Meeting Abstract

P1-99   -   Wake characteristics of multi-appendage flapping and rowing at low Reynolds number Webb, GD*; Ford, MP; Santhanakrishnan, A; Oklahoma State University; Oklahoma State University; Oklahoma State University askrish@okstate.edu http://www.appliedfluidslab.org

Aquatic organisms primarily use two different locomotion strategies—rowing and flapping—across wide ranges of swimming speeds, body sizes and body morphologies. Metachronal rowing is a drag-based swimming strategy used by numerous species of arthropods, where a series of appendages are oscillated in sequence to generate propulsive force mostly parallel to appendage motion. In contrast, flapping of fins or tails provides lift-based propulsion, where propulsive force is mostly perpendicular to appendage motion. While flapping is mostly used by animals that swim at large scales (Reynolds numbers greater than 1,000), rowing is mostly used by smaller-scaled animals (Reynolds numbers less than 1000). For a single appendage, flapping is generally considered to be more efficient than rowing. However, it is unknown whether this holds true for multiple appendages working in coordination. Using a robotic swimming model, we characterize the hydrodynamic effects of varying phase lag and mean appendage orientation angle on the fluid wake. We find that increased phase delay leads to increased interactions between vortices and increased wake flow. Both rowing and flapping show an increase in horizontal momentum flux due to these interactions; however, the rate of increase of horizontal momentum flux differs. Comparisons between flow characteristics of the locomotion strategies will be discussed.