Factors Affecting Rotor Stall Computation by Comprehensive Rotor Codes

Abstract

Comprehensive codes are the working horse for simulation purposes of a helicopter and its rotor under steady and unsteady conditions and they are also used to predict the operational limits until rotor stall. These limits are always dictated by aerodynamics - mainly flow separation due to airfoil stall - if not reached by other limits before. Accurate prediction of airfoil stall on rotating blades is a major challenge for comprehensive codes, despite many efforts spent on unsteady airfoil models. This paper focuses on hov-ering and high-speed rotor stall limits and on the factors that affect the rotor limits prediction.