In hover, descent, and low-speed forward flight the vortices trailed from the main rotor blade tips can cause many detrimental effects associated with blade vortex interactions (e.g., high vibration and noise levels, large transient loads). Moreover, for a helicopter operating in ground effect the tip vortices can persist far downstream in the wake, which may lead to whiteout or brownout conditions. Therefore, experiments and CFD simulations were performed to investigate the ability to diffuse these tip vortices using model-scale centrifugal pumping rotor blades. In the current study, experimental and numerical investigations were combined to further increase the understanding of the modified vortex formation process, as well as to gain insight into the complex flow environment generated in the rotating channel inside the rotor blades. High-resolution particle image velocimetry was used to gain insight into the flow field generated during the initial vortex formation process. Furthermore, phase-averaged measurements were used to validate the numerical simulations. It was found that for early wake ages, spanwise blowing effectively diffused the tip vortex. The CFD simulations revealed flow details in the internal channel where experimental measurements were not possible, and it was found that the inlet geometry along with the rotor thrust level had a significant influence on the volume flow rate through the internal channel, which may ultimately affect tip vortex diffusion.     «

In hover, descent, and low-speed forward flight the vortices trailed from the main rotor blade tips can cause many detrimental effects associated with blade vortex interactions (e.g., high vibration and noise levels, large transient loads). Moreover, for a helicopter operating in ground effect the tip vortices can persist far downstream in the wake, which may lead to whiteout or brownout conditions. Therefore, experiments and CFD simulations were performed to investigate the ability to diffuse t...     »