Hydrodynamic forces and moments on two identical ellipses performing an overtaking maneuver

Motivated by the hydrodynamic interactions of underwater vehicles and bio-inspired swimmers, we perform simulations of the two-dimensional flow past two identical rigid ellipses performing an overtaking maneuver. The ellipses have an aspect ratio of 6, the Reynolds number associated with the speed of the overtaken ellipse is 1500, and the overtaking ellipse reaches up to twice that speed. We analyze the effect of the relative velocity and lateral distance on the force and moment coefficients on both ellipses, both their transient evolution as well as their time-averaged values. We specifically analyze the lift forces to better understand any maneuvering corrections required to maintain the configuration, and the associated energetic cost compared to changes in the drag coefficient on both ellipses. The results are compared with the hydrodynamic interactions between stationary ellipses to further assess the effect of relative motion.