Flowtaxis in the wakes of oscillating airfoils

Many aquatic organisms from copepods to harbor seals are able to detect and respond to flow disturbances. The physiological mechanisms underlying such behavior remain a challenge for current and future research. Here, we propose a simplified flow sensing scenario in which a mobile sensor reorients its heading in response to local flow stimuli, with the goal of tracing the wakes created by oscillating airfoils to their source. Specifically, we engineer a feedback control strategy where the sensory measurements are based on transverse vorticity gradients. Through numerical experiments, we assess the efficacy of the sensor in following topologically distinct wakes. We demonstrate that the strategy is robust to variations in the wake itself, and we arrive at empirical rules that the sensor’s initial position and orientation must satisfy in order to successfully locate the airfoil. We conclude by commenting on the relevance of the model and results to animal behavior and bio-inspired underwater robotics. We also discuss current and future opportunities for employing machine learning tools to devise and improve these sensory control strategies.