Aquatic Sciences Meeting, Albuquerque 2001

SS07 Biomechanics: Turbulent Mass Transfer (Environmental Connections)

Date: Monday, February 12, 2001, Time: 2:15:00 PM

Location: San Miguel

McNair, J, N, Academy of Natural Sciences of Philadelphia, Philadelphia, PA, USA, mcnair@acnatsci.org

THE LOCAL EXCHANGE MODEL: A SIMPLE STOCHASTIC DIFFUSION MODEL OF TURBULENT PARTICLE TRANSPORT

The Local Exchange Model (LEM) provides a stochastic diffusion approximation to the random-like motion of particles suspended in a turbulent fluid. Ecological examples of such particles include fine particulate organic matter (FPOM), benthic invertebrate larvae, and fish larvae. In cases where flow is steady, the LEM permits relatively simple calculation of a variety of important properties of particle trajectories. These properties include the moments and probability distribution of the time required to hit bottom for the first time from a given initial elevation (the hitting time) and the corresponding longitudinal distance traveled (the hitting distance). It is also relatively simple to calculate the moments and probability distribution of the time and distance required to settle on the bottom, allowing for the possibility that a particle may encounter the bottom several times before it settles. Though the LEM does not address the fine structure of turbulence, several of its key properties compare favorably with published data sets, including recent data on the transport of C14-labeled FPOM in natural streams.

This Session Listing

Aquatic Sciences Meeting, Albuquerque 2001

Quicklinks