Bio-Physical Coupling in Predator-Prey Interactions

Our goal is to understand the biological and physical processes involved in feeding in sufficient detail to quantitatively predict predator-prey contact rates. The objective of the present work is to explore the use of computational fluid dynamics to gain insights into quantitative features of typical feeding currents near copepods. In particular, we wish to study the shape and extent of the feeding current in three-dimensional space, and its relationship with how the feeding current is generated through the forcing of the water by the copepod. Effects of various forcing distributions and copepod shapes will be studied, with particular emphasis on the feeding current, energetic efficiency, as well as far-field detectability by other predators or prey. We examine some details of oceanic predator-prey interactions by combining knowledge about plankton and the oceanic environment within a framework of three-dimensional, numerical simulations. For realistic shapes, Reynolds numbers, and force distributions, the equations of motion with proper boundary conditions can only be solved by using numerical methods. In this work, a commercially available, state-of-the-art, finite-volume, code FLUENT (trademark) is used to calculate the feeding current. Because the shape of the copepod may be important in determining the configuration of the feeding currents, we employ curvilinear body-fitted coordinates to smoothly describe the body shape without the rough edges that would arise with Cartesian coordinates. In the simulations, the appendages that generate the feeding current are replaced by a distribution of forces acting on the water adjacent to and in front of the body. First, the accuracy of FLUENT is verified by simulating two viscous, zero Reynolds number flows for which analytical solutions are available. Then, simulations with realistic body shape and Reynolds numbers are carried out.