Scan Science and Technology
Contact Leading Edge Experts & Companies
The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Muhammad S. Virk – One of the best experts on this subject based on the ideXlab platform.
Atmospheric Ice Loading and its Impact on Natural Frequencies of Wind TurbinesWind Engineering, 2020Co-Authors: Abdel Salam Y. Alsabagh, Muhammad S. Virk, Yigeng Xu, Omar BadranAbstract:
Wind energy is a promising way in the middle of growing demand for clean energy in high north, where Atmospheric icing is a hazard for safe operations of wind turbines. In this research work, the vibrational effects due to Atmospheric Ice accretion on a multi megawatt large wind turbine are numerically investigated using a finite element based approach. Three different icing scenarios were addressed and accreted on-blade Ice mass was calculated analytically based upon ISO 95214 standards. Special attentions are given to the first natural frequency of the wind turbine blade and its interaction when the exciting frequency approaches the natural frequency of the wind turbine tower. Results show variations of natural frequencies due to different accreted icing loads scenarios, which may have different implications to the integrity of the structure.
Atmospheric Ice Accretion on Non-Rotating Circular Cylinder:The Journal of Computational Multiphase Flows, 2020Co-Authors: Muhammad S. VirkAbstract:
Numerical study of Atmospheric Ice accretion on a non-rotating circular cylinder was carried out at dry rime Ice conditions. To validate the numerical model, results were compared with the experimental data obtained from CIGELE Atmospheric icing research wind tunnel (CAIRWT). A good agreement was found between experimental and numerical results. Numerical study showed that selection of appropriate numerical model of Ice density and droplet size distribution is important, as these can significantly varies the simulated Ice growth. Parametric study at different air flow velocities and angles showed a significant change in Ice accretion on circular cylinder. This research work provides a useful base for further numerical investigation of Atmospheric Ice accretion on circular power network cables installed in the cold regions like arctic and alpine.
Relation Between Angle of Attack and Atmospheric Ice Accretion on Large Wind Turbine’s BladeWind Engineering, 2020Co-Authors: Muhammad S. Virk, Matthew C. Homola, Per Johan NicklassonAbstract:
A numerical study of wind turbine blade profile’s angle of attack variation on Atmospheric Ice accretion near the blade tip section was performed. Three dimensional computational fluid dynamics (CFD) based numerical analyses were carried out using NACA 64618 blade profile at five different angles of attack ranging from -5 to +7.5 degrees. Based upon the flow field calculations and the super cooled water droplet collision efficiency, the rate and shape of accreted Ice was simulated for both rime and glaze Ice conditions. The results show that Atmospheric icing is less severe at lower angles of attack, both in terms of local Ice mass and relative Ice thickness.
Paul J Demott – One of the best experts on this subject based on the ideXlab platform.
Observations of organic species and Atmospheric Ice formationGeophysical Research Letters, 2020Co-Authors: Daniel J. Cziczo, Paul J Demott, A. J. Prenni, Sonia M. Kreidenweis, Darrel Baumgardner, Sarah D Brooks, David S. Thomson, James C. Wilson, Daniel M. MurphyAbstract:
 Aerosol particles found in the lower confines of the atmosphere are typically internal mixtures of sulfate, inorganic salts, refractory components, and organic species. The effect these complex combinations have on cloud formation processes remains largely unknown. We have conducted two complementary studies on one important process, the homogeneous formation of Ice by small particles. In the first study the freezing of Atmospheric aerosol was induced using controlled temperature and humidity conditions. In the second study the chemical composition of the residue from Ice crystals in high altitude clouds was analyzed. Here we show that organic components do not partition equally to the Ice and aqueous phases. Instead, organic-rich particles preferentially remain unfrozen. These results suggest that emissions of organic species have the potential to influence aerosol-cold cloud interactions and climate.
characteristics of Atmospheric Ice nucleating particles associated with biomass burning in the us prescribed burns and wildfiresJournal of Geophysical Research, 2014Co-Authors: Christina S Mccluskey, Paul J Demott, A. J. Prenni, E J T Levin, G R Mcmeeking, Amy P Sullivan, Thomas C Hill, Shunsuke NakaoAbstract:
An improved understanding of Atmospheric Ice nucleating particles (INP), including sources and Atmospheric abundance, is needed to advance our understanding of aerosol-cloud-climate interactions. This study examines diverse biomass burning events to better constrain our understanding of how fires impact populations of INP. Sampling of prescribed burns and wildfires in Colorado and Georgia, U.S.A., revealed that biomass burning leads to the release of particles that are active as condensation/immersion freezing INP at temperatures from −32 to −12°C. During prescribed burning of wiregrass, up to 64% of INP collected during smoke-impacted periods were identified as soot particles via electron microscopy analyses. Other carbonaceous types and mineral-like particles dominated INP collected during wildfires of ponderosa pine forest in Colorado. Total measured nINP and the excess nINP associated with smoke-impacted periods were higher during two wildfires compared to the prescribed burns. Interferences from non-smoke sources of INP, including long-range transported mineral dust and local contributions of soils and plant materials lofted from the wildfires themselves, presented challenges in using the observations to develop a smoke-specific nINP parameterization. Nevertheless, these field observations suggest that biomass burning may serve as an important source of INP on a regional scale, particularly during time periods that lack other robust sources of INP such as long-range transported mineral dust.
predicting global Atmospheric Ice nuclei distributions and their impacts on climateProceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Paul J Demott, A. J. Prenni, Sonia M. Kreidenweis, C. H. Twohy, M. S. Richardson, T. Eidhammer, Markus D. Petters, D. C. RogersAbstract:
Knowledge of cloud and precipitation formation processes remains incomplete, yet global precipitation is predominantly produced by clouds containing the Ice phase. Ice first forms in clouds warmer than -36 °C on particles termed Ice nuclei. We combine observations from field studies over a 14-year period, from a variety of locations around the globe, to show that the concentrations of Ice nuclei active in mixed-phase cloud conditions can be related to temperature and the number concentrations of particles larger than 0.5 μm in diameter. This new relationship reduces unexplained variability in Ice nuclei concentrations at a given temperature from ∼103 to less than a factor of 10, with the remaining variability apparently due to variations in aerosol chemical composition or other factors. When implemented in a global climate model, the new parameterization strongly alters cloud liquid and Ice water distributions compared to the simple, temperature-only parameterizations currently widely used. The revised treatment indicates a global net cloud radiative forcing increase of ∼1 W m-2 for each order of magnitude increase in Ice nuclei concentrations, demonstrating the strong sensitivity of climate simulations to assumptions regarding the initiation of cloud glaciation.
Masoud Farzaneh – One of the best experts on this subject based on the ideXlab platform.
A contribution to the study of the compressive behavior of Atmospheric IceCold Regions Science and Technology, 2020Co-Authors: H. Farid, Masoud Farzaneh, Ali Saeidi, Fouad ErchiquiAbstract:
Abstract In the last decades, research on Atmospheric icing of structures such as power transmission lines has attracted much interest. Accumulation and the shedding of Atmospheric Ice from overhead transmission lines and ground wires may cause their rupture and tower collapses, leading to power outages. The present work concerns a study of the compressive strength of Atmospheric Ice, under different experimental conditions such as strain rate, temperature, and porosity. For this reason, Ice was accumulated in the closed loop wind tunnel at CIGELE (Industrial Chair on Atmospheric Icing of Power Network Equipment), under three temperatures (− 20, − 15 and − 5 °C). The wind speed inside the tunnel was set at 20 m/s in order to obtain a mean volume droplet diameter (MVD) of 40 μm and a liquid water content (LWC) of 2.5 g/m3. Each type of Ice was tested at the same temperature at which it had been accumulated. A tomographic analysis was carried out on a small specimen (cylinder of 1 cm diameter × 2 cm length) for each temperature in order to quantify the porosity and determine the grain size and their distribution. The obtained results show a strong dependence of the compressive strength on temperature, strain rate and porosity. The ductile–brittle transition was identified within a strain rate ranging between 10− 4 s− 1 and 10− 3 s− 1. It was found that compressive strength increases with decreasing temperature for deaerated Ice. However, for Atmospheric porous Ice, compressive strength increases until − 15 °C, then decreases for lower temperatures. Compressive strength of Atmospheric Ice is highly dependent on porosity, which is related to the amount, size and distribution of pores inside the Ice.
Flexural and low-cycle fatigue behavior of Atmospheric IceJournal of Materials Science, 2020Co-Authors: Majid Kermani, Masoud FarzanehAbstract:
Accretion of Atmospheric Ice on power transmission lines may have detrimental effects, sometimes with major socio-economical consequences. The mechanical behavior of this type of Ice as an important aspect in the understanding of that issue is still unclear. In the present study, more than 70 tests were conducted using cantilever beams under gradually increasing cyclic load to measure the bending strength of various types of Atmospheric Ice. Atmospheric Ice was accumulated in a closed-loop wind tunnel at −6, −10, and −20 °C, with a liquid water content of 2.5 g m−3. Ice samples accumulated at each temperature level were tested at the accumulation temperature, but the Ice accumulated at −10 °C was also tested at −3 and −20 °C. Compared to the bending strength results for Atmospheric Ice under static load, the Ice showed less resistance against fracture under cyclic load. It was also revealed that bending strength of Atmospheric Ice decreases with the test temperature. Another 60 samples of Atmospheric Ice were also tested under cyclic loads with constant amplitude. The tests revealed that the samples of Atmospheric Ice accumulated at −10 and −6 °C do not fail under stresses less than 1 MPa after 2000 cycles. At stress levels close to the bending strength of Atmospheric Ice, however, sometimes the specimen fails after a few hundred cycles. In comparison with the Ice accumulated at −10 and −6 °C, Atmospheric Ice accumulated at −20 °C fails at stresses less than its bending strength. This can be attributed to the colder test temperature and the presence of cavities and cracks in this Ice that reduce its bending strength during cyclic stresses.
Study of Insulator Flashovers caused by Atmospheric Ice Accumulation, 2020Co-Authors: Masoud Farzaneh, Issouf FofanaAbstract:
This paper summarizes the results of research recently carried out on the inception and propagation of electrical discharge on an Ice surface. Investigations on discharge inception were performed using a simplified physical model consisting of a rod- plane gap half submerged in Ice. Empirical models are proposed, based on elements derived from the inception parameter analysis, to account for corona streamer propagation velocity and inception voltage/field on an Ice surface. Furthermore, a dynamic model is proposed to predict flashover of Ice– covered insulators. Assuming arc behavior to be a time dependant impedance, it was possible to determine various arc characteristics, such as leakage current time histories and flashover voltage. The results indicate the feasib ility of icing severity assessment and flashover prediction, using the proposed model.