Meeting Abstract

7.4  Thursday, Jan. 3  Comparison of the Hydrodynamic Wakes of Temperate and Tropical Euchaeta species CATTON, K.B.*; WEBSTER, D.R.; YEN, J.; Georgia Institute of Technology; Georgia Institute of Technology; Georgia Institute of Technology gtg723v@mail.gatech.edu

Different species of the copepod genus Euchaeta live in polar, temperate, and tropical ocean environments. Euchaeta elongata is a species found in temperate waters that has nearly twice the prosome length compared to the tropical species Euchaeta rimana (4.2 mm vs. 2.4 mm). The kinematic viscosity of the ocean water in the colder, temperate ocean (8 deg C, ν = 1.4 mm² s^-1) is greater than the kinematic viscosity of the water in tropical environments (24 deg C, ν = 0.9 mm² s^-1). Reynolds number, which is a function of organism size, water viscosity, and swimming velocity, is a dimensionless parameter used to describe the flow regime. We hypothesize that this genus of copepods operates at an optimum Reynolds number that is advantageous for minimizing wake structure during predatory cruising and maximizing propulsion during escapes. The average Reynolds number of both species was found to be on the order of 10 for cruising behavior and on the order of 100 for escapes. Particle Image Velocimetry (PIV) was used to quantify the wake structures of both copepod species during cruising and escaping behaviors. The escape wakes exhibit similar maximum velocities of approximately 20 mm s^-1 and maximum vorticities of 30 s^-1. Analysis of the wake structure will be used to address hypotheses regarding propulsion and conspicuousness.