Fauci The investigator develops and implements computational methods for modeling the fluid dynamics problems of aquatic animal locomotion across a wide range of animal sizes. Of interest are both the dynamics of a single organism and the relationship of its morphology to its motility properties, and the collective hydrodynamic interactions of groups of swimmers with each other and their environment. Applications studied include bacterial chemotaxis in micropores, spermatozoa motility in the reproductive tract, and the coupling of active and passive tissue properties to the external swimming mechanics of a leech. Bacterial chemotaxis in micropores is of special interest, because the transport behavior of microorganisms through porous media is important in studying the contamination of groundwater supplies. Although bioremediation, the process by which microbes degrade contaminants, has field scale implications, the detailed study of pore-level behavior of the coupled fluid-contaminant-microbial system is essential. The project's computational model includes the detailed analysis of hydrodynamics, contaminant reaction, diffusion and convection, and the chemotactic responses of the swimming microbes. This allows the systematic study of the influence of different parameters, such as swimming speed, diffusion rates, microbial uptake rates, as well as stochastic parameters relating to the likelihood with which microbes change their swimming direction in response to the evolving contaminant field. This is difficult, if not impossible, to examine in a laboratory environment. The project studies the way organisms swim, using computational models. The organisms studied vary in size from bacteria to leeches. Of paramount importance in the study of bacterial transport in micropores is the growth of biofilms. Under certain physical and chemical conditions, microbes adhere to each other and the local pore structure. This biofilm growth affects and is affe cted by the local flow characteristics and contaminant transport. The computational model has the ability to model complex, dynamic fluid-structure interactions. Agglomeration is modeled by exerting appropriate binding stresses between discrete representations of organisms, that may hold them together, or, if fluid stresses are large, may yield and release the organisms. The model is a powerful tool for understanding biofilm processes at a micropore level. This has important consequences for environmental problems.
