Insects in tethered and free flight: the impact of turbulent inflow

We present a series of high-resolution numerical simulations of a bumblebee interacting with fully developed turbulent inflow. We consider both tethered and free flight, the latter with all six degrees of freedom coupled to the Navier–Stokes equations. To this end we vary the characteristics of the turbulent inflow, either changing the turbulence intensity or the spectral distribution of turbulent kinetic energy. Modifying the turbulence intensity shows no significant impact on the cycle-averaged aerodynamical forces, moments and power, compared to laminar inflow conditions. The fluctuations of aerodynamic observables, however, significantly grow with increasing turbulence intensity. Changing the integral scale of turbulent perturbations, while keeping the turbulence intensity fixed, shows that the fluctuation level of forces and moments is significantly reduced if the integral scale is smaller than the wing length. Our study shows that the scale-dependent energy distribution in the surrounding turbulent flow is a relevant factor conditioning how flying insects control their body orientation.