chamber. The simulation of ventilation in the empty chamber involved five working conditions in this research. The simulation of ventilation in the broiler chamber and the simulation of the age of air were carried out under three working conditions. According to the measured dimensions of the broiler chamber, a three-dimensional model of the broiler chamber was constructed, and then the model was simplified and meshed in ICEM CFD (integrated computer engineering and manufacturing code for computational fluid dynamics). Two models, i.e., the empty chamber mesh model and the chamber mesh model with block model, were imported in the Fluent software for calculation. In the experiment, 15 measurement points were selected to obtain the simulated and measured values of wind velocity. For the acquired data on wind velocity, the root mean square error (RMSE) was 19.1% and the maximum absolute error was 0.27 m/s, which verified the accuracy of the CFD model in simulating the ventilation system of the broiler chamber. The boundary conditions were further applied to the broiler chamber model to simulate the wind velocity and the age of air. The simulation results show that, when the temperature was between 32 and 34 °C, the average wind velocity on the plane of the corresponding broiler chamber (Y = 0.2 m) was higher than 0.8 m/s, which meets the requirement of comfortable breeding. At the lowest frequency of the fan, the oldest age of air was less than 150 s, which meets the basic requirement for broiler chamber design. An optimization idea is proposed for the age of air analysis under three working conditions to improve the structure of this smart broiler chamber.

Bulk models of sheared boundary layer convection

The paper discusses approaches to the construction of integral models of the convective boundary layer (CBL), based on the concept of complete mixing. To test analytic bulk models and the basic hypotheses of similarity, we use the results of eddy modeling (LES – Large Eddy Simulation). The empirical constants of the CBL integral models obtained according to the LES data for the case of free convection, are in good agreement with the previously published data of laboratory experiments. It is also shown that the flow of kinetic energy from the upper boundary of the CPS, carried out by gravitational waves, is small compared with other components of the balance of turbulent kinetic energy (TKE) in the convective layer. Parametrization of TKE generation for the case of sheared convective boundary layer in terms of the friction velocity and the average wind velocity in the CBL derived; resulting dimensionless constants are obtained from LES data. The results of the work allow us to formulate an integral model of the shear KPS suitable for practical use.

A parametric study of the effect of building layout on wind flow over an urban area

Exploration of the morphological characteristics of buildings in an urban area promotes an understanding of the complex interaction between the layout of building and the wind that flows over them. Based on an interdisciplinary study of building layout, a parameterization of layouts is presented. The wind network index (Rw) exhibits a high performance in distinguishing the effect of layout on aerodynamic characteristics. The physical interpretation of a smaller Rw indicates a higher accessibility of wind passages in the building area. Five types of layouts are presented based on identical planar area density, frontal area density, and cuboid roughness. Wind tunnel experiments evaluate the performance of Rw by measuring spatial average velocity, surface pressure on individual buildings, and total drag force. Results indicate that building layout has a significant influence on the spatial average velocity of wind near the buildings. Distributions of the local drag coefficient from pressure measurements illustrate a relatively flat trend at downstream area in cases of high Rw with insufficient ventilation. Maximum values for overall drag, downstream fluctuation, and velocity attenuation are apparent in the diagonal-grid case. Moreover, a negative correlation is indicated obviously between the overall drag versus layout and the spatial-average velocity versus layout. Results of the drag variation as a function of layout show a similar trend as the drag effect change with the planar area density. Therefore, this study may help to elucidate the effects of building layout on the drag effect and to improve the numerical precision of urban canopy models.

Dynamics of the Kinetic Energy in the Atmospheric Boundary Layer from the Results of Minisodar Measurements

Based on acoustic remote measurements of vertical profiles of three wind velocity components in a 200-meter boundary layer of the atmosphere, values of the kinetic energy of the atmosphere and its components: kinetic energy of ordered motion EMKE (with average wind velocity) and turbulent kinetic energy ETKE are estimated. An analysis of their vertical profiles has demonstrated that at altitudes up to ~25–50 m, the turbulent kinetic energy values and their spreads are very small and sharply increase with altitude. The maximum ETKE values are observed at midnight, as well as the maximum EMKE values. In the morning, the contribution of the kinetic energy of the ordered motion in the lower 100-meter layer of the atmosphere exceeds that of the turbulent motion, which can be caused by the presence of a wind shear in the corresponding wind velocity profiles. The vertical EMKE profile increases in the morning, reaches maximum values by noon, and then decreases by midnight. The diurnal variations of the kinetic energy are characterized by the presence of several minima and maxima whose values and times of occurrence depend on the meteorological conditions during sounding session, the presence and characteristics of cloudiness, and the solar radiation intensity.

Experimental Study of the Wake Regions in Wind Farms

It is desired, through this work, to investigate in detail the scenario that takes place behind a single wind turbine unit by focusing on three parameters; average axial wind velocity component, velocity deficit, and total turbulence intensity. The testing was done at mainstream velocity, U∞, of 5.2 m/s, u and v velocity components were captured by x-probe dual-sensor hot wire anemometer. A massive amount of point data was obtained, which then processed by a matlab script to plot the desired contours through the successive transverse sections along the entire length of the test section. By monitoring the previously mentioned flow parameters, the regions of low velocity and high turbulence can be avoided, while the location of the subsequent wind turbine is selected. The estimation of the distance, at which the inlet flow field will restore its original characteristics after being mixed through the rotor blades, is very important as this is the distance that should separate two successive turbines in an inline configuration wind farm to guarantee the optimum performance and to extract the maximum power out of the subsequent array of turbines. It is found that the hub height axial velocity recovery at six rotor diameters downstream distance is only 82%. This fact means that the power extraction out of the downstream turbine in an inline configuration wind farm is only 55% of the upstream turbine if the same free stream velocity and blade design are adopted.

Analysis of wind energy potential and wind energy development to evaluate performance of wind turbine installation in Bali, Indonesia

In recent years, Wind power generation in Indonesia is no longer a new issue. Indonesia has average velocity from 2 m/s to 7 m/s. With the characteristic it, Indonesia is suitable for small (10 kW) and medium wind turbine installation (10-100 kW. Based on the monitoring data from meteorological, climatological, and geophysical agency (BMKG), the average wind velocity in Bali is 2 m/s – 5m/s, hence Bali has potential to development and utilization the source for wind turbine installation, There are four stations of BMKG in Bali, which each station is supervise the region. Weibull distribution has been represented on this research to calculate and determine the probability of the each of region to know the availibility of the source. Literally, Jembrana station has the lowest availability of power available from the district and cities in Bali, with 0-0.2 W/m2, compared with some districts and cities in Bali, with wind density power between 0-2.88 W/m2 and also the KHK station has the highest probabiity of wind velocity than the other regions. Reconstruction design had been done, with basic data from probability in Bali. The result shows that the redesign of wind turbine give an effective power to extract the wind source.

Bulk Models of Sheared Boundary Layer Convection

The paper discusses approaches to the construction of integral models of the convective boundary layer (CBL), based on the concept of complete mixing. To test analytic bulk models and the basic hypotheses of similarity, we use the results of eddy modeling (LES – Large Eddy Simulation). The empirical constants of the CBL integral models obtained according to the LES data for the case of free convection, are in good agreement with the previously published data of laboratory experiments. It is also shown that the flow of kinetic energy from the upper boundary of the CPS, carried out by gravitational waves, is small compared with other components of the balance of turbulent kinetic energy (TKE) in the convective layer. Parametrization of TKE generation for the case of sheared convective boundary layer in terms of the friction velocity and the average wind velocity in the CBL derived; resulting dimensionless constants are obtained from LES data. The results of the work allow us to formulate an integral model of the shear KPS suitable for practical use.

Forest Fire Trend and Influence of Climate Variability in India: A Geospatial Analysis at National and Local Scale

Abstract Climate change and its severity play an important role in forest fire regime. Analysing the forest fires events becomes a prerequisite for safeguarding the forest from further damage. We have made an assessment of the long-term forest fire events at the district level in India and identified the forest fire hotspot districts. The spatial seasonal (January to June) district wise pattern and forest fire trend were analysed. In the second part of the study area (central part of India), we have evaluated the forest fire events in grid format with respect to the climatic/weather datasets, and the statistical analysis Cramer V coefficient (CVC) was performed to understand its association/relationship with forest fire events. The study revealed that Karbi Anglong and North Cachar Hills districts of Assam of India have the highest forest fire percent among all districts equivalent to 3.4 and 3.2% respectively. Dantewada district of Chhattisgarh and Garhchiroli district of Maharashtra of India occupied 3rd and 4th rank with value 3.1 and 3.0% respectively. The grid-based evaluation (local scale) revealed that most of the fire equivalent of 80% was found in the month of March and April. Forest fire frequency of the month of April is spread over 88 % of the grids over the study area. The 11 years average seasonal month-wise (February to June) maximum temperature, wind velocity, relative humidity, and solar radiation were found in the range of (25.9 to 40.6), (1.69 to 2.7), (0.301 to 0.736) and (14.21 to 22.98) respectively. The percentage increase (in the month of March) of maximum temperature, wind velocity, and solar radiation were 36, 39 and 62% respectively, when compared with the preceding month; whereas, a 60% decrease to relative humidity that was observed in the same month is usually the major cause of forest fire events in the month of March onwards. The evaluation of Cramer V coefficient (CVC) values of rainfall, relative humidity, potential evapotranspiration, maximum temperature, wind velocity, and solar radiation were in decreasing order and in the range of 0.778 to 0.293. The highest value of rainfall (0.778) showed its strongest association with the forest fire events. In the month of June, these areas receive adequate rainfall, which leads to an increase in the soil moisture and a reduction in forest fuel burning capacity by absorbing the moisture and it is a strong reason for less forest fire events during this month. Geospatial technology provides an opportunity to evaluate large datasets over various spatial and temporal scales and help in decision making/formulating various policies.

Study of the effect of natural factors on optimal capacity of renewable energy resources

The paper briefly describes a methodological approach to determine the maximum effective capacity of a renewable energy source for an off-grid consumer, considering natural factors. The annual distribution of indicators of solar and wind energy resources in the northeastern regions of Russia is analyzed. The groups of the characteristic maximum of average monthly wind velocities and the areas of their manifestation are revealed. The results of studying the dependence of the optimal capacity of an off-grid wind power plant on the annual distribution of wind velocities at different wind potential values are presented. The installed capacity utilization factor of wind power plants is shown to depend on natural factors. The results of this study are applied as a basis for guidelines on the priority of using renewable energy sources subject to natural conditions. Keywords: Decentralized consumers, technique to determine optimal capacity, annual distribution, ratio between optimal capacity and consumer’s maximum load.

Faroe Islands: Towards 100% R.E.S. penetration

The Faroe Islands complex consists of 18 islands. The total energy demand is based on imported oil (93%). Electricity needs account for around 10% of the total energy consumption, with 51% covered from wind and hydro in 2016.Annual average wind velocities above 10 m/s and annual rainfalls higher than 3000 mm are measured in several sites. The annual incident solar irradiation on horizontal plane is around 780 kWh/m2. Wind and rain tend to be less in summer, posing a challenge for 100% energy needs cover.This article investigates the perspectives for 100% Renewable Energy Sources (RES) penetration in Faroe, including heating and transportation energy consumptions. Two wind/photovoltaic parks and Pumped Hydro Storage (PHS) systems are investigated for two autonomous systems, the main grid comprising 11 interconnected islands and the autonomous island of Suðuroy, accounting for 10% of the population. Wind potential maps are developed and the PHSs are sited on digitized land terrain. The systems' operation is numerically simulated, aiming at the optimization of the dimensioning. Real demand and RES data are employed. It is shown that RES annual penetration higher than 90% can be approached with RES – storage power plants absolutely technically and economically feasible.

A novel curtain design to enhance the aerodynamic performance of Invelox: A steady-RANS numerical simulation

Invelox is a patented structure designed to capture the incident wind from every direction, guide the collected wind to the ground level and increase its velocity. Previous numerical studies have revealed that a considerable portion of the collected wind escapes the structure from the opposite side of the wind entering Invelox. In the present study, three possible curtain designs are proposed to reduce or fully-eliminate this escaping air. The improved capability of Invelox to augment the wind velocity using these curtain systems is evaluated via numerical simulations. The results show that the best configuration can fully eliminate the escaping air and it will not disturb the air flow uniformity inside the Venturi section. On average, the best design can lead to a 25% increase in the average wind velocity inside the Venturi for the wind velocities of 3–12 m/s. The results also show that although it has been claimed that Invelox accepts wind from all directions, it can only be efficient at the incident wind directions of −90 to 90°. Increasing the turbulent intensity of the upcoming wind from 0 to 20%, however, has no considerable effects on the Invelox speed ratio.

Pengaruh Desain Interior Diffuser Terhadap Peningkatan Performa Diffuser Augmented Wind Turbine (DAWT)

The main objective of numerical simulation in thisstudies is to determine the effect of diffuser’s interior design onincreasing the diffuser augmented wind turbine (DAWT)performance by observing wind velocity increment. Numericalstudies were carried out using the computational Fluid Dynamics(CFD) method through a two-dimensional steady approach withAnsys Fluent 18.2 and Ansys Workbench 18.2 software. Thepresent studies spesifically investigate the shapes of diffuser,namely flat diffuser and curved diffuser. The studies demonstratethat the curved diffuser generates stronger increment of the windvelocity than flat diffuser (at centreline), which 1.842 times thefreestream velocity, while the flat diffuser is only able to increseup to 1.742 times the freestream velocity. The curved diffusershows the highest increment of the average wind velocity alongdiffuser with the greatest increment of 78.66 % and the flatdiffuser is only able to provide average wind velocity incrementup to 44.81%. The curved interor of diffuser is able to enlarge thewake area, so the effect of the suction flow entering the diffuserbecomes stronger. Therefore, curved diffuser is better to provideDAWT performance improvements.

Thermal Analysis of Radial Piezoelectric-Magnetic Fan (RPMF) for Electronics Cooling

Application of piezoelectric fan in electronic cooling system has been proven that it is more efficient than natural convection with least power consumption and has high potential to replace existing rotary fan for its simplicity and longer life. An integration of piezoelectric fan with magnet is to widen the cooling coverage area with similar power consumption and cost of running a single piezoelectric fan. By optimizing the repulsive magnetic force generated in between the magnets, the overall fans oscillate with significant average amplitude. The purpose of this paper is to investigate the performance of multiple piezoelectric-magnetic fan and its significance in reducing temperature while enhance the heat transfer. The parameters under investigation are the distance between magnets and fans orientation. In this study four magnetic fans were activated by a piezoelectric fan. It is found that at distance between magnets is 14 millimeters; the average amplitude is largest at highest resonant frequency. The multiple fans is better to be arranged in radial orientation for its ability to produce larger repulsive magnetic force to oscillate the adjacent fans. The distribution of repulsive magnetic force in radial orientation is five times better than array orientation. Therefore, radial piezoelectric-magnetic fan (RPMF) produces larger average amplitude of fans which is 111%. 30% of power consumption per unit coverage area is secured. RPMF generates average wind velocity of 0.4m/s compared to array orientation 0.17m/s.