Icing simulation: A survey of computer models and experimental facilities

A survey of the current methods for simulation of the response of an aircraft or aircraft subsystem to an icing encounter is presented. The topics discussed include a computer code modeling of aircraft icing and performance degradation, an evaluation of experimental facility simulation capabilities, and ice protection system evaluation tests in simulated icing conditions. Current research focussed on upgrading simulation fidelity of both experimental and computational methods is discussed. The need for increased understanding of the physical processes governing ice accretion, ice shedding, and iced airfoil aerodynamics is examined

Numerical simulations of ice accretion on wind turbine blades: are performance losses due to ice shape or surface roughness?

Ice accretion on wind turbine blades causes both a change in the shape of its sections and an increase in surface roughness. These lead to degraded aerodynamic performances and lower power output. Here, a high-fidelity multi-step method is presented and applied to simulate a 3 h rime icing event on the National Renewable Energy Laboratory 5 MW wind turbine blade. Five sections belonging to the outer half of the blade were considered. Independent time steps were applied to each blade section to obtain detailed ice shapes. The roughness effect on airfoil performance was included in computational fluid dynamics simulations using an equivalent sand-grain approach. The aerodynamic coefficients of the iced sections were computed considering two different roughness heights and extensions along the blade surface. The power curve before and after the icing event was computed according to the Design Load Case 1.1 of the International Electrotechnical Commission. In the icing event under analysis, the decrease in power output strongly depended on wind speed and, in fact, tip speed ratio. Regarding the different roughness heights and extensions along the blade, power losses were qualitatively similar but significantly different in magnitude despite the well-developed ice shapes. It was found that extended roughness regions in the chordwise direction of the blade can become as detrimental as the ice shape itself

Ice Accretion Prediction on Wind Turbines and Consequent Power Losses

Ice accretion on wind turbine blades modifies the sectional profiles and causes alteration in the aerodynamic characteristic of the blades. The objective of this study is to determine performance losses on wind turbines due to the formation of ice in cold climate regions and mountainous areas where wind energy resources are found. In this study, the Blade Element Momentum method is employed together with an ice accretion prediction tool in order to estimate the ice build-up on wind turbine blades and the energy production for iced and clean blades. The predicted ice shapes of the various airfoil profiles are validated with the experimental data and it is shown that the tool developed is promising to be used in the prediction of power production losses of wind turbines

Experimental investigations on wind turbine icing physics and anti-/de-icing technology

Wind turbine icing has been found to cause a variety of problems to the safe and efficient operations of wind turbines. Ice accretion on turbine blades would result in decreasing lift and increasing drag, thereby, leading to power reduction. The annual power loss due to icing was found to be 20 ~ 50% at harsh sites. Ice accretion and irregular ice shedding during wind turbine operation would lead to load imbalances and excessive turbine vibrations, which may cause structural failures, especially when coupled with strong wind loads. Icing issues can also directly impact personnel safety due to falling and projected large ice chunks. By leveraging the Icing Research Tunnel of Iowa State University (ISU-IRT), a series of experimental investigations were conducted to investigate the dynamic ice accretion process over the surfaces of typical wind turbine blade models and to explore the effective and robust anti-/de-icing strategies for wind turbines icing mitigation. More specifically, a comprehensive experimental study was conducted to quantify the transient surface water transport behavior over the ice accreting surface of typical wind turbine blade models by using a Digital Image Projection (DIP) technique. The aerodynamic performance degradation of the turbine blade models was characterized in the course of the ice accreting process by using two sets of high-sensitive multi-axis force/moment systems and a digital Particle Image Velocimetry (PIV) system. A novel hybrid anti-icing strategy that combines minimized electro-heating near the turbine blade leading edge and bio-inspired icephobic coatings to cover the blade surface was proposed. In comparison to conventional thermal-based anti-/de-icing methods to brutally heat the entire blade surface, the proposed hybrid strategy was demonstrated to be able to prevent the ice formation and accretion over the surfaces of the wind turbine blades effectively with only ~10% of the required power consumption. In addition to conducting wind tunnel experiments, a field campaign was also conducted in a mountainous wind farm to investigate the ice-induced performance degradation of multi-megawatt wind turbines by correlating the acquired images of ice accretion over the rotating wind turbine blades with an unmanned aerial vehicle (UAV) with the turbine operational data recorded by wind turbine supervisory control and data acquisition (SCADA) systems. The new findings derived from the present studies would lead to a better understanding of the underlying physics pertinent to the wind turbine icing phenomena, which could be used to improve current ice accretion models for more accurate prediction of ice accretion on wind turbine blades as well as to develop innovative anti-/de-icing strategies for safer and more efficient operation of wind turbines in cold weathers

Forecast of icing events at a wind farm in Sweden

This paper introduces a method for identifying icing events using a physical icing model, driven by atmospheric data from the Weather Research and Forecasting (WRF) model, and applies it to a wind park in Sweden. Observed wind park icing events were identified by deviation from an idealized power curve and observed temperature. The events were modeled using a physical icing model with equations for both accretion and ablation mechanisms (iceBlade). The accretion model is based on the Makkonen model but was modified to make it applicable to the blades of a wind turbine rather than a static structure, and the ablation model is newly developed. The results from iceBlade are shown to outperform a 1-day persistence model and standard cylinder model in determining the times when any turbine in the wind park is being impacted by icing. The icing model was evaluated using inputs from simulations using nine different WRF physics parameterization combinations. The combination of the Thompson microphysics parameterization and version 2 of the Mellor-Yamada-Nakanishi-Niino PBL scheme was shown to perform best at this location. The distribution of cloud mass into the appropriate hydrometeor classes was found to be very important for forecasting the correct icing period. One concern with the iceBlade approach was the relatively high false alarm rates at the end of icing events due to the ice not being removed rapidly enough. © 2014 American Meteorological Society

Aeronautical engineering: A continuing bibliography with indexes (supplement 317)

This bibliography lists 224 reports, articles, and other documents introduced into the NASA scientific and technical information system in May 1995. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics