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  - Rausch, Peter
A1  - Verpoort, Sven
A1  - Wittrock, Ulrich
T1  - Performance verification and environmental testing of a unimorph deformable mirror for space applications.
T2  - Proceedings of the 10th International Conference on Space Optics - ICSO, Tenerife, Spain
N2  - Concepts for future large space telescopes require an active optics system to mitigate aberrations caused by thermal deformation and gravitational release. Such a system would allow on-site correction of wave-front errors and ease the requirements for thermal and gravitational stability of the optical train. In the course of the ESA project "Development of Adaptive Deformable Mirrors for Space Instruments" we have developed a unimorph deformable mirror designed to correct for low-order aberrations and dedicated to be used in space environment. We briefly report on design and manufacturing of the deformable mirror and present results from performance verifications and environmental testing.
KW  - space optics
KW  - adaptive optics
KW  - deformable mirror
KW  - unimorph
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:836-opus-7716
UR  - http://www.icsoproceedings.org
PB  - FH Münster
ER  - 
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  -