Shallow Dead Zone Dynamics (DFG)
Shallow flows are not simple; they contain important morphological heterogeneities that lead to complex flow structures. In case of considerable lateral changes of the flow cross-section, large and slow recirculating volumes of fluid can be formed: the shallow dead zones. These zones have major effects on the mass transport of dissolved substances and on sediment transport. In addition, their flow structure has proven to be an important factor for stimulating the growth of the aquatic species; hence they are artificially created for river restoration purposes. Currently, their flow structure and the effects on mass transport cannot be totally predicted, due to the lack of knowledge of their flow dynamics and their dependency on the local geometry and incoming flow characteristics. This work aims to improve the understanding of the three-dimensional flow dynamics of shallow dead zones, including the spatio-temporal characterization of turbulence, coherent structures and water surface oscillations. A series of schematic laboratory experiments focusing on simple dead zones (harbor-like) and dead zone sequences (e.g. river groynes) for both the emerged and the submerged conditions. The experiments are currently conducted using an advanced Stereo Particle Tracking/Image Velocimetry technique, together with synchronous water level sensors. It is expected that this work will create one of the first experimental three-dimensional descriptions of the flow structure in shallow dead zones, and form the basis for improved hydrodynamics models dealing of their flow dynamics.