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Form induced stresses over rough gravel-beds

Aberle J., Koll K., Dittrich A.

Acta Geophysica

2008

Vol. 56, no. 3

584-600

This paper presents an analysis of spatial flow heterogeneity over rough gravel beds for shallow flows in terms of form induced stresses. Data from experiments specifically designed with the intention to analyze the flow data with the double-averaging methodology are used to investigate the nature of form induced stresses. It is shown that spatial flow heterogeneity is small at greater distances to the roughness tops (z 100), increases slightly towards z 100, and increases significantly below z 100. Form induced stresses determined over the same bed and with the same slope are found to be independent of discharge. The influence of the number of measuring verticals on the magnitude of form induced stresses is discussed. The distributions of form induced stresses - are used to define the geodetic level of the roughness crest for rough, irregular beds from hydraulic data.

Hydrodynamics of aquatic ecosystems: spatial-averaging perspective

Nikora V.

Acta Geophysica

2007

Vol. 55, no. 1

3-10

Hydrodynamics of aquatic ecosystems is a relatively new, emerging multidis-ciplinary research area dealing with two key inter-connected issues: (i) physical in-teractions between flow and organisms (e.g., due to drag forces); and (ii) ecologi-cally relevant mass-transfer-uptake processes (e.g., due to molecular and turbulent diffusion). Owing to physical and biological complexity of boundary conditions in aquatic systems, the conventional hydraulic methodologies are often impracticable and new approaches are required. One of such approaches, the double-averaging methodology, is discussed with particular focus on flows over biologically-modified beds.