Fig. 3.
The object collecting performance of the five basic swimming modes. a The flow field at the beginning of the recovery phase. The feeding flow is integrated from this time instant until the end of the recovery phase to estimate the volume flow sucked in during the recovery. The stronger stopping vortex suggests a stronger feeding flow. b The definition of Qexchange. The equation estimates the volume of the feeding flow Volfeeding exchanged into the sub-umbrella region by applying the axisymmetric assumption and integrating the 2D velocity obtained from PIV along the reference line. c Qexchange of the five basic swimming modes. A higher value indicates that the robot can collect objects faster. The error bars represent the standard error of the mean. N is the number of trials