Secondary Wind Research Articles

ADAMA-II wind farm performance assessment in comparison to feasibility study

The objective of this paper was to assess the performance of the Adama-II Wind Farm in comparison to the feasibility study. Using 1-year mast data, the site potential was reassessed by WAsP software and the performance of wind turbine generators was assessed by 2 years of SCADA data. The obtained mean annual wind speed and power density were 7.75 m/s, and 462 W/m2 while in the feasibility study, 9.55 m/s, and 634.6 W/m2, which resulted in 18.8%, and 27.1% deviations respectively. The prevailing and secondary wind directions obtained were ENE and NE with 35.7% and 19.1% while, in the feasibility study, ENE with 36.5% and E with 17.3%. From the SCADA data, the Capacity factor, Annual Energy Production (AEP), and Availability of wind turbines were determined as 30.5%, 398 GWh, and 95.1%. The reasons for the deviation were difference in long-term correction data and weather conditions during study period.

A Comparative Performance Analysis of Counter-Rotating Dual-Rotor Wind Turbines with Speed-Adding Increasers

Increasing the efficiency of wind power conversion into electricity poses major challenges to researchers and developers of wind turbines, who are striving for new solutions that can ensure better use of local wind potential in terms of both feasibility and affordability. The paper proposes a novel concept of wind systems with counter-rotating wind rotors that can integrate either conventional or counter-rotating electric generators, by means of the same differential planetary speed increaser, aiming at providing a comparative analysis of the energy performance of counter-rotating wind turbines with counter-rotating vs. conventional electric generators. To this end, a generalized analytical model for angular speeds and torques has been developed, which can be customized for both system configurations. Three numerical simulation scenarios have been contrasted: (a) a scenario with identical wind rotors in both systems, (b) a scenario with the secondary wind rotors being identical in the two applications, but different from the primary rotors, and (c) a scenario with different secondary rotors in the two wind turbines. The results have shown that the wind systems with counter-rotating generator are more efficient and have a higher amplification ratio, compared to systems with conventional generators. In addition, the analyzed wind system with a counter-rotating generator displays better energy performance with low values for output power and ratio of input speeds, whereas the wind turbine with a conventional generator proves to be more efficient in the high-value range of the above-mentioned parameters.

The Unconventional Eyewall Replacement Cycle of Hurricane Ophelia (2005)

AbstractHurricane Ophelia (2005) underwent an unconventional eyewall replacement cycle (ERC) as it was a Category 1 storm located over cold sea surface temperatures near 23°C. The ERC was analyzed using airborne radar, flight-level, and dropsonde data collected during the Hurricane Rainband and Intensity Change Experiment (RAINEX) intensive observation period on 11 September 2005. Results showed that the spin-up of the secondary tangential wind maximum during the ERC can be attributed to the efficient convergence of absolute angular momentum by the mid-level inflow of Ophelia’s dominantly stratiform rainbands. This secondary tangential wind maximum strongly contributed to the azimuthal mean tangential wind field, which is conducive for increased low-level supergradient winds and corresponding outflow. The low-level supergradient forcing enhanced convergence to form a secondary eyewall. Ophelia provides a unique example of an ERC occurring in a weaker storm with predominantly stratiform rainbands, suggesting an important role of stratiform precipitation processes in the development of secondary eyewalls.

Azimuthal Variations of the Convective-scale Structure in a Simulated Tropical Cyclone Principal Rainband

Previous numerical simulations have focused mainly on the mesoscale structure of the principal rainband in tropical cyclones with a relatively coarse model resolution. In this study, the principal rainband was simulated in a semi-idealized experiment at a horizontal grid spacing of 1/9 km and its convective-scale structure was examined by comparing the convective elements of the simulated principal rainband with previous observational studies. It is found that the convective scale structure of the simulated principal rainband is well comparable to the observation. The azimuthal variations of the convective scale structure were examined by dividing the simulated principal rainband into the upwind, middle and downwind portions. Some new features are found in the simulated principal rainband. First, the overturning updraft contains small-scale rolls aligned along the inward side of the outward-leaning reflectivity tower in the middle portion. Second, the inner-edge downdraft is combined with a branch of inflow from the upper levels in middle and downwind portions, carrying upper-level dry air to the region between the overturning updrafts and eyewall, and the intrusion of the upper-level dry air further limits the altitude of the overturning updrafts in the middle and downwind portions of the principal rainband. Third, from the middle to downwind portions, the strength of the secondary horizontal wind maximum is gradually replaced by a low-level maximum of the tangential wind collocated with the low-level downdraft.

Outer Rainbands–Driven Secondary Eyewall Formation of Tropical Cyclones

Abstract Secondary eyewall formation (SEF) could be considered as the aggregation of a convective-ring coupling with a tangential wind maximum outside the primary eyewall of a tropical cyclone (TC). The dynamics of SEF are investigated using idealized simulations based on a set of triplet experiments, whose differences are only in the initial outer-core wind speed. The triplet experiments indicate that the unbalanced boundary layer (BL) process driven by outer rainbands (ORBs) is essential for the canonical SEF. The developments of a secondary tangential wind maximum and a secondary convective ring are governed by two different pathways, which are well coupled in the canonical SEF. Compared with inner/suppressed rainbands, the downwind stratiform sectors of ORBs drive significant stronger BL convergence at its radially inward side, which fastens up the SEF region and links the two pathways. In the wind-maximum formation pathway, the positive feedback among the BL convergence, supergradient force, and relative vorticity within the BL dominates the spinup of a secondary tangential wind maximum. In the convective-ring formation pathway, the BL convergence contributes to the ascending motion through the frictional-forced updraft and accelerated outflow associated with the supergradient force above the BL. Driven only by inner rainbands, the simulated vortex develops a fake SEF with only the secondary convective ring since the rainband-driven BL convergence is less enhanced and thus fails to maintain the BL positive feedback in the wind-maximum pathway. Therefore, only ORBs can promote the canonical SEF. It also infers that any environmental/physical conditions favorable for the development of ORBs will ultimately contribute to SEF.

Switching strategy of the low wind speed wind turbine based on real-time wind process prediction for the integration of wind power and EVs

Utilizing the secondary wind resources in cities and countryside is a significant way to promote wind power consumption and sustainable transportation. However, the probability of wind speed near the cut-in wind speed increases in such area and resulting in frequent on/off switches as well as large fatigue load of the wind turbine. To address these problems, this paper proposes a switching strategy of the low wind speed wind turbine based on real-time wind process prediction. First, the wavelet decomposition and neural network are employed to predict the time series of wind speed in a real-time manner. Second, based on the historical and predicted wind speed, the typical wind processes are extracted by using the x-means algorithm. Third, seven indexes are defined to quantify the characteristics of the wind process set before developing the corresponding switching strategy for each type of it. Data from NREL are used to validate the proposed models. The results show that, the proposed strategy increases the energy yield, reduces the number of wind turbine switches as well as the power fluctuation. Therefore, the proposed strategy is beneficial to both wind power projects development and electric vehicles charging.

Wing loading, not terminal velocity, is the best parameter to predict capacity of diaspores for secondary wind dispersal.

Lift-off velocity may be the most useful surrogate to measure the secondary dispersal capacity of diaspores. However, the most important diaspore attribute determining diaspore lift-off velocity is unclear. Furthermore, it is not known whether terminal velocity used to characterize the primary dispersal capacity of diaspores can also be used to predict their secondary wind dispersal capacity. Here, we investigate how diaspore attributes are related to lift-off velocity. Thirty-six species with diaspores differing in mass, shape index, projected area, wing loading, and terminal velocity were used in a wind tunnel to determine the relationship between diaspore attributes and lift-off velocity. We found that diaspore attributes largely explained the variation in lift-off velocity, and wing loading, not terminal velocity, was the best parameter for predicting lift-off velocity of diaspores during secondary wind dispersal. The relative importance of diaspore attributes in determining lift-off velocity was modified by both upwind and downwind slope directions and type of diaspore appendage. These findings allow us to predict diaspore dispersal behaviors using readily available diaspore functional attributes, and they indicate that wing loading is the best proxy for estimating the capacity for secondary dispersal by wind.

Wind collision and accretion simulations of the massive binary system HD 166734

ABSTRACTI have run hydrodynamic simulations that follow the colliding wind structure of the massive binary system HD 166734 along its binary orbit. I show that close to periastron passage the secondary wind is suppressed and the secondary accretes mass from the primary wind. The system consists of two blue supergiants with masses of $M_1 \approx 39.5 ~\rm {M_{\odot }}$ and $M_2 \approx 30.5 ~\rm {M_{\odot }}$, on an orbit of $P \simeq 34.538\, {\rm d}$ with an eccentricity of e ≈ 0.618. This close O–O binary with high eccentricity is observed through its orbit in X-rays, where it shows an unusually long minimum close to periastron passage. I use advanced simulations with wind acceleration and a prescription treatment of accretion and I simulate the entire orbit at high resolution, which captures the instabilities in the winds. I find that the colliding wind structure is unstable even at apastron. As the stars approach periastron passage, the secondary wind is quenched by the primary wind and the accretion on to the secondary begins. The accretion phase lasts for ${\simeq}12 \,{\rm d}$, and the amount of accreted mass obtained per cycle is $M_{\rm {acc}} \simeq 1.3 \times 10^{-8} \,{\rm M}_{\odot }$. The accretion phase can account for the observed decline in X-ray emission from the system.

Responses of secondary wind dispersal to environmental characteristics and diaspore morphology of seven Calligonum species

AbstractSecondary diaspore dispersal by wind, that is, wind‐driven movement along the ground surface (GS), is important for the structure and dynamics of plant populations and communities. However, how wind velocity (WV), GS, and diaspore morphology influence diaspore secondary dispersal by wind are unclear. We used a wind tunnel and video camera to measure the threshold of WV (TWV) and diaspore velocities (DV) of secondary diaspore dispersal. Diaspores of seven Calligonum species with different appendages (wings, bristles, membranous balloon, and wings + thorns) were used to determine the TWV and DV under variable wind speed (4, 6, 8, and 10 m s‐1) and four GSs (cement, sand, loam, and gravel). GS and diaspore morphological traits explained 37.1 and 18% of diaspore TWV, respectively. Meanwhile, WV, GS, and diaspore morphological traits explained 62.4, 13.6, and 3.2% of DV, respectively. An increasing trend was shown for TWV, and a decreasing trend was shown for DV in the order of cement, sand, loam, and gravel surfaces. Spherical and light diaspores had low TWV and high DV, whereas winged and heavy diaspores had high TWV and low DV. Our results indicated that adaptive features of diaspore appendages might be the result of selection for primary dispersal or secondary dispersal. The mechanism of diaspore secondary dispersal is important for understanding the recovery of degraded sand dunes and providing theoretical support for restoration practices.

Combustion Optimization Test of “W” Flame Furnace Based on Orthogonal Experimental Design

This paper focuses on the selection ideas, test methods, test results and analysis of a “W” type flame furnace combustion test program. Under the electrical load of 300MW, 250MW, 200MW and 150MW, the orthogonal test method is adopted to change the “furnace outlet oxygen amount”, “secondary wind and grading wind distribution mode”, “burning air opening degree”, “secondary damper combination method” and “heat load distribution” of the boiler so as to make clear about the impact of various operating conditions on boiler efficiency and NOx emission level, and summarize the optimal operation mode of the boiler. The combustion adjustment can improve the economic and environmental protection of the boiler under different working conditions, which provides data support for equipment safety, environmental protection and economic operation, and provides reference for boiler combustion optimization test research and combustion optimization of the same type of furnace.

Analysis of the origin, formation and development of sand ramps on the Eastern slopes of Shirkouh, Yazd, Central Iran

The purpose of this study is to examine the sand ramps in the margin of Ernan playa located in Yazd Province, central Iran. The region is marked with several sand ramps, many of which are not observable as they are buried under colluvial and alluvial sediments or dense vegetation. Field studies indicated at least 18 fairly large sand ramps in the region in the form of both climbing and falling dunes. These sand ramps were formed mostly in the past and are stable and inactive now. However, in some parts of the region in question, these landforms are still forming and developing. The results indicated that the sediment, especially those of the sand ramps on windward slopes, have large grains. Also, over 50 percent of the sediments generally have grains with a diameter of more than 1mm. The presence of such minerals as Alkali Feldspar, Plagioclase, Quartz, Biotite, Muscovite, Amphibole, and Apatite, respectively in terms of quantity and frequency, in the sand ramp sediments indicates that the origin of sand ramp sediments is the monzogranites of the eastern slope of Shirkouh Mountain with the same texture and frequency. The very fact that the above-mentioned minerals are intact, i.e. they have not been rounded or eroded, suggests that these sediments have not been displaced a lot. The study of the developing sand ramps proved that such structures form at the height of more than 2400m with two months of frost annually, over 100mm of precipitation (periglacier conditions), and granite outcrops. The reconstruction of the past climate conditions indicated that the temperature in the cold Quaternary glacial age was 13 degrees lower than present, with glacier and periglacier conditions dominating. Under such conditions, the region’s granites were extremely weathered, hence producing a large quantity of grain sediments. The surface run-offs or ice tongues drifted these sediments toward Lake Ernan (i.e. the present Ernan playa) and deposited them at its shoreline. After the lake and the main river dried up, southwest winds led the sediments of the lakeshore and the Tang-e-Chenar River upward to the top of the mountains, where sand ramps were, thus, formed. Due to the short formation duration and steady climate, no colluvial, alluvial material, or even soil (despite the large quantity of feldspars in the sand ramps) was traced amid the sediment layers of the sand ramps in the studied region. The only features traced there were slopes, alluvial debris and vegetation, indicating the dominance of warmer and moister climate as compared to the conditions at the time of formation. The directions of the past and developing sand ramps are similar but opposed to the prevailing and secondary wind of the region, indicating that it is the local winds which have formed those ramps.

Structure of the IBEX Ribbon from Distributed Sources

The Interstellar Boundary Explorer (IBEX) mission discovered the presence of a global structure in energetic neutral atom emissions from the outer heliosphere not predicted by any model – the IBEX “ribbon”. In the search for possible explanations, observations have pointed to a likely source from neutral atoms produced through charge-exchange with the outflowing solar wind. The secondary (neutral) solar wind then undergoes charge-exchange beyond the heliopause to produce the proton population that forms the ribbon. Here we study the plasma structure beyond the heliopause created from distributed secondary neutral atom sources. We provide a framework to analyze the IBEX ribbon taking into account distributed neutral atom sources within the local interstellar medium.

The influence of wind in secondary settling tanks for wastewater treatment-A computational fluid dynamics study. Part I: Circular secondary settling tanks.

Computational fluid dynamics model is used to understand the impact of wind on the performance of a secondary settling tank (SST) in a wastewater treatment plant (WWTP). Unlike most of the previous modeling studies which evaluated the wind effect on the settling tank in a water treatment plant, this study evaluates a circular SST in a WWTP at different current velocities and flow conditions. Performance indicators, such as effluent suspended solids and sludge blanket height, and three-dimensional hydrodynamics profiles are compared among different windy conditions and the calm condition and under different wind directions and flow conditions. The simulation results show that the existence of wind has strong negative impacts on the overall performance of the circular SST. The prediction of ESS is doubled in the circular SST under the mild wind condition. Moreover, the circular SST is more sensitive to the wind along the inlet port direction. PRACTITIONER POINTS: This is the first comparison of wind effects on a circular secondary settling tank Detailed computational fluid dynamics solution procedures to simulate a secondary settling tank Wind effects are investigated under multiple flow conditions, current velocities, and wind directions The performance of a circular secondary settling tank is very sensitive to the wind Wind along the inlet port direction has stronger negative impacts than it along 45° to the inlet direction.

A trade-off between primary and secondary seed dispersal by wind

The seeds of most plant species are dispersed by multiple mechanisms. Whether functional traits mediate positive correlations or negative correlations (trade-offs) between different dispersal mechanisms has important consequences for ecological and evolutionary dynamics. We investigate how traits affect wind-driven seed dispersal through the air and across the ground (primary and secondary wind dispersal, respectively). We hypothesized that primary and secondary wind dispersal were positively correlated because they should both decrease with the wing loading of seeds. We test this hypothesis with wind-tunnel experiments using different seed morphologies of Zygophyllum xanthoxylon (heterocarpous) and Calligonum species. We measured primary dispersal distance at varying wind speeds and release heights, and quantified secondary dispersal potential as the threshold wind speed for seed movement on four ground surfaces. Contrary to our expectation, we found a context-dependent trade-off between primary and secondary wind dispersal. The smoother the ground surface, the stronger this trade-off becomes. The trade-off results from a positive relationship between wing loading and the ratio of vertical to horizontal seed projection (v/h-ratio): an increasing v/h-ratio not only promotes secondary dispersal on smooth surfaces by increasing wind interception of seeds, but also decreases primary dispersal distance by increasing wing loading and terminal velocity of seeds. The trade-off contradicts the widespread assumption of a positive correlation between primary and secondary dispersal. A simple classification into poorly and well-dispersed seeds is thus not possible. The trade-off may affect dynamics of succession and the expansion of pioneer vegetation, while potentially slowing down evolutionary responses to selection on seed dispersal.

Simulating the response of the secondary star of Eta Carinae to mass accretion at periastron passage

We use high resolution 3D hydrodynamical simulations to quantify the amount of mass accreted onto the secondary star of the binary system Eta Carinae, exploring two sets of stellar masses that had been proposed for the system, the conventional mass model ($M_1=120 M_{\odot}$ and $M_2=30 M_{\odot}$) and the high mass model ($M_1=170 M_{\odot}$ and $M_2=80 M_{\odot}$). The system consists of two very massive stars in a highly eccentric orbit. Every cycle close to periastron passage the system experiences a spectroscopic event during which many lines change their appearance, accompanied by a decline in x-ray emission associated with the destruction wind collision structure and accretion of the primary wind onto the secondary. We take four different numerical approaches to simulate the response of the secondary wind to accretion. Each affects the mass loss rate of the secondary differently, and in turn determines the amount of accreted mass. The high mass model gives for most approaches much more accreted gas and a longer accretion phase. We find that the effective temperature of the secondary can be significantly reduced due to accretion. We also test different eccentricity values and a higher primary mass loss rate and find their effect on the duration of the spectroscopic event. We conclude that the high mass model is better compatible with the amount of accreted mass, $\approx 3 \times 10^{-6} M_{\odot}$, required for explaining the reduction in secondary ionization photons during the spectroscopic event and compatible with its observed duration.

Equivalent Modeling and Comprehensive Evaluation of Inertia Emulation Control Strategy for DFIG Wind Turbine Generator

With the increasing penetration of renewable energy in power grid, many inertia emulation control strategies have been proposed to provide extra support to the power grid in system disturbances. To explain the physical resemblance and relations among all kinds of inertia emulation strategies, a proper double-fed induction generator (DFIG) model is proposed based on equivalent electromotive force $\text{E}_{\boldsymbol{r}}^{\mathrm {eq}}$ and equivalent power angle $\delta _{\mathrm {eq}}$ . A co-simulation research platform is also designed based on a real-time digital simulator (RTDS) and GH Bladed simulation software, and the detailed comparisons are made in terms of inertia response performance, weak grid operation stability, secondary frequency drop, and wind tower fatigue load. Research results point out that different control schemes are similar in inertia response while virtual synchronous generator (VSG) control and inertial synchronization control (ISynC) can improve weak grid operation stability, the VSG strategy is also effective in reducing frequency secondary drop and wind tower fatigue load, and the combination of the VSG for RSC and the ISynC for GSC can achieve the best control performance in all evaluation indexes.

Time Dependence of the IBEX Ribbon and the Globally Distributed Energetic Neutral Atom Flux Using the First 9 Years of Observations

Abstract Observations from the Interstellar Boundary Explorer (IBEX) of energetic neutral atoms (ENAs) reveal two populations, those emitted from a narrow (∼20°–40°) ribbon that is centered on the local interstellar magnetic field, and a globally distributed flux (GDF) that is controlled by processes in the heliosheath. This is a third study utilizing a previously developed technique to separate ENA emissions in the ribbon from the GDF. In the first ribbon separation study, we analyzed the first year of IBEX data at the energies of 0.7 keV and above; the second study analyzed data down to 0.2 keV using the first five years of IBEX data. Here, we utilize the separation analysis from 0.7 keV and above to study time evolution in 3 year intervals over the first nine years of IBEX data. This study is the first to reveal the global time evolution of the GDF distinct from that of the IBEX ribbon. We show that the time evolution of the GDF within 40° of the upwind pressure maximum is driven by changes in the solar wind ram pressure through compression and rarefaction in the heliosheath. In contrast, the GDF is relatively stable in the region centered on the heliotail downwind with respect to the interstellar flow. The evolution of the IBEX ribbon is observed to have a time lag with respect to the upwind GDF evolution, likely due to the secondary (neutral) solar wind source. The time lag observed in the ribbon evolution is consistent with the generation of ions retained for several years beyond the heliopause. These observations lend further support to secondary solar wind models of the IBEX ribbon, but also require that there is a significant several year time lag for reneutralization of ions that form the IBEX ribbon. We use this study of the 9 year separation of the IBEX ribbon from the globally distributed flux to prepare for a formal IBEX data release of ribbon and globally distributed flux maps to the heliophysics community.

Radioecological situation on the territory of the Volga Region Department of Hydrometeorology and Environmental Monitoring in 2016

The environment quality is an extremely relevant question, including taking into account radio-ecological situation. The development of local agriculture should take into account various radiation parameters that determine the current radiation situation. In particular, it is necessary to do regular radioecological monitoring of environmental pollution of the Samara Region and adjacent territories on the main types of radiometric observations. The paper focuses on the reliable and rapid detection of radioactive contamination, assessment of the radiation situation with the help of radio-ecological control of natural environment components. In the paper on the basis of the Volga Region Department of Hydrometeorology and Environmental Monitoring data the authors assess the radiation situation in the settlements of Samara, Saratov, Orenburg, Penza and Ulyanovsk Regions. The paper contains values of aerosols -activity concentration in the surface layer of the atmosphere as well as the data of the average annual values in Samara and adjacent regions. According to the data of radioecological monitoring the level of total -activity of radioactive fallout from the atmosphere is shown. The maximum values of the total -activity concentration of the atmospheric surface layer aerosols were recorded in summer, which is due to the secondary wind dust rise from the contaminated areas. It was shown that the average annual value of the total -activity of aerosols according to the results of studies is within the normal limits. The paper also contains conclusions about the degree of danger of the atmosphere surface layer contamination by technogenic radionuclides.

Colliding stellar winds structure and X-ray emission

We investigate the structure and X-ray emission from the colliding stellar winds in massive star binaries. We find that the opening angle of the contact discontinuity (CD) is overestimated by several formulae in the literature at very small values of the wind momentum ratio. We find also that the shocks in the primary (dominant) and secondary winds flare by approx 20 degrees compared to the CD, and that the entire secondary wind is shocked when the wind momentum ratio < 0.02. Analytical expressions for the opening angles of the shocks, and the fraction of each wind that is shocked, are provided. We find that the X-ray luminosity scales with the wind momentum ratio, and that the spectrum softens slightly as the wind momentum ratio decreases.

Air impact pulverization–precise classification process to support ultraclean coal production

This research demonstrates a novel technique for achieving ultraclean coal production through the coupling of pulverization, classification, and separation of Taixi anthracite. Specifically, ultrafine pulverization techniques used in noncoal fields were newly applied to coal in this study. Taixi anthracite served as the subject material, and an air impact pulverization–precise classification process was designed and demonstrated. The effects of primary variables on process outcomes were investigated, and then, the process was optimized. In order of effect, the primary variables included pulverizing pressure, secondary wind pressure, classifier II rotational speed, and classifier I rotational speed. The classified products with ash content, particle size and classification precision cascade change can be obtained, ultimately, realizing the results of quality-upgrading of coal products. Under optimal process conditions of a 0.5-MPa pulverizing pressure, 0.10-MPa secondary wind pressure, 210-Hz classifier II rotational speed, and 230-Hz classifier I rotational speed, ultraclean coal with an ash content of 1.40% was produced. Ash content gradients for different product classifications were apparent, suggesting that the separation effect can be determined through precise classification. Numerical simulation results indicated that airflow kinetic energy transformation was the primary energy source facilitating pulverization. During impact pulverization, Taixi anthracite experienced selective, differentiated, and surface pulverization effects.