  Scaling laws for the thrust production and power consumption of a purely
pitching hydrofoil in ground effect are presented. For the first time, ground
effect scaling laws based on physical insights capture the propulsive
performance over a wide range of biologically-relevant Strouhal numbers,
dimensionless amplitudes, and dimensionless ground distances. This is achieved
by advancing previous scaling laws (Moored & Quinn 2018) with physics-driven
modifications to the added mass and circulatory forces to account for ground
distance variations. The key physics introduced are the increase in the added
mass of a foil near the ground and the reduction in the influence of a wake
vortex system due to the influence of its image system. The scaling laws are
found to be in good agreement with new inviscid simulations and viscous
experiments, and can be used to accelerate the design of bio-inspired
hydrofoils that oscillate near a ground plane or two out-of-phase foils in a
side-by-side arrangement.
