  This study examines the impact of in-phase schooling on the hydrodynamic
efficiency during linear acceleration in a simplified model using two
undulating NACA0012 hydrofoils arranged in phalanx formation as a minimal
representation of a fish school. The research focuses on key parameters, namely
Strouhal (0.2-0.7) and Reynolds (1000-2000) numbers, and explores the effect of
varying fish-body wavelengths (0.5-2), reflecting natural changes during actual
fish linear acceleration. Contrary to expectations, in-phase schooling did not
enhance acceleration performance. Both propulsive efficiency and net thrust
were found to be lower compared to solitary swimming and anti-phase schooling
conditions. The study also identifies and categorizes five distinct flow
structure patterns within the parameters investigated, providing insight into
the fluid dynamics of schooling fish during acceleration.
