12-6 Sat Jan 2 Effects of hinge angle variation on metachronal paddling Kasoju, VT; Ford, MP*; Santhanakrishnan, A; Oklahoma State University; Oklahoma State University; Oklahoma State University askrish@okstate.edu http://www.appliedfluidslab.org
Crustaceans such as krill and many other ecologically important marine invertebrates stroke multiple appendages in an oscillatory pattern as a mode of locomotion, known as metachronal swimming. During a metachronal stroke, each swimming appendage (pleopod) is moved with a phase lag relative to its neighboring appendage. Crustacean pleopods are typically jointed, with the bottom portion (endopodite and exopodite) being able to fold up during recovery stroke (posterior-to-anterior motion) to reduce drag, while unfolding during power stroke (anterior-to-posterior motion) to increase thrust. Previous studies have reported on the variation in phase lag (φ) and joint angle (β) of each pleopod. Changes in φ and in the limits of β could help an animal achieve more thrust or lift generation necessary to achieve horizontal or vertical motion, or hovering. In this study, we investigate the effects of variation in φ and β on lift and drag using a two-dimensional computational model with 5 flat-plate paddles, each with a hinge halfway along its length. Modeling was performed in ANSYS Fluent 2019 R3, and the motion of both the top and bottom portions of the paddles was prescribed. Both the stroke amplitude of the upper (root) portion of the appendage (75 degrees) and the stroke frequency (2.5 Hz) were kept constant. We examined the force generation, inter-appendage pressure distributions, and fluid dynamic characteristics of the wake for varying minimum β in the range of 120-180 degrees and φ in the range of 0%-30% of cycle time. While keeping φ constant, varying β from 120-135 degrees showed little to no variation in the vortex wake behind the tail-most paddle after the start of recovery stroke.