THRUST CHARACTERIZATION FOR BIO-INSPIRED PULSATILE VORTEX RING THRUSTERS WITH VARIABLE EXIT NOZZLE DIAMETER

摘要

The thrust response of a bio-inspired pulsatile vortex ring thruster is explored for variable diameter exit nozzle profiles. Our pulsatile vortex ring thruster is composed of a plunger in a submerged cavity that oscillates to intake and expel fluid through an exit nozzle creating vortex rings which generate thrust. The diameter of the exit nozzle is expanded upon fluid intake to increase volume flow. Upon fluid expulsion the nozzle diameter is reduced to increase flow velocity. This allows for an increase in total thrust. The effect is a thrusting force from a positive net flux in momentum with a zero net flux in mass. This is loosely inspired by jellyfish which utilize the same orifice for both mass intake and expulsion. The thrust is directly measured for multiple diameter profiles. A selected diameter profile is either a constant exit nozzle diameter or a sinusoidal oscillation of exit nozzle diameter that corresponds to the plunger motion. The increase in thrust is analyzed with respect to variable diameter effects and compared to thrust results of constant exit diameter nozzles.