Effect Of Different Wind Speeds Research Articles

Wind action on whirling flame characteristics

The behavior of whirling flame above a pool fire under cross wind was studied using a small wind tunnel. Whirling flames with different heat release rates were generated by an experimental rig. Effect of different wind speeds on the whirling flame was studied by an oil pool of two different diameters. Lateral images of the whirling flame collected were analyzed. Results show that under cross flow, the whirling flame was deflected along the direction of incoming flow. With the increase in wind speed, the deflection angle increased gradually. The angle also increased with the increase in pool diameter. When the cross flow increased to a certain value, the flame stopped swirling, and changed to an irregular shape. The maximum cross wind speed of the flame that did not stop flame rotation decreased with diameter. Crosswind with lower speed would raise the temperature of the whirling flame. When the wind speed was higher than a critical value, the temperature was reduced because burning rate decreased.

Numerical simulation of the dust particles deposition on solar photovoltaic panels and its effect on power generation efficiency

The deposition of dust particles on the surface of solar photovoltaic panels leads to a decrease in power generation efficiency, so it is necessary to study the interaction mechanism between dust particles and solar photovoltaic panels. Aiming at the problem that the simplified two-dimensional model cannot reflect the actual photovoltaic power station in the traditional research, a geometric model of the distribution form of the 3 × 3 solar photovoltaic panel array is constructed. The shear stress transport k−ω turbulence model is used to predict the flow field changes around solar photovoltaic (PV). A discrete particle model is used to predict the particle deposition rate of photovoltaic panels. The effects of different wind speeds, particle sizes, and wind angles on particle deposition were analyzed. With the increase of wind speed, the deposition amount of the photovoltaic panels in the last two rows gradually decreased, while the photovoltaic panels in the first row showed a trend of first decreasing and then increasing. As the particle size increases, the particle deposition amount increases gradually. When the particle size is less than 60 μm, the deposition amount on the photovoltaic panel is less than 0.03g. When the particle size is greater than 60 μm, the deposition amount of particles increases exponentially. The maximum deposition amount is 3.98g, and the maximum deposition rate is 0.796% for 160 μm particles. Wind angle has different effects on the deposition on different rows of photovoltaic panels. When the wind Angle is 0°, the deposition amount of the first row of photovoltaic panels is the largest, the deposition amount is 4.66g, and the deposition rate is 0.932%. When the wind angle is 45°, the deposition amount on the second and third rows of photovoltaic panels is the largest, the deposition amount is 3.21g, and the deposition rate is 0.642%. Finally, the changes in the maximum output power of photovoltaic panels after 60 days of exposure were predicted using an improved dust particle occlusion model.

Experimental Investigation of Droplet Generation by Post-Breaking Plunger Waves

Understanding the droplet cloud and spray dynamics is important for the study of the ocean surface and marine boundary layer. The role that the wave energy and the type of wave breaking play in the resulting distribution and dynamics of droplets are yet to be understood. The aim of this work was to generate violent plunging breakers in the laboratory and analyze the spray production post-breaking, i.e. after the crest of the wave impacts in the free surface. The droplet sizes and their dynamics were measured with imaging techniques and the effect of different wind speeds on the droplet production was also considered. It was found that the mean radius increases with the wave energy content and the number of large droplets (radius > 1 mm) in the vertical direction increases with the presence of wind. Furthermore, the normalized distribution of droplet sizes is consistent with the distribution of ligament-mediated spray formation. Also, indications of turbulence affecting the droplet dynamics at wind speeds of 5 m/s were found. The amount of large droplets (radius > 1 mm) found in this work was larger than reported in field studies.

Wind Speed and Direction Drive Assisted Dispersal of Asian Citrus Psyllid.

Wind directly influences the spread of vector-borne plant pathogens by driving the passive dispersal of vectors to potentially new areas. Here, we evaluated the effect of wind speed and direction on the dispersal of the Asian citrus psyllid (ACP), Diaphorina citri (Kuwayama) (Hemiptera: Psyllidae), the vector of the bacteria causing huanglongbing (HLB), a lethal disease of citrus. The effect of different wind speeds on short or long-distance dispersal of ACP was investigated using a high-speed wind tunnel under laboratory conditions. The effect of wind direction on ACP dispersal under field conditions was evaluated using custom-made wind vane-style traps. In wind tunnel assays, ACP remained on plants until wind treatments reached ≥48 km/h when psyllids were mostly dislodged from plants and moved by the wind. For a short-distance, wind-driven movement (movement by the wind from one plant to another), the effect of wind speed was not significant at any of the wind speed treatments tested. Wind vane traps placed in a Florida citrus grove captured significantly more ACP on the windward side, suggesting that ACP were moved with the wind. The number of ACP found on the windward side of traps was significantly higher from May to August. These results indicate that ACP is likely to disperse with prevailing wind direction and that settled ACP may become dislodged and moved at random by high wind speeds occurring in areas of significant citrus production (southern California, Florida, or Texas).

Structural Design and Stress Analysis of a Helical Vertical Axis Wind Turbine Blade

In this study, a Computational Fluid Dynamics (CFD) model is designed to investigate the structural analysis of a helical Vertical Axis Wind Turbine (VAWT) blade which is using National Advisory Committee for Aeronautics (NACA) 0018 airfoil and numerical calculations are conducted by using Comsol Multiphysics. The main objective of this study is to determine that the strength of the turbine blade against bending caused by increased wind speeds is sufficient for the selected turbine blade material. This paper presents also an investigation of the effects of different wind speeds on the structure of a helical VAWT blade that is fixed to the support arm which is attached to the VAWT’s main shaft. In this study, a turbine blade which is placed in an air flow field is subjected to approaching strong wind with different velocities. The model solves for the flow around the blade and the structural displacement due to the fluid load. This investigation consists of two main parts: Solving for the fluid flow around the turbine blade with a free stream velocities of 1, 3, 5, 7, and 9 m/s, and Studying the deformation of the turbine blade caused by the fluid load. The risk of failure according to the von Mises criterion for the ductile materials such as aluminum is also investigated.

Effect of different wind speeds and sealed curing time on early-age shrinkage of cement paste

The influence of different wind speeds and sealed curing time on early-age shrinkage of cement paste was investigated. The 72-h early-age total shrinkage of cement paste after sealed curing for 0 h, 3 h, 6 h, 9 h, 12 h, and 24 h starting from the initial setting time under different wind speeds was studied. Water loss, autogenous shrinkage, tensile strength, pore size distribution (PSD) and hydration degree were measured. Elastic modulus, cracking strain, and radius of the pores where the meniscus forms were calculated based on the data obtained. For mixtures that did not undergo sealed curing, the wind speed could considerably increase the drying shrinkage and total shrinkage of the cement paste. The wind speed also reduced the early tensile strength, hydration degree, and elastic modulus of the cement paste. Within 1 day, the cracking strain was reduced by wind speed. According to the experimental data, a fitting formula for the early total shrinkage of cement paste is proposed, and the wind speed influencing factor βw is also proposed for the first time. Considering the PSD and water loss to study the mechanism of early drying shrinkage of cement paste, we found that there is a good correlation between rs and drying shrinkage. The exponential formula is given between rs and drying shrinkage. For mixtures with sealed curing, the total shrinkage and water loss decreased with increasing sealed curing time. However, the effects of water loss at different stages on drying shrinkage were different. Water evaporation in the early stage led to more drying shrinkage than water evaporation in the later stage. Sealed curing also weakened the increasing effect of wind speed on total shrinkage, so that at the same wind speed, the shrinkage increment was considerably reduced. After analysis and comparison, it was found that it is economical and reasonable to adopt sealed curing for 6 or 9 h, which can effectively decrease the early total shrinkage and improve the cracking strain of the cement paste in the wind environment.

Numerical simulation of toxic gas diffusion in confined space

In this paper, the numerical simulation method is used to study the gas diffusion in a limited space under the scene of poisonous gas attack or leakage. Based on the STAR-CCM + software, the toxic gas diffusion process in a limited enclosed space under specific flow field conditions was simulated and analyzed, and the effects of different wind speeds on the diffusion law and concentration field distribution were studied.

Brief communication: Wind-speed-independent actuator disk control for faster annual energy production calculations of wind farms using computational fluid dynamics

Abstract. A simple wind-speed-independent actuator disk control method is proposed that can be applied to speed up annual energy production calculations of wind farms using Reynolds-averaged Navier–Stokes simulations. The new control method allows the user to simulate the effect of different wind speeds in one simulation by scaling a calibrated thrust coefficient curve, while keeping the inflow constant. Since the global flow is not changed, only the local flow around the actuator disks need be recalculated from a previous converged result, which reduces the number of required iterations and computational effort by a factor of about 2–3.

Effect of wind speed on the size distribution of gel particles in the sea surface microlayer: insights from a wind–wave channel experiment

Abstract. Gel particles, such as transparent exopolymer particles (TEP) and Coomassie stainable particles (CSP), are important organic components in the sea surface microlayer (SML). Here, we present results on the effect of different wind speeds on the accumulation and size distribution of TEP and CSP during a wind wave channel experiment in the Aeolotron. Total areas of TEP (TEPSML) and CSP (CSPSML) in the surface microlayer were exponentially related to wind speed. At wind speeds < 6 m s−1, accumulation of TEPSML and CSPSML occurred, decreasing at wind speeds of > 8 m s−1. Wind speeds > 8 m s−1 also significantly altered the size distribution of TEPSML in the 2–16 µm size range towards smaller sizes. The response of the CSPSML size distribution to wind speed varied through time depending on the biogenic source of gels. Wind speeds > 8 m s−1 decreased the slope of CSPSML size distribution significantly in the absence of autotrophic growth. For the slopes of TEP and CSP size distribution in the bulk water, no significant difference was observed between high and low wind speeds. Changes in spectral slopes between high and low wind speed were higher for TEPSML than for CSPSML, indicating that the impact of wind speed on size distribution of gel particles in the SML may be more pronounced for TEP than for CSP, and that CSPSML are less prone to aggregation during the low wind speeds. Addition of an E. huxleyi culture resulted in a higher contribution of submicron gels (0.4–1 µm) in the SML at higher wind speed (> 6 m s−1), indicating that phytoplankton growth may potentially support the emission of submicron gels with sea spray aerosol.

Analysis of external dynamic loads influence to photovoltaic module structural performance

Abstract Efficiency of modern photovoltaic (PV) systems decreases significantly when the crystalline structure of PV modules is damaged due to climatic factors, such as wind and mechanically similar dynamic effects. General certifications of PV modules consist of only static tests (according to Photovoltaic standard IEC 61215 and IEC 61646), however in reality, PV modules are operating in a dynamic environment. The purpose of the article is to show that for the certification of PV modules the dynamic characteristics of PV modules must be accounted also. Nowadays PV modules are used in different dynamic objects like cars, boats etc., where dominant loads are of dynamic environment. This paper presents theoretic and experimental studies. For the investigation of dynamic loads acting on PV modules, a testing stand has been designed. PV modules were loaded with cyclic dynamic loads. During the experiment, the PV modules were loaded with external excitation, the excitation amplitude is not exceeding more than 7 mm. During the experiment, the PV modules were excited, in the frequency range of 0 to 40 Hz and the sweep generating mode was used. The aim of this excitation to simulate different weather conditions. Experimental and theoretical results showed the reaction of PV modules in different weather conditions (which means that the effect of different wind speeds is evaluated). The proposed assessment methodology can be applied successfully when designing PV modules and accounting for mechanical dynamic effects. In conclusion, it is not accurate and appropriate to evaluate the safety and stability of PV modules just through the existing static analysis in IEC 61215. The dynamic effects of the loading on PV module also need to be paid attention to. The attention needs to be paid to the dynamic effects of the loading on PV module.

A method of coupling CFD and energy balance simulations to study humidity control in unheated greenhouses

A coupling method is presented to study the night-time climate in greenhouses. The approach is based on two simulation methods: energy balance simulations (ES) and computational fluid dynamics (CFD). The coupled approach takes advantage of the strengths of each method and reduces their weaknesses. Two CFD parametric studies were carried out. The first one analysed the effects of different wind speeds and ventilator opening degrees on the ventilation rate. The second study assessed the effects of different sky temperatures and ventilator opening degrees on convective heat transfer coefficients. The CFD method was then coupled with the ES through the exchange of two variables: the CFD simulations provided the ventilation rates for the ES and the CFD method supplied the convective heat transfer coefficients used by for the ES. This coupling approach was applied to the study of night-time ventilation in an unheated, polyethylene-covered greenhouse where two important scenarios were addressed: clear-sky conditions and an overcast sky. Results from the two studies indicate that ventilation during the night-time in winter improves greenhouse climate; in the clear-sky case, relative humidity was reduced and the temperature was raised since ventilation reduced or eliminated thermal inversion, whereas in the covered-sky situation, ventilating reduced the humidity content, but the temperature dropped. As expected, the increases and drops in temperature and humidity also depended on external conditions. Minor opening angles produced the greatest changes in terms of greenhouse air temperature and relative humidity.

Simulation Analysis of Thermal Losses of Parabolic trough Solar Collector in Malaysia Using Computational Fluid Dynamics

The increase trend in fuel price coupled with escalating carbon dioxide concentration and energy security have encouraged the world to shift towards renewable energy sources. Parabolic trough collector is the most proven technology for indirect steam generation in solar thermal power plants. Since the annual average daily solar radiation for Malaysia are from 4.21 KWh/m2 to 5.56 KWh/m2 and sunshine duration is more than 2200 hours per year, parabolic trough solar collector is a very promising technology in the renewable energy field. The purpose of this paper is to simulate and describe the heat losses (radiation and convection) associated with heat collection element (HCE) of Solar Parabolic Trough Collector (PTC), the effect of different wind speeds and mass flowrate of the heat transfer fluid (HTF) on thermal losses were investigated. The receiver of the parabolic trough is modeled in CFD code ANSYS Fluent environment and the geometry is similar to that of LS-2 parabolic trough solar collector. Some assumptions have been made to ease and simplify the simulation. Solar radiation flux profile around the absorber tube is assumed uniform and the radiation flux is treated as heat flux wall boundary condition for the absorber tube. Heat loss model was simulated by employing the Surface – to – Surface (S2S) radiation model to account for the radiation exchange in an enclosure (vacuum annulus gap) of gray – diffuse surfaces. It resulted in a favorably low temperature of the glass envelope as compared to the temperature of the absorber. The convection and radiation heat loss to the surrounding was calculated by the resulting temperature of the glass envelope from the simulation model.

Risk and uncertainty analysis for dam overtopping – Case study: The Doroudzan Dam, Iran

There is a growing tendency to assess the safety levels of existing dams by using mathematical and statistical methods. In this study, the application of risk and uncertainty analysis to dam overtopping is presented for Doroudzan Reservoir located at the south part of Iran. The main objective of the overtopping analysis of dams is estimating the height of water in the reservoir under various inflows and comparing the computed results with the dam crest elevation. Hence, the main steps of this study include univariate flood frequency analysis of annual maximum inflows to estimate the peak flows in various return periods, generate inflow hydrographs based on the estimated peak flows, and route the hydrographs through the reservoir to compute the maximum height of the water in reservoir. In this study, the spillway discharge coefficient, quantile of peak flows, and initial water surface level are subject to uncertainty, and the Monte-Carlo simulation (MCS) and Latin hypercube sampling (LHS) are applied to perform the uncertainty analysis. In addition to inflows, the effect of different wind speeds on the probability of overtopping has been considered. The results demonstrated that both increasing water level and wind speed have significant impact on the risk of overflowing.

High‐speed imagery captures new sea spray formation mechanism

When strong winds blow over ocean waves, small droplets of sea spray rise into the air, enhancing the exchange of heat, mass, and energy between the air and the sea. How effective sea spray is at mediating each of these dynamics depends on the rate at which droplets are created and the drop size distribution of the mist. Unfortunately, research has been limited by a dearth of observational evidence that could explain the details of sea spray generation, including understanding the drop size distribution or the effects of different wind speeds. Previous research with high‐speed cameras aiming to capture the moment of drop formation was limited by camera resolutions too low to see all but the largest drops.

Analysis and Study on Centrifugal Rotating Speed Control of Small Wind Turbine Blade

Wind power is a clean renewable energy. It plays an important role in changing environmental condition and economic development. Wind turbine is a wind energy capture control. Rotating speed control of wind turbine blade is one key problem of wind power generator technology. Through analyzing the theory of centrifugal rotating speed control, this paper carried out the experiments on centrifugal rotating speed control device of small wind turbine blade, and analyzes the effects of different wind speeds on rotating angle of wind turbine blade. A method of rotating speed control has been mentioned. The experimental results and analysis have certain reference value for design and rotating speed control of wind turbine blade.

A pilot study on pollen representation of mountain valley vegetation in the central Alps

The relative pollen productivity (RPP) of Pinus cembra, Larix, Picea, Gramineae, and Cyperaceae was estimated for the Upper Engadine area, an inner-alpine sub-continental valley in SE Switzerland lying above 1800 m a.s.l. The influx of pollen originating from lowlands was assumed constant between the investigated sites and could thus be used to establish relative pollen accumulation rates (rPAR) as a basis for further calculations. Wind above the canopy was assumed as the major mode of pollen transport and the effect of different wind speeds was tested. In order to evaluate the results pollen percentage values were simulated and compared with the empirical data. The method is sufficiently accurate for evaluation of spatially-explicit vegetation models, although the low number of sites eludes robust statistical testing.

Optimal Control of an Aircraft-Towed Flexible Cable System

The control of an aerial-towed flexible cable system for precision rendezvous and snatch pickup of payloads is considered. In past studies of related systems, optimal trajectories have been determined assuming that the cable remains straight. However, aerodynamic drag and deployment forces can cause bowing of the cable that can significantly alter the position of the cable tip relative to the aircraft. To account for this, the cable is modeled using lumped masses connected via rigid links. Multiple rendezvous sequences using only cable winch control and including features such as collision avoidance and variable winds are solved by multiple-phase direct transcription methods. Numerical results show that for some multiple rendezvous scenarios it is necessary to use the cable lateral dynamics and swing motion to avoid impact with elevated terrain. The effect of different wind speeds and directions are also studied.

The Effects of Wind and Altitude in the 200-m Sprint

A mathematical model is used to determine the effect of wind resistance and altitude on 200-m race times. The model is used to simulate the effect of different wind speeds, wind directions, and lane allocation in the 200-m sprint. For the 200-m event there is a single wind gauge recording only the wind’s component velocity in the straight, and not the wind direction. For record purposes the wind reading should not exceed 2 m/s. It is evident that for the same official wind reading, an athlete may face vastly different conditions. The model estimates that for the same wind reading, the prevailing conditions can produce a time difference of as much as 0.5 s. Results indicate that many legal performances in the 200-m are currently ruled out for record purposes. Some performances which are officially wind-assisted have in fact been hindered by an overall head wind when it is averaged throughout the race. Conversely, some performances which are run into a head wind in the straight have benefited from an overall tail wind. We estimate that, on average, for a 2-m/s wind blowing down the straight, the 200-m runner benefits from an overall tail wind of only 0.95 m/s. The lower air density at an altitude of 1,500 meters produces an advantage of 0.11 s in the 200-m, which equates to a 2-m/s tail wind at sea level blowing directly down the straight. Correction estimates are provided for the combined effect of both wind and altitude in 200-m races. A new all-time world top five ranking list for men and women is produced for the 200-m event, corrected for wind and altitude effects.

Modulation of whitefly take‐off and flight orientation by wind speed and visual cues

AbstractThe effect of different wind speeds on take‐off and flight orientation of the sweetpotato whitefly, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae), was studied in the presence of a green visual stimulus which reflected 550 ± 10 nm light, or a white stimulus of the same intensity. When the white light was present, take‐off was negatively correlated with wind speed. Analysis of the flight tracks of whiteflies in 0, 15 and 30 cm/s wind with the white light present showed that flight was not directed toward the stimulus in zero wind, and that insects were carried downwind as the wind increased. Net displacement downwind was significantly slower than the wind speed, indicating that B. tabaci can control its rate of displacement relative to its surroundings, and is not always passively transported by the wind. In the presence of the green visual stimulus, take‐off and flight behaviour of B. tabaci was markedly different to that observed in the presence of the white light. Taking off was more likely and whiteflies made upwind orientated flights, landing on the illuminated section of the screen when it reflected green light. At all wind speeds tested, the mean ground speeds of B. tabaci were approximately 20 cm/s whether the insects were flying upwind or downwind. This uniformity of ground speed regardless of the changing effects of wind‐induced drift in different directions strongly suggests that whiteflies actively control their ground speed using visual flow fields in a manner similar to all other flying insects examined thus far.

Algorithm for atmospheric and glint corrections of satellite measurements of ocean pigment

An algorithm is developed to correct satellite measurements of ocean color for atmospheric and surface reflection effects. The algorithm depends on taking the difference between measured and tabulated radiances for deriving water‐leaving radiances. The tabulated radiances are related to the measured radiance where the water‐leaving radiance is negligible (670 nm). The tabulated radiances are calculated for rough surface reflection, polarization of the scattered light, and multiple scattering. The accuracy of the tables is discussed. The method is validated by simulating the effect of different wind speeds than that for which the lookup table is calculated, and aerosol models different from the maritime model for which the table is computed. The derived water‐leaving radiances are accurate enough to compute the pigment concentration with an error of less than ±15% for wind speeds of 6 and 10 m/s and an urban atmosphere with aerosol optical thickness of 0.20 at λ443 nm and decreasing to 0.10 at λ670 nm. The pigment accuracy is less for wind speeds less than 6 m/s and is about 30% for a model with aeolian dust. On the other hand, in a preliminary comparison with coastal zone color scanner (CZCS) measurements this algorithm and the CZCS operational algorithm produced values of pigment concentration in one image that agreed closely.