Study on the effects of blade crossover on the blade airloads

Blade crossover, a periodic interaction between two blades rotating in opposite directions, is commonly observed in urban air mobility aerial vehicles with counter-rotating coaxial rotor configurations. These interactions lead to increased vehicle vibrations and alterations to the vehicle's acoustic signature. However, the underlying physics of these interactions are not well understood. This work aims to study the effects of blade crossover on blade airloads and understand the underlying physics. A towing tank facility was developed, enabling the translation of two infinite wings in opposite directions. Each blade was mounted with multi-axis strain gauge load cells to measure the blade airloads. Quantification of the temporal scale (ratio of blade chord to translation velocity) for the current problem shows that the time scale is always constant and implies that the airloads should exhibit self-similar characteristics. The validity of this observation is currently being explored by conducting experiments at different translation speeds and blade chord lengths. This parametric space provided insights into varying length and time scale effects on the airload characteristics during the blade crossover. Initial results show that the airload characteristics are independent of the translation speed exhibiting self-similar characteristics. Further analysis of the airloads self-similarity characteristics across different length scales will be presented.