Accelerated Motions of a Fish-Like Foil from Impulsive Starts to Terminal States

Abstract

It is presented through numerical analysis that accelerated motions of a two-dimensional fish-like foil by fluid forces can be modeled from impulsive starts to terminal states. Time histories of drag coefficient and foil speed depend on a frequency and motion of a foil and amplitude of its caudal fin. Three models that take thrust, inertial drag and viscous drag into account for the time histories of foil speed and drag coefficient are suggested. It is indicated that the model using viscous drag is in good agreement with numerical solutions in various conditions for small Reynolds numbers. Thrust, drag and terminal velocity can be summarized by functions that are almost power laws of the foil frequency even for various wavy lateral oscillations of the midline of a foil.

Keywords

• fish
• acceleration
• fluid-structure interaction
• cip method