AERODYNAMIC INTERFERENCE IN FULL HELICOPTER CONFIGURATIONS: VALIDATION USING THE HELINOVI DATABASE

Abstract

The present paper summarizes the results obtained during the validation phase of the aerodynamic computational tools performed in the framework of the European research project HeliNOVI and relative to the interactional phenomena arising on a full helicopter configuration. The activity was carried out by exploiting the experimental database produced during the wind tunnel test campaign of the project for a 40% Mach and dynamically scaled BO105 helicopter model. Seven test cases were performed. A climb, a descent and a level flight were chosen as baseline test cases aiming at highlighting the phenomenological differ-ences among three main helicopter flight conditions. The remaining four were dedicated to the analysis of possible tail rotor (TR) modifications in order to alleviate those interactional aspects responsible for high TR noise emissions. The experimental results indicate a low influence of the main rotor (MR) as source noise in 12° climb and 60m/s level flight whereas a predominance during the descent flight because of MR blade vortex interactions. Conversely, the TR noise represents the main source of noise especially in climb flight whereas is irrelevant during the descent flight. The modification of the TR operational characteristics is effective in reducing the interactional aspects and thus the noise emission. The numerical-experimental comparisons highlight the extreme complexity of the aerodynamic phenomena arising on a helicopter during flight. The numerical computations sometimes provide different predictions. It is a common opinion that they are motivated by the summation of the differences in the methodologies as well as trim procedures applied rather than by a specific reason only.