Optimal Strouhal number for swimming animals
arXiv:1102.0223 · doi:10.1016/j.jfluidstructs.2012.02.008
Abstract
To evaluate the swimming performances of aquatic animals, an important dimensionless quantity is the Strouhal number, St = fA/U, with f the tail-beat frequency, A the peak-to-peak tail amplitude, and U the swimming velocity. Experiments with flapping foils have exhibited maximum propulsive efficiency in the interval 0.25 < St < 0.35 and it has been argued that animals likely evolved to swim in the same narrow interval. Using Lighthill's elongated-body theory to address undulatory propulsion, it is demonstrated here that the optimal Strouhal number increases from 0.15 to 0.8 for animals spanning from the largest cetaceans to the smallest tadpoles. To assess the validity of this model, the swimming kinematics of 53 different species of aquatic animals have been compiled from the literature and it shows that their Strouhal numbers are consistently near the predicted optimum.
21 pages, 6 figures
References in corpus (1)
Cited by in corpus (11)
- A fast Chebyshev method for simulating flexible-wing propulsion
- Surface microswimmers, harnessing the interface to self-propel
- Intermittent Unsteady Propulsion with a Combined Heaving and Pitching Foil
- How shape and flapping rate affect the distribution of fluid forces on flexible hydrofoils
- Numerical simulation of vortex-induced drag of elastic swimmer models
- Connections between propulsive efficiency and wake structure via modal decomposition
- A systematic investigation into the effect of roughness on self-propelled swimming plates
- Undulatory underwater swimming: Linking vortex dynamics, thrust, and wake structure with a biorobotic fish
- Flow associated with Lighthill's elongated-body theory
- Inviscid scaling laws of a self-propelled pitching airfoil
- Boundary layer flow dynamics of propulsive flapping foils with increasing Reynolds numbers