Performance Benefits for Frequency and Amplitude Control of Inline Swimmers*

Numerous studies of fish schooling have observed thrust and efficiency benefits for a leader-follower in-line formation when a fixed relative spacing is maintained and an optimal phase synchronization is chosen.  Here, we present new simulations considering the hydrodynamic effects of two different approaches of controlling the thrust and, therefore, relative spacing between leader-follower pitching foils: frequency and amplitude control. Although both approaches can control the thrust by varying the frequency/amplitude of the follower, the performance benefits received by the follower foil can differ due to alterations in vortex-body interactions. Frequency control leads to mismatched frequencies resulting in a constantly changing phasing between an impinging vortex and the follower’s motion leading to low performance benefits. Amplitude control preserves frequency matching between the leader and follower and the ability to tune the phase difference between the swimmers. It will be shown that since amplitude control is able to maintain a constant, favorable phase angle the follower can take advantage of the leader’s wake and experience greater performance benefits compared to frequency control. These findings aid in the design of formation control schemes of schooling bio-robots that derive hydrodynamic benefits from schooling interactions.

 

This work was supported by the Office of Naval Research under Program Director Dr. Robert Brizzolara on MURI grant number N00014-22-1-2616.