Performance Enhancement With Flexible Nozzles Under Pulsatile Jet

Squids escape danger by inking and propel themselves via an enhanced jet by using intermittent pulses from its flexible funnel. Inspired by this, studies of discrete pulses through flexible nozzles were performed that showed a jet enhancement in thrust and inking caused by the conversion of elastic energy from the material to kinetic energy for the vortex ring. This performance increase depends on the dimensionless wave speed, c-hat, of the nozzle, which is defined by nozzle morphology and material properties. Here, the jet enhancement applications for boat locomotion and dye mixing are quantified. The boat locomotion tests, Reynolds number 10^4, showed the optimal c-hat =~ 4.0, and the velocity and cost of transport improved by 41.1% and 27.9% respectively at a pump frequency of 16hz. By pumping fluorescent dye into a large tank, at Reynolds number 10^5, the diffusion speed was measured from the cross-sectional area of dye over time, this showed the flexible nozzle increased the diffusion speed by an estimated 20% at a pump frequency of 12hz. A flexible nozzle could transform the aquatic transport industry by increasing the speed of a vessel, with a negligible change in power, providing potential for energy savings.