Speaker:
Date of Talk:
9/3/10
Affiliation:
Department of Civil, Environmental and Architectural Engineering University of Colorado- Boulder
Title:
Coral Fertilization as a Model System for Reactive Stirring and Mixing in Structured Flows
Abstract
In this talk I will discuss stirring and mixing of reactive scalars in the context of an ecological process. Corals and many other marine invertebrates utilize broadcast spawning as a reproductive strategy: to spawn, adult males and females extrude sperm and ova into the surrounding flow. The strategy then relies primarily on turbulent stirring (at large and moderate spatial scales) and molecular diffusion and sperm motility (at small scales) to bring the gametes together before possible fertilization can take place. Locally, the fertilization rate depends on the co-occurring concentrations of egg and sperm, and these concentration fields are shaped largely by the characteristics of the turbulent stirring. We seek to understand the role of structured stirring on the resulting success of the fertilization strategy.
Many previous studies have demonstrated the effect of stirring and mixing on reaction enhancement for two scalar species that initially share a material interface. The coral fertilization problem suggests a new class of problems where the two scalars are initially separated by a third scalar (the ambient flow) that potentially acts as a barrier to subsequent reactions. Using a combination of analytical, numerical, and experimental approaches, we demonstrate how structured stirring produces selective coalescence of the initially distant gametes, resulting in significant reaction (fertilization) enhancement. The results have implications for a broad range of problems involving mixing and reaction of initially distant scalars.
