Optimal stiffness distributions in propulsive plates with time-periodic stiffness

We study the optimal spatial stiffness distributions in flexible flat plates swimming in an inviscid and incompressible fluid including time-periodic stiffness variation. It has been shown previously that time-periodic stiffness can lead to dramatic improvements on the thrust performance of an oscillating propulsor. Our goal is to explore the spatio-temporal stiffness parameter space to find optimal distributions for propulsive thrust and efficiency. The optimal stiffness distribution for spatially only varying stiffness approaches a rigid plate with a torsional spring at its leading edge. We seek to compare the optimal spatio-temporal stiffness distributions with the optimal spatial distributions found in the literature. We also compare results found with a full two-dimensional fluid structure interaction solver.