Ice accretion on wind turbines is a major problem in cold climates that reduces power generation and fatigues turbine components. Effective anti-icing and de-icing strategies to manage ice accretion require reliable local assessment of icing conditions and a measure of ice accretion rate on structures. Such sensors could be located on meteorological towers near wind farms or the nacelle of wind turbines. A new concept for the estimation of atmospheric ice accretion based on the measurement of capacitance and resistance change between two charged cylinders as ice accretes on the cylinders is introduced in this study. Numerical simulation of the electric field between the charged cylinders is used to investigate the dependence of the sensitivity of capacitance to the distance between the cylindrical probes and location of ice deposits. The numerical results are validated experimentally using aluminum probes and a set of acrylic cylindrical sleeves that fit over the probes to simulate icing with accurate geometries. A charged cylindrical probes system constructed based on the numerical results is described and evaluated under controlled rime and glaze icing conditions in the University of Manitoba Icing Wind Tunnel. Test results indicate ice builds up on the cylindrical probes and the measured capacitance increases while the resistance decreases. The change in measured capacitance change correlates well with the increase in the ice mass. Rime and glaze ice are distinguishable based on the rate of change of resistance with ice accretion. The numerical and experimental results provide a proof of concept of the charged cylindrical probes ice accretion measurement concept.

Ice accretion on wind turbines is a major problem in cold climates that reduces power generation and fatigues turbine components. Effective anti-icing and de-icing strategies to manage ice accretion require reliable local assessment of icing conditions and a measure of ice accretion rate on structures. Such sensors could be located on meteorological towers near wind farms or the nacelle of wind turbines. A new concept for the estimation of atmospheric ice accretion based on the measurement of capacitance and resistance change between two charged cylinders as ice accretes on the cylinders is introduced in this study. Numerical simulation of the electric field between the charged cylinders is used to investigate the dependence of the sensitivity of capacitance to the distance between the cylindrical probes and location of ice deposits. The numerical results are validated experimentally using aluminum probes and a set of acrylic cylindrical sleeves that fit over the probes to simulate icing with accurate geometries. A charged cylindrical probes system constructed based on the numerical results is described and evaluated under controlled rime and glaze icing conditions in the University of Manitoba Icing Wind Tunnel. Test results indicate ice builds up on the cylindrical probes and the measured capacitance increases while the resistance decreases. The change in measured capacitance change correlates well with the increase in the ice mass. Rime and glaze ice are distinguishable based on the rate of change of resistance with ice accretion. The numerical and experimental results provide a proof of concept of the charged cylindrical probes ice accretion measurement concept.

Modern helicopters, civilian and military alike, are expected to operate in all weather conditions. Ice accretion adversely affects the availability, affordability, safety and survivability. Availability of the vehicle may be compromised if the ice formation requires excessive torque to overcome the drag needed to operate the rotor. Affordability is affected by the power requirements and cost of ownership of the deicing systems needed to safely operate the vehicle. Equipment of the rotor blades with built-in heaters greatly increases the cost of the helicopter and places further demands on the engine. The safety of the vehicle is also compromised due to ice shedding events, and the onset of abrupt, unexpected stall phenomena attributable to ice formation. Given the importance of understanding the effects of icing on aircraft performance and certification, considerable work has been done on the development of analytical and empirical tools, accompanied by high quality wind tunnel and flight test data. In this work, numerical studies to improve ice growth modeling have been done by reducing limitations and empiricism inherent in existing ice accretion models. In order to overcome the weakness of Lagrangian approach in unsteady problem such as rotating blades, a water droplet solver based on 3-D Eulerian method is developed and integrated into existing CFD solver. Also, the differences between the industry standard ice accretion analyses such as LEWICE and the ice accretion models based on the extended Messinger model are investigated through a number of 2-D airfoil and 3-D rotor blade ice accretion studies. The developed ice accretion module based on 3-D Eulerian water droplet method and the extended Messinger model is also coupled with an existing empirical ice shedding model. A series of progressively challenging simulations have been carried out. These include ability of the solvers to model airloads over an airfoil with a prescribed/simulated ice shape, collection efficiency modeling, ice growth, ice shedding, de-icing modeling, and assessment of the degradation of airfoil or rotor performance associated with the ice formation. While these numerical simulation results are encouraging, much additional work remains in modeling detailed physics important to rotorcraft icing phenomena. Despite these difficulties, progress in assessing helicopter ice accretion has been made and tools for initial analyses have been developed.Modern helicopters, civilian and military alike, are expected to operate in all weather conditions. Ice accretion adversely affects the availability, affordability, safety and survivability. Availability of the vehicle may be compromised if the ice formation requires excessive torque to overcome the drag needed to operate the rotor. Affordability is affected by the power requirements and cost of ownership of the deicing systems needed to safely operate the vehicle. Equipment of the rotor blades with built-in heaters greatly increases the cost of the helicopter and places further demands on the engine. The safety of the vehicle is also compromised due to ice shedding events, and the onset of abrupt, unexpected stall phenomena attributable to ice formation. Given the importance of understanding the effects of icing on aircraft performance and certification, considerable work has been done on the development of analytical and empirical tools, accompanied by high quality wind tunnel and flight test data. In this work, numerical studies to improve ice growth modeling have been done by reducing limitations and empiricism inherent in existing ice accretion models. In order to overcome the weakness of Lagrangian approach in unsteady problem such as rotating blades, a water droplet solver based on 3-D Eulerian method is developed and integrated into existing CFD solver. Also, the differences between the industry standard ice accretion analyses such as LEWICE and the ice accretion models based on the extended Messinger model are investigated through a number of 2-D airfoil and 3-D rotor blade ice accretion studies. The developed ice accretion module based on 3-D Eulerian water droplet method and the extended Messinger model is also coupled with an existing empirical ice shedding model. A series of progressively challenging simulations have been carried out. These include ability of the solvers to model airloads over an airfoil with a prescribed/simulated ice shape, collection efficiency modeling, ice growth, ice shedding, de-icing modeling, and assessment of the degradation of airfoil or rotor performance associated with the ice formation. While these numerical simulation results are encouraging, much additional work remains in modeling detailed physics important to rotorcraft icing phenomena. Despite these difficulties, progress in assessing helicopter ice accretion has been made and tools for initial analyses have been developed.

No description available.

No description available.

Ice growth may rapidly degrade the aerodynamic performance of an aircraft. It can also severely damage structures such as communication towers or power lines. Subsequently, de-icing and anti-icing systems have been developed and a number of codes designed to predict ice shapes. When ice accretion starts, two different types of ice can appear, depending on the temperature and conditions. All of the incoming fluid may freeze almost instantaneously and turn into rime ice. Alternatively, a fraction of the incoming fluid may freeze and turn into glaze ice while the other part remains liquid and may flow over the ice. Previous work on ice accretion has mainly targeted the ice shape and neglected the owing water layer. The present study focuses on this. A set of governing equations is derived for both rime ice growth and coupled ice growth and water flow. When rime ice accretes, a mass balance is used to calculate the shape. In the presence of both ice and water, the ice growth is governed by an energy balance and the water flow by a mass balance. These equations are solved numerically for the water flow alone and the coupled ice growth and water flow for two- and three-dimensional at inclined planes. The behaviour of both ice and water is studied. The model is then extended to deal with arbitrary substrates and solutions are sought for industrially important applications such as ice accretion on power lines or aerofoils. This research work forms part of the ICECREMO project. ICECREMO is a three-dimensional ice accretion and water flow code developed collaboratively by DERA, British Aerospace, Rolls Royce, GKN Westlands Helicopters and Cranfield University under the auspices of the UK department of Trade and Industry.

No description available.

Atmospheric icing is a major design factor for guyed lattice masts and transmission lines in Canada and many others countries with cold climate. Tall and slender guyed lattice towers are particularly sensitive to ice accretion, wind or combination of both, as they are often located in remote areas, where meteorological data are limited. The variation of local topography and seasonal climate affects icing conditions and complicates standardization of icing accretion design guidelines. Icing design criteria was evaluated in this study through an extensive literature review of current design standards for latticed structures subjected to ice and wind load and/or a combination of both, field and laboratory work.

Atmospheric icing is a major design factor for guyed lattice masts and transmission lines in Canada and many others countries with cold climate. Tall and slender guyed lattice towers are particularly sensitive to ice accretion, wind or combination of both, as they are often located in remote areas, where meteorological data are limited. The variation of local topography and seasonal climate affects icing conditions and complicates standardization of icing accretion design guidelines. Icing design criteria was evaluated in this study through an extensive literature review of current design standards for latticed structures subjected to ice and wind load and/or a combination of both, field and laboratory work.

No description available.