Author(s): U. Arnold; E. Pasche; G. Rouve
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Keywords: No Keywords
Abstract: The work described is an exper imental investigation into fluvial mixing processes. To achieve better agreement with results from natural rivers, special regard is given in this study to the problem of transverse mixing in channels with compound cross-section and highly vegetated flood-plain. Experiments were carried out in a straight laboratory flume with varying aspect ratios and flood-plain roughnesses. The velocities have been measured with a LDV-equipment providing not only mean but also tur bulent quantities. For visualization of the mixing process a conservative fluorescent dye solution was constantly injected from a submer ged vertical line source and activated by radiation of UV-A-light. Concentration profiles have been measured with a video system by means of digital-image-processing. The magnitude and distribution of the depth-averaged transverse diffusivity are derived from these exper imental data applying both the change of moment (SAYRE, l968) and the generalized change of moment method (Holley, l972). The resulting dimensionless diffusion coefficient shows a notable variation over the cross-section. A comparison with the tur bulence intensity profile leads to the conclusion that the transverse mixing process in the regior: near the fictive wall between main channel and flood-plain is dominated by transverse turbulent sher. Bed generated turbulence seems to be only of minor importance in these interacting parts of the cross-section.
Year: 1985