Meeting Abstract
Flying animals regularly traverse complex landscapes characterized by dynamic, turbulent airflows. Despite longstanding interest in the mechanics of insect flight, recent studies have just begun to shed light on the effects of flow variation on flight performance. Most of these studies have focused on discrete flow perturbations or unsteady, structured flow such as Von Karman vortex streets. Wind in natural environments, however, is often characterized by isotropic turbulence containing flow variation across a range of spatial and temporal scales. Here, we present results from free flight experiments in bumblebees (Bombus impatiens) ranging from 95-200 mg flying in a wind tunnel across flow conditions. Body and wing dynamics were quantified for bees flying through each of five flow regimes: still air, low (1.5 m/s), and high (3.0 m/s) speed flow in both turbulent and laminar conditions. Turbulence was created with a square grid placed upstream of the wind tunnel working section, which created near-isotropic turbulence with an intensity (SD/mean) of ~15%, while laminar flow had a turbulence intensity of less than 1%. Variance in both body and wing kinematics increased in turbulent flows. In addition, wingbeat frequency in turbulence appears to increase relative to laminar flow at high (but not low) wind speeds, supporting previous findings in structured, unsteady flow. Finally, we examine the effect of body size on flight stability, as well as kinematic strategies for controlling body orientation and position in response to variable flow. Overall, these results demonstrate the challenges that face insects flying through variable flow and reveal the robust flight strategies necessary for successful navigation in natural aerial environments.
