Hydrodynamic Efficiency of Robotically Controlled Aurelia aurita in a Vertical Water Treadmill

Energy consumption is a limiting factor for mission duration of existing ocean monitoring techniques. Jellyfish have the lowest cost of transport of all metazoans and live in a wide range of ocean temperature, salinity, pH, and depth, making them ideal candidates for ocean monitoring robots. Aurelia aurita jellyfish stimulated with microelectronic swim controllers could serve as ocean sensors combining the benefits of low energy use, regenerative capabilities of live tissue, and inexpensive electronics. Previous work has demonstrated enhanced jellyfish vertical swimming speeds of 2.8 times baseline speeds without swim controllers. Indirect measurements suggest that this enhanced swimming can be achieved without proportional increases in energy consumption. Here, we examine this question using direct measurements of the hydrodynamic efficiency of robotically controlled Aurelia aurita associated with enhanced swimming speeds. Using PIV, we measure the kinetic energy of water set in motion by the animals to determine hydrodynamic efficiency. We utilize a 3,600-gallon tank to create a vertical water treadmill. This work demonstrates a new technique to characterize swimming performance in untethered aquatic species and connect wake measurements to swimming performance.