University of Natural Resources and Life Sciences, Vienna (BOKU) - Research portal
Gewählte Master / Diploma Thesis:
Philipp Gmeiner
(2010):
Direkte Sohlschubspannungsmessung in einem Kiesbettfluss.
Master / Diploma Thesis - Institut für Wasserwirtschaft, Hydrologie und konstruktiver Wasserbau (IWHW),
BOKU-Universität für Bodenkultur,
pp 164.
UB BOKU
obvsg
- Abstract:
- The temporal and spatial bed shear stress distribution represents an important link between turbulent flow conditions and sediment transport. Hence bed shear stress is a fundamental parameter to describe and predict morphodynamic processes. Thus it is necessary to measure the fluctuating bed shear stress, in order to obtain not only mean values, but also variability, minima and maxima of this parameter, to draw conclusions in terms of critical shear stress, respectively the initiation of motion. The objective of this thesis was the design, construction and a functional test of a device for direct measurements of the fluctuating bed shear stress in a gravel bed river. The principle of the adopted measurement technique is to allow a shear plate covered with roughness elements to move freely in horizontal directions under the forces exerted by the flowing water and to measure the forces acting on the plate. In this case the forces occurring are measured with two strain stress transducers which are oriented perpendicular to each other. In a laboratory flume test the functionality of the approaching flow device was confirmed and a validation of the directly measured bed shear stress was in good agreement with calculated and modelled independent data sets. Moreover a resonance frequency analysis as well as statistical analyses of the directly measured bed shear stress were performed, indicating that the bed shear stress can be described by a Gaussian function. Using a three point suspension during the first tests in the Danube River an excellent stability behaviour was achieved when lowering the device to the river bed. Therefore after design, construction and the first successful measurements in the laboratory, for the first time a device is available for the direct measurement of the bed shear stress in gravel bed rivers. Future work aims at testing the functional capability of the device for field measurements.
- Beurteilende(r): Habersack Helmut
- 1.Mitwirkender: Liedermann Marcel Georg