We explore a simple (toy) model of undulating finite-length filaments swimming in viscous fluids, based on resistive force theory. The filaments are actuated by traveling waves, and we consider four different strategies: two smooth waveforms (cartesian and curvature sine waves) and two others with kinks (sawtooth and square waves). Analytical results in the limit of short filaments and/or small actuation parameters are provided. A new efficiency metric is proposed which takes into account that work expenditure is minimal when power consumption is maintained constant. This metric is particularly well-suited for short undulating filaments where power fluctuations for constant actuation rates can be substantial. Parametric studies are performed for a range of filament lengths and actuation parameters for the purpose of side-by-side comparisons. We give analytical expressions for swimming of arbitrary length filaments where the actuation is small. We describe “swimming resonances,” which are local maxima in performance that occur for certain values of the filament length, S, undulation wavelength, λ, and undulation amplitude. For the sawtooth and sinusoids these occur for undulation numbers Nλ = S/λ ≈ 3/2, 5/2, 7/2, …, whereas for the square wave strategy these occur at Nλ ≈ 1/2, 3/2, 2, 3, 4, …. We analyze swimming in terms of pitching as well as translation and bobbing, which are motion along and orthogonal to the net direction of translation, respectively. Resonances for the sawtooth and smooth waveforms occur when pitching is small and bobbing is near a local maximum. However, for square-wave actuation, most resonances occur when bobbing is small and pitching is near a local maximum.
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