Qian Liao

The Information Content of a Scalar Plume – A Plume Tracing Perspective

The ability of many animals and insects to track a plume to its source is a particularly impressive feat when the fluid dynamics is considered. Inspired by this observation this research seeks to identify the information in a passive scalar plume suitable for developing robust and efficient plume tracing algorithms. The subject of this study is a scalar plume emanating from a point source in a turbulent boundary layer which has been modeled in a laboratory facility built specifically for this purpose. A coupled PIV-LIF technique is used to measure the velocity and scalar field in a time resolved fashion. This data set is analyzed and the convergence rates of five single-point statistics, suitable as kernels of plume tracing algorithms, are investigated. The experimental data shows that the scalar fluctuations over long downstream distances from the source are characterized by filamentary structures that lead to relatively slow convergence rates for any statistic that is based on mean concentrations. The scalar intermittency, however, converges rapidly toward its true value, in fact converging to a testable hypothesis for source location direction faster than the time scale of the larger scale plume meander.

Simultaneous LIF and PIV Measurements of a Laboratory Modeled Coastal Plume

A new open-channel experimental facility has been built specifically for the study of coastal plumes. The research perspective is to investigate the physics from the point of view of the identification of contaminant source location. We present the preliminary results of a plume generated by a bottom-mounted source in the presence of lateral meanders. The measurements are made using a single camera simultaneous particle image velocimetry (PIV) – laser induced fluorescence (LIF) technique. The plume was released into a developing boundary layer, which it rapidly mixed across in the vertical; hence the majority of the plume growth was in the lateral direction. The lateral growth rate of the characteristic plume width was determined to be linearly proportional to the downstream distance, x. This somewhat surprising result is discussed.