The Experts below are selected from a list of 9888 Experts worldwide ranked by ideXlab platform
Yang Liu - One of the best experts on this subject based on the ideXlab platform.
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an experimental investigation on the dynamic glaze ice accretion process over a wind turbine Airfoil Surface
International Journal of Heat and Mass Transfer, 2020Co-Authors: Linyue Gao, Yang LiuAbstract:Abstract Icing events, particularly under precipitation-icing conditions in which high-liquidity glaze ice tends to form, could pose significant threats to the safe and effective operations of wind turbines in cold and wet environments. During the glaze ice accretion process, the wind-driven unfrozen water was coupled with the growth of ice structures and difficult to be quantified and characterized. In the present study, we introduced a Digital Image Projection (DIP) technique to quantitatively measure the unsteady water runback behaviors and dynamic ice accretion process under typical glaze icing conditions over a highly-cambered wind turbine Airfoil Surface, i.e., the pressure-side Surface of DU91-W2-250 Airfoil, in the Icing Research Tunnel at Iowa State University (ISU-IRT). DIP measurement results were found to be able to successfully capture the time-resolved three-dimensional information of the water transport behaviors over the ice accreting Surface of the Airfoil model during the glaze icing processes. The stumbling motions of the rivulet flows were observed during the icing processes, coupled with an increasing fluctuations induced by the underneath ice roughness. The forces acting on the rivulet flows were analyzed, and a theoretical model based on the force balance was built to predict the rivulet flows. The effects of the incoming airflow velocity on the glaze icing process over the Airfoil Surface were also studied, and it was found that, as the incoming flow velocity increased, the runback rivulet flows would move farther downstream and became thinner and narrower due to the increased aerodynamic stress acting on them. The rivulet bulged shape was found to have an inverse relationship with the inflow velocity squared. In addition, the ice accreted over the Airfoil Surface during an icing process was quantitatively decoupled from the unfrozen wind-driven water, and the quantitative results can be used to validate and optimize current ice accretion models.
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an experimental investigation on the dynamic ice accretion and unsteady heat transfer over an Airfoil Surface with embedded initial ice roughness
International Journal of Heat and Mass Transfer, 2020Co-Authors: Kai Zhang, Yang Liu, Wei TianAbstract:Abstract In the present study, a comprehensive experimental study was conducted to evaluate the effects of initial ice roughness formed around the leading-edge of an Airfoil model on the dynamic ice accretion and unsteady heat transfer processes over the Airfoil Surface. The experimental study was performed in the Icing Research Tunnel at Iowa State University, Two Airfoil models with the same Airfoil shape were manufactured by using a rapid protype machine for a comparative study, i.e., one test model was designed to have embedded initial ice roughness around the Airfoil leading-edge and the other model having smooth Airfoil leading-edge as the comparison baseline. During the experiments, while a high-speed imaging system was used to record the early-stage icing morphologies over the Airfoil Surfaces with and without the initial leading-edge roughness, an infrared (IR) thermal imaging system was also utilized to map the corresponding Surface temperature distributions over the Airfoil Surfaces to quantify the unsteady heat transfer and dynamic icing, i.e., phase changing, processes under different test conditions. It was found that, the initial ice roughness formed around the Airfoil leading-edge would affect the characteristics of local airflow, impingement of supercooled water droplets, collection and transport of impacted water mass, unsteady heat transfer and subsequent ice accretion processes dramatically. The initial ice roughness formed around the Airfoil leading-edge would redistribute the impacted water mass, with more impacted water mass being captured and frozen over the roughness region. In addition, the initial ice roughness was also found to produce span-wise-alternating low- and high-momentum pathways (LMPs and HMPs, respectively), which can significantly affect the convective heat transfer and subsequent ice accretion processes over the Airfoil Surface.
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an experimental investigation of dynamic ice accretion process on a wind turbine Airfoil model considering various icing conditions
International Journal of Heat and Mass Transfer, 2019Co-Authors: Linyue Gao, Yang LiuAbstract:Abstract In the present study, the dynamic ice accretion process over a typical wind turbine Airfoil model (i.e., DU96-W-180 Airfoil) was experimentally investigated under various icing conditions. The experimental study was conducted in the Icing Research Tunnel of Iowa State University (i.e., ISU-IRT). Different icing conditions (i.e., rime, mixed and glaze) that wind turbine may experience in winter were reproduced by manipulating the airflow temperature, velocity, and liquid water content (LWC) in ISU-IRT. While a high-speed imaging system was used to reveal the dynamic ice accretion process over the Surface of the test model, an infrared (IR) thermal imaging system was used to map the corresponding temperature distributions over the ice accreting Airfoil Surface. Time variations of the ice thickness accreted along the leading edge (LE) of the test model were extracted based on the acquired high-resolution images of the ice accretion process under different test conditions. It was found that, due to the obvious runback of the impacted water (i.e., formation of water film and rivulets) over the Airfoil Surface, the growth rate of the ice layer accreted along the Airfoil leading edge was much slower under the glaze icing condition, in comparison with those under the rime and mixed icing conditions. Such Surface water transport behavior was also found to expand the ice influencing region. From the temperature evolutions during the dynamic icing processes, the transient processes of droplet impingement, water film/rivulets formation, and ice roughness growth were temporally resolved, providing comprehensive details of the unsteady heat transfer during the dynamic icing process. While the Surface temperature increment due to the direct droplet impingement was found to decrease monotonously along the chord in rime case, a stream-wise ‘plateau’ region was observed in the glaze and mixed icing cases due to the complex multiphase mass/heat transfer associated with the Surface water transport behaviors.
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A comparison study on the thermal effects in DBD plasma actuation and electrical heating for aircraft icing mitigation
International Journal of Heat and Mass Transfer, 2018Co-Authors: Yang Liu, Cem KolbakirAbstract:Abstract A comparison study of a novel method of utilizing thermal effects induced by Dielectric-Barrier-Discharge (DBD) plasma actuation (i.e., DBD plasma-based method) and a conventional electrical heating method for aircraft icing mitigation was performed in an Icing Research Tunnel available at Iowa State University (i.e., ISU-IRT). A NACA0012 Airfoil/wing model embedded with an AC-DBD plasma actuator and a conventional electrical film heater over the Airfoil Surface was tested under a typical aircraft icing condition. While a high-speed imaging system was used to record the dynamic ice accretion and transient Surface water transport processes over the Airfoil Surface, an infrared (IR) thermal imaging system was also utilized to map the corresponding Surface temperature distributions over the Airfoil Surface simultaneously to quantify the unsteady heat transfer and phase changing process over the ice accreting Airfoil Surface. It was found that, with the same power input, the DBD plasma-based method showed at least equivalent effectiveness, if not better, in preventing ice accretion over the Airfoil Surface, in comparison to the conventional electrical heating method. Further optimization of the DBD plasma-based method with a duty-cycle modulation was found to have a much better anti-/de-icing performance, in comparison to the conventional electrical heating method. The findings derived from the present study demonstrated the potential of a new class of anti-/de-icing strategy by leveraging the thermal effects induced by DBD plasma actuation for aircraft in-flight icing mitigation.
Adrian Ilinca - One of the best experts on this subject based on the ideXlab platform.
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heat and mass transfer during ice accretion on aircraft wings with an improved roughness model
International Journal of Thermal Sciences, 2006Co-Authors: Guy Fortin, Jean Louis Laforte, Adrian IlincaAbstract:This paper presents the thermodynamic model used in the numerical simulation of ice accreted on an Airfoil Surface in wet and dry regimes developed at AMIL (Anti-Icing Materials International Laboratory), in a joint project with CIRA (Italian Aerospace Research Center). The thermodynamic model combines mass and heat balance equations to an analytical representation of water states over the Airfoil to calculate the Surface roughness and masses of remaining, runback, and shedding liquid water. The water state on the Surface is represented in the form of beads, film or rivulets, each situation corresponding to a particular roughness height which has a major impact on the heat transfer coefficients necessary for the heat and mass balances. The model has been tested for severe icing conditions at six different temperatures corresponding to dry, mixed and wet accretion. Water mass, roughness and heat transfer convection coefficients over the Airfoil Surface are presented. The thermodynamic model combined with an air flow, water trajectory, and geometric model provides accurate results. It generates the complex ice shapes observed on the wing profile, and the numerical ice shapes profiles agree well with those obtained in wind tunnel experiments.
Mohammad Asid Zullah - One of the best experts on this subject based on the ideXlab platform.
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design of a low reynolds number Airfoil for small horizontal axis wind turbines
Renewable Energy, 2012Co-Authors: Ronit K Singh, Rafiuddin M Ahmed, Mohammad Asid ZullahAbstract:A low Reynolds number Airfoil was designed for applications in small horizontal axis wind turbines to achieve better startup and low wind speed performances. Experiments were performed on the improved Airfoil (AF300) in an open circuit wind tunnel at Reynolds numbers of 38,000, 75,000, 128,000 and 205,000. Pressure distributions were obtained over the Surface of the Airfoil and the lift and drag forces were measured with a dynamometer at different angles of attack, α. A CFD analysis was also performed to get additional information on the flow characteristics. Particle Image Velocimetry (PIV) together with smoke flow visualization were used to study the flow around the Airfoil. At the Reynolds numbers of 75,000, 128,000 and 205,000, maximum lift coefficients of 1.72, 1.81 and 1.86 respectively were obtained at the stall angle of 14°. The lift coefficient increased from 0.41 to 1.05 at Re = 38,000 in the α range of 0–18°, in which no stalling was documented. The results from PIV and smoke flow visualization showed that the flow stayed fully attached to the Airfoil Surface from Re as low as 56,000 at an angle of attack of 8° and maintained a fully attached flow up to 14° angle of attack for Re as low as 75,000.
Sergio Montelpare - One of the best experts on this subject based on the ideXlab platform.
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a quantitative ir thermographic method to study the laminar separation bubble phenomenon
International Journal of Thermal Sciences, 2005Co-Authors: R Ricci, Sergio MontelpareAbstract:Abstract The boundary layer separation phenomena are present in many application fields: for example the sailplanes, the micro-vehicles, the small wind turbines, the airplanes and the cars. On aerodynamic bodies operating at low Reynolds numbers, lesser than one million, it may happen a boundary layer local separation defined as: laminar separation bubble. This phenomenon induces a body drag increase and an eventual lift decrease; in some situations the cyclical bubble formation and detachment may induce pressure pulses and consequent vibration phenomena. In a previous research work [Internat. J. Thermal Sci. 43 (2004) 315] was verified the possibility to show qualitatively the presence of a laminar bubble by means of a thermographic observation of the body Surface. In this work is verified the possibility to carry out a quantitative study of the laminar bubble phenomenon by using the same IR technique. Three characteristic points of the bubble are particularly studied: the laminar separation point, the transition point and the turbulent reattachment point. The laminar bubble behaviour is analysed on a RR3823HL Airfoil by varying the angle of attack and the Reynolds number; the adimensional Stanton number, based on the Airfoil chord, is obtained in order to individuate the requested points in a more simple and objective way. This adimensional number is carried out by means of a finite numerical difference approach that makes a balance among the heat fluxes on the Airfoil Surface.
Guy Fortin - One of the best experts on this subject based on the ideXlab platform.
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heat and mass transfer during ice accretion on aircraft wings with an improved roughness model
International Journal of Thermal Sciences, 2006Co-Authors: Guy Fortin, Jean Louis Laforte, Adrian IlincaAbstract:This paper presents the thermodynamic model used in the numerical simulation of ice accreted on an Airfoil Surface in wet and dry regimes developed at AMIL (Anti-Icing Materials International Laboratory), in a joint project with CIRA (Italian Aerospace Research Center). The thermodynamic model combines mass and heat balance equations to an analytical representation of water states over the Airfoil to calculate the Surface roughness and masses of remaining, runback, and shedding liquid water. The water state on the Surface is represented in the form of beads, film or rivulets, each situation corresponding to a particular roughness height which has a major impact on the heat transfer coefficients necessary for the heat and mass balances. The model has been tested for severe icing conditions at six different temperatures corresponding to dry, mixed and wet accretion. Water mass, roughness and heat transfer convection coefficients over the Airfoil Surface are presented. The thermodynamic model combined with an air flow, water trajectory, and geometric model provides accurate results. It generates the complex ice shapes observed on the wing profile, and the numerical ice shapes profiles agree well with those obtained in wind tunnel experiments.