Size and Swimming Velocity in Nature
Subject Area
Biology
Description
Samantha Borruso ’23
Major: Biology
Faculty Mentor: Dr. Jack Costello, Biology
Swimmers and flyers both move through fluids – water and air. However, the fluids differ and a common metric used to quantitatively describe these differences is termed the Reynolds number (Re). Technically, Re quantifies the ratio of inertial to viscous forces that affect an organism moving through a fluid. Most large organisms operate in high Re flows where momentum is an important factor. These high Re swimmers are often viewed as energetically effective since they can readily transfer momentum from their moving body to fluid. In contrast, small organisms at low Re live in a viscous world characterized by “sticky” fluid interactions. It is believed this causes them to expend tremendous amounts of energy since they lack inertia and must continuously employ propulsors in order to move forward. This has led to the assumption of swimming ineffectiveness at lower Re. However, this study challenges this perceived notion with a multi-taxonomic database highlighting sizes and steady state swimming velocities of hundreds of organisms. A metric of size specific velocity with the units of body lengths per second was used to compare speeds of organisms across phyla, with organisms with higher specific velocities considered more efficient. The data collected thus far suggests that a higher Re is not more effective by this metric, and the perception that organisms of lower Re are energetically disadvantaged can no longer be automatically assumed.
Publisher
Providence College
Date
4-27-2023
Type
Presentation
Language
English
