E3S Web Conf.
Volume 40, 2018River Flow 2018 - Ninth International Conference on Fluvial Hydraulics
|Number of page(s)||8|
|Section||Fluid mechanics and sediment processes|
|Published online||05 September 2018|
Velocity field and drag force measurements of a cube and a hemisphere mounted on an artificial bed surface roughness
Leichtweiß-Institute for Hydraulic Engineering and Water Resources, TU Braunschweig, Braunschweig, Germany
* Corresponding author: email@example.com
Quantification of the resistance in complex roughness situations, when both bed surface and form roughnesses contribute to the total resistance, as well as partitioning of the two contributions is still unsolved. Studies about form resistance of single elements focused on obstacles mounted on smooth bed surfaces, and only few considered a rough bed surface. In order to define an approach for shear stress partitioning in open channel flows, the effect of flow conditions, the geometrical characteristics of the obstacle, and the effect of the bed surface need to be studied. This paper contributes to the topic presenting results of experiments investigating the flow field around a cube and a hemisphere mounted on a bed surface with wake interference roughness. The velocity field and the drag force exerted on the obstacles were measured with a 3D Laser Doppler Anemometer and a drag force sensor, respectively. The double averaging methodology (DAM) was applied to define the characteristic region influenced by the cube and the hemisphere, and to analyse the streamwise velocities. DAM was developed for canopy flow, thus, the methodology needed to be adapted for isolated obstacle situations. A dependency of the drag coefficient on the relative submergence is observed and analysed.
© The Authors, published by EDP Sciences, 2018
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (http://creativecommons.org/licenses/by/4.0/).
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