Collaborative Research. Biologically-Generated Flow by Plankton: Numerical Simulations and Experiments

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PROPOSAL NO.: CTS-0625976 / 0625898PRINCIPAL INVESTIGATOR: F. SOTIROPOULOS / J. YENINSTITUTION: U OF MINNESOTA / GEORGIA TECH.BIOLOGICALLY-GENERATED FLOW BY PLANKTON: NUMERICAL SIMULATIONS AND EXPERIMENTS This grant supports an interdisciplinary, collaborative research effort aimed at integrating recent advancements in experimental biological oceanography and computational fluid dynamics (CFD) modeling to develop and validate biologically realistic CFD models of freely swimming planktonic micro-organisms. Three different organisms will be studied because they are known to rely on different modes of aquatic propulsion: flapping for the snail and paddling for the krill (continuous paddling) and the copepod (bursts of thrust during escape). Also their respective flow regimes collectively span the range from viscosity-dominated to transitional, inertial-dominated flows. High resolution imaging using Schlieren optics and light microscopy will provide body and appendage geometry and kinematics reconstruction for each organism. This information will be used as input to generate anatomically realistic computational models, which will include the organism body and all swimming appendages. A multi-scale approach will be developed to account for the presence of microscopic hairs in organism appendages. High resolution, hair-resolving CFD simulations will be carried for individual hairy appendages to quantify their leakiness as a function of the local Reynolds number. This information will be used to model at the macroscopic (full organism) scale each hairy appendage as flexible, continuous but leaky surface whose average leakiness varies in the manner determined from the hair-resolving simulations. Flow visualization by 2-dimensional infra-red particle image velocimetry will be carried out to obtain highly resolved planar velocity fields around both tethered and freely swimming plankton. Large volume observations of isolated individuals and groups of individuals will provide the 3D trajectories that will yield the speed and acceleration exhibited by freely swimming plankton. These measurements will be used to fine-tune and validate the computational model. The proposed CFD model of plankton swimming will provide biological oceanographers with a novel and powerful research tool that can shed new light into the response of plankton to small-scale biological-physical-chemical signals in the sea. The proposed model will also yield answers to many important biological questions pertaining to the hydrodynamics of plankton swimming and the mechanisms such microscopic organisms have evolved to leverage viscous forces to produce thrust and achieve often striking levels of propulsive performance. Both graduate and undergraduate students will be involved in this project, whose the unique nature will provide the students with a rich, interdisciplinary research experience. Students will develop unique skills to become leaders in today's evolving research landscape that emphasizes and relies on the integration of bio-sciences with engineering. Interdisciplinary training will be further enhanced by on-going educational efforts, in particular the Georgia Tech NSF IGERT and REU programs in the area of aquatic chemical and hydromechanical signaling.