Évaluation numérique du transfert thermique sur le rotor Caradonna et Tung

Abstract

Aviation regulations prohibit aircraft from flying with surfaces contaminated by frost. The accretion of ice on aerodynamic surfaces degrades their performance. The helicopter is the most threatened by the risk of icing, since it operates at low altitudes where the weather conditions are more favorable to ice accretion. Helicopters equipped with anti-icing systems use heat to melt the ice formed on the affected surfaces, namely the blades. An evaluation of the heat transfer on the blades helps optimizing the anti-icing systems. The numerical simulation of helicopter rotor’s flow field is still one of the most challenging aerodynamics problems due to the rotating flow and the complex geometry of the helicopter. CFD numerical simulation comes as a major tool for the prediction of helicopter flow field. Various studie have been conducted to model the rotor’s flow. However, there are no thermal transfer studies on the rotor’s blades in the literature. This study aims at evaluating the heat transfer on the rotor’s blades of helicopters by means of CFD simulations. CFD is based on the resolution of a number of equations. The Navier-Stokes equations are solved in an unsteady waw. The Spalart-Allmaras model is used to model the turbulence induced by the rotation of the blades. The Sliding Mesh technique is used to model the rotation of the blades. The rotor studied is proposed by Caradonna and Tung. It is composed of two rectangular blades. The mesh is multizone. It is composed of a static zone modeling the physical domain and a dynamic zone containing the blades of the rotor. This technique makes it possible to model the rotor in hovering and forward flight condition. The open source code used in this study is SU2. The numerical simulation with SU2 of the Caradonna and Tung rotor succeeded to model the distribution of the pressure coefficient on the rotor blades in hover. A comparison with the literature made it possible to validate the flow. The shock waves formed on the blade are well simulated at the position denoted by litterateur. Next, the heat flux was calculated on the blades. The Frossling number was used to evaluate the heat transfer. In hovering flight, it was found that the heat transfer varies according to the span position. It is higher at blade’s tips. So the ice formed at the blade’s tip is grater then at the root. Then the rotor was simulated in forward flight condition. The Frossling number changes according to the azimuth angle in addition to span position in forward flight. At the same span position an advancing blade is characterized by a higher heat transfer than that of a retarding blade. Due to the high rotation speed of the blades, the variation of Frossling number with span position is more important.

Date	1 Jun 2020
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	François Morency (Supervisor)