A planar concentration analysis (PCA) system is used for observing the transport and mixing of a tracer mass in a shallow turbulent free-surface wake flow of a large cylindrical obstacle. The nonintrusive, fieldwise PCA measuring technique is applied to evaluate depth-averaged mass concentrations by making use of light attenuation due to absorption and scattering processes related to a dissolved tracer mass. The scalar fields are decomposed into a low-frequency quasiperiodic part, the coherent flow, and a randomly fluctuating part. From accompanying near-surface velocity measurements, large-scale coherent structures are identified and related to the coherent mass fields. This allows one to assess the role of the large-scale vortices for advection and diffusion in shallow wake flows. The time–mean wake flow displays a self-similar spanwise distribution both for mass and velocity. The longitudinal development of shallow wakes initially shows the growth of unbounded wakes; in the wake far field an attenuated behavior applies.
Mass Transport in Shallow Turbulent Wake Flow by Planar Concentration Analysis Technique
TECHNICAL PAPERS
Mass Transport in Shallow Turbulent Wake Flow by Planar Concentration Analysis Technique
Abstract
Authors:
Received: April 12, 2007
Accepted: October 08, 2008
Published online: April 01, 2009
© 2009 ASCE
