Chemical Plume Tracing

Abstract

Given a measurable concentration of a dissolved substance at a point within a fluid flow, where is the source? As physicists and engineers we often look at this problem from a more traditional perspective given a point source release of a substance, we seek to describe the temporal and spatial evolution of the effluent plume. Animals, seeking to evade predators or to locate mates or sources of food, contend with this problem routinely every day, and they have evolved a keen ability to locate these sources. Thus whereas our traditional approach when studying point source releases in the field of fluid mechanics is to seek to understand the fate of the source material and hence to study the forward problem, animals, and hence the biologists who study them, traditionally approach the study of the point-source-in-a-fluid as an inverse problem. This Special Issue on chemical plume tracing presents the work of an interdisciplinary research team, assembled by the Defense Advanced Research Projects Agency (DARPA) and the Office of Naval Research (ONR) to develop the ability to track chemical plumes to their sources. The fundamental approach to this research has been biomimetic. Both ONR and DARPA currently support research programs that seek either to integrate biological sensors or materials directly into new technology, or to capitalize on our knowledge about biological systems and processes to design new technological approaches to meet the demanding capability requirements of many armed services applications. This “biocentric” approach spans many disciplines and length scales. Some workers seek to enhance the performance of Navy surface and underwater platforms by a careful hydrodynamic analysis of swimming animals (Triantafyllou and Triantafyllou, 1995; Gordon et al., 2000; Bandyopadhyay, 2002). Others attempt to harness the power of single molecular motors to provide new energy sources (Montemagno and