TY  - CHAP
A1  - Boes, R.M.
A1  - Auel, C.
A1  - Hagemann, M.
A1  - Albayrak, I.
T1  - Sediment bypass tunnels to mitigate reservoir sedimentation and restore sediment continuity
T2  - Reservoir Sedimentation
N2  - Worldwide, a large number of reservoirs impounded by dams are rapidly filling up with sediments. As on a global level the loss of reservoir volume due to sedimentation increases faster than the creation of new storage volume, the sustainability of reservoirs may be questioned if no countermeasures are taken. This paper gives an overview of the amount and the processes of reservoir sedimentation and its impact on dams and reservoirs. Furthermore, sediment bypass tunnels as a countermeasure for small to medium sized reservoirs are discussed with their pros and cons. The issue of hydroabrasion is highlighted, and the main design features to be applied for sediment bypass tunnels are given.
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:836-opus-151569
SN  - 978-1-138-02675-9
SP  - 221
EP  - 228
PB  - Taylor and Francis Group
CY  - London, UK
ER  - 
TY  - CHAP
A1  - Auel, C.
A1  - Albayrak, I.
A1  - Boes, R.M.
T1  - Bedload particle velocity in supercritical open channel flows
T2  - Proc. 7th River Flow, Int. Conference on Fluvial Hydraulics (Schleiss et al. eds.)
N2  - Single glass sphere motion recordings were conducted in a transitional-rough bed open channel at steady and highly supercritical flow similar to hydraulic conditions in sediment bypass tunnels. A high speed camera with a maximum resolution of 2,560 × 2,160 pixels was used to record the movement of bedload particles with diameters of D = 5.3, 10.3 and 17.5 mm. An in-house developed Particle Tracking Velocimetry (PTV) program was used to determine the transport mode and velocities of each particle for a wide range of Froude numbers up to Fo = 6. The relative roughness defined as the ratio of the bed roughness height ks to the water depth h varied from ks/h = 0.02–0.03. Particles were observed to move in rolling and saltation modes depending on the Shields number. The particle velocity shows a linearly increasing relationship with both friction velocity and Froude number nearly independent on the particle diameter. A linear relationship was also found between rolling and saltating particle velocities indicating that particle velocity does not depend on the transport mode in the range of the investigated hydraulic conditions. Scaling of particle velocity with the wave celerity plotted as a function of the Froude number adequately merged external data sets with the present data. As a consequence, a linear fit for a large Froude number range was obtained.
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:836-opus-151579
SN  - 978-1-138-02674-2
SP  - 923
EP  - 931
PB  - Taylor and Francis
ER  - 
TY  - CHAP
A1  - Auel, C.
A1  - Albayrak, I.
A1  - Boes, R.M.
T1  - Laborversuche über die Partikelbewegung in schiessendem Abfluss (Laboratory experiments on particle motion in supercritical flows)
T2  - Proc. Int. Symposium “Wasser- und Flussbau im Alpenraum”, VAW Mitteilungen
Y1  - 2014
SP  - 147
EP  - 156
PB  - ETH Zurich
ER  - 
TY  - JOUR
A1  - Auel, C.
A1  - Albayrak, I.
A1  - Boes, R.M.
T1  - Turbulence characteristics in supercritical open channel flows: Effects of Froude number and aspect ratio
JF  - Journal of Hydraulic Engineering ASCE
N2  - An experimental investigation of supercritical uniform and gradually varied open channel flows is presented for a wide range of Froude numbers and flume width-to-flow depth aspect ratios. The instantaneous streamwise and vertical flow velocities were measured in a laboratory flume over the entire width using a two dimensional–laser Doppler anemometry (2D-LDA) system to determine turbulence intensities, and bed and Reynolds shear stresses. The mean velocity patterns show undulation across the flume, indicating the presence of counterrotating secondary current cells. These currents redistribute turbulence intensities and bed and Reynolds shear stresses across the flume. For aspect ratios ≤ 4−5, i.e., narrow open channel flow, the velocity-dip phenomenon is identified both in the streamwise velocity and the Reynolds shear stress distributions. For high aspect ratios, i.e., wide open channel flow, the strength of secondary currents diminish toward the flume center, resulting in a 2D flow farther away from the walls and no velocity-dip phenomenon. Froude number effects on the flow characteristics are less pronounced compared to the aspect ratio effects. At high Froude numbers, the results for narrow and wide open channel flows agree well with literature data. The log-law holds in the inner region across the entire flume width for all investigated Froude numbers and aspect ratios. The Reynolds shear stress distribution agrees well with the computed spanwise bed shear stress distribution. At the flume side walls, the bed shear stresses are 20–50 % higher than the mean values. These results are verified with an engineering example in which high sediment transport and corresponding deep abrasion patterns at the side walls were observed.
Y1  - 2014
U6  - http://dx.doi.org/10.1061/(ASCE)HY.1943-7900.0000841
ER  -