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.

Icing has since long been identified as a serious issue in the aeronautical world. Ice build up, due to the presence of supercooled water droplets in clouds, leads to degradation of aerodynamic and/or air intake performances, among other undesirable consequences. Hence aircraft manufacturers must comply with certifications and regulations regarding flight safety in icing conditions. In order to do so, ice protection systems are used. Due to the multi-physical context within which these systems operate, numerical simulation can be a valuable asset. The present work deals with the numerical modelling of electro-thermal ice protection systems. It is built around the development of three modules. Two of them are dedicated to modelling heat transfer in the system and in the ice block. The other one models the mechanical behaviour of ice and fracture. Hence, the mechanical properties of atmospheric ice are reviewed in order to identify some mechanical parameters relevant to the fracture model. The fracture mechanics numerical method is used to investigate possible ice shedding mechanisms, that is to say the mechanisms leading to the detachement of ice, which are not yet well understood. The final goal of this work is to propose a completely coupled 2nd generation simulation methodology for electro-thermal ice protection systems. Hence the feasibility of a coupled thermal computation with ice shedding prediction based on the developed modules is shown. / Le givrage a depuis longtemps été identifié comme une problématique sérieuse dans le monde aéronautique.L’accrétion de givre, due à la présence de gouttelettes d’eau surfondue dans les nuages, dégrade les performances aérodynamiques et le rendement des entrées d’air parmi d’autres conséquences néfastes. Ainsi, les avionneurs sont sujets à des règles de certifications concernant la capacité à voler en conditions givrantes. Pour se faire, des systèmes de protection contre le givre sont utilisés. En raison de la complexité des phénomènes physiques mis en jeux, la simulation numérique constitue un atout lors de la phase de conception. Ce travail de thèse porte sur la modélisation et la simulation numérique des systèmes électrothermiques de protection contre le givre. Il s’articule autour de trois approches de modélisation, qui ont donné lieu au développement de trois modules. Deux d’entre eux sont dédiés à la simulation du transfert de chaleur dans le système et dans la glace (changement de phase). Le troisième est lié à la modélisation du comportement mécanique du givre atmosphérique avec fissuration. Ainsi, les propriétés mécaniques du givre atmosphérique sont revues de façon à pouvoir identifier les paramètres intervenant dans le modèle de fissuration. Ce modèle est ensuite utilisé pour étudier les mécanismes possibles de détachement du givre, qui ne sont à l’heure actuelle pas encore bien compris. Le but final de ce travail est de proposer une méthodologie de simulation couplée pour les systèmes électrothermiques de protection contre le givre. Ainsi, la faisabilité d’un calcul couplé thermique-fissuration avec prédiction de détachement de givre est présentée.