Tight coupling of helicopter airframe including the influence of the gearbox

Until recently vibrations in helicopters could only be measured or anticipated with high levels of uncertainty. This changed when tools focused on coupling started to emerge offering to combine both state-of-the-art fluid and structural dynamics solutions. This enables to predict the fluid–structure-interactions in the design phase which is an invaluable addition to the engineer’s toolbox. The presented work shows the results of a tightly coupled CSD-CFD simulation of a helicopter in forward flight. The energy distribution across the modes is analyzed for a trimmed flight state. The aerodynamic origins of the excitation are investigated based on the pressure distribution and vortex visualization. The influence of the included gearbox is estimated by comparing the results from two different CSD models.