A novel method to compute the propulsive efficiency of undulating swimmers

In the context of undulating propulsion, decoupling thrust and drag has direct implications on computing propulsive efficiency. Computing efficiency remains convoluted as numerous methods to decoupling thrust and drag exist leading to various conclusions which are not always consistent. This report documents a novel procedure for computing efficiency based on control volume assessments of momentum and energy, which are computed using Computational Fluid Dynamics. By balancing the energy equation using a control volume approach, the energy being input into the flow by the swimmer can be measured and compared to the energy required to drive the swimming motion. A discrepancy between these values exists, a loss term, and is associated with profile drag. This control volume methodology has previously been applied to heaving and pitching foils and has shown non-zero efficiency for self-propelled states. Using the heaving and pitching foil results as a benchmark we aim to expand this work by considering undulating swimming motions numerically. Efficiency computations using this novel approach will then be compared to other methods. Our aim is to compare the methods in an attempt to understand the physics behind efficiency for undulating propulsion.