14106 research outputs found
Sort by
Berücksichtigung des Grundwassers in den Empfehlungen des Arbeitskreises „Baugruben“ (EAB)
No full text
Optimising the wave attenuation of bamboo fences using the numerical wave model SWASH
No full textMangroves protect tropical coastlines from flooding and erosion, reducing
flood risks along coastal communities worldwide. Nevertheless,
mangrove forests have experienced considerable losses due to activities
like urbanization and aquaculture, exposing coastal areas to wave
attack. To restore mangroves at eroding coastlines, structures formed
by bamboo poles and a brushwood filling are used to shelter the coast
from waves, and create a favourable habitat for mangrove colonization.
However, these structures often lose their brushwood filling during
storms, resulting in high maintenance costs. This study proposes
a new type of design to reduce maintenance expenses, consisting of
only vertical bamboo poles without a filling of brushwood. Structure
designs are evaluated for a case study in Demak, Indonesia, using the
numerical wave model SWASH to predict wave attenuation through
the structures. Field measurements and WaveWatch III data are analyzed
to obtain the design conditions for the structures in Demak.
SWASH is validated against laboratory experiments, and applied to
investigate the optimum number of rows and their optimum spacing
(in the direction of wave propagation). The model shows that for a
structure consisting of two rows of bamboo poles, the transmission
rate Et/Ei decreases from 75% to 55% when the row spacing in the
wave direction is increased from sx = 0.42 m to sx = 5.8 m. Larger
spacings do not result in less transmission, and at least three rows
are needed to have a transmission rate lower than 50 % - a common
wave reduction target used in restoration efforts with structures. This
study thus identifies potential strategies to maximize wave attenuation
by bamboo structures, which can be used to reduce wave attack along
muddy coasts without the need of a brushwood filling. Hereby, it provides
an economically and user friendly alternative with respect to the
previous brushwood structure designs, as it requires less material costs
and maintenance. In addition, this study presents a new method to
schematize these kind of structures in SWASH in an efficient way
CFD modeling of flow and local scour around submerged bridge decks
No full textThe level set method-based, multiphase hydro- and morphodynamic numerical model REEF3D is used for the simulation of the flow conditions and local scouring around submerged bridge decks. Presence of hydraulic jumps, bridge overtopping, pressurized jets and the resulting scouring make the selected test cases especially challenging from the numerical modelling point of view. The models are validated against experimental data. The influence of the submergence ratio on the prevailing flow and scouring is investigated. The level set method showed robustness and good accuracy for the treatment of the complex free surface as well as for the tracking of the mobile bed. The submergence ratio showed no clear correlation with the prevailing erosion/deposition patterns. As the simulations offered insights into the prevailing hydrodynamics and thus the relevance of numerical modelling was emphasized for such complex sediment transport problems
LAWA-Konzept Klimafolgenmonitoring für den Wassersektor. Schlussbericht der LAWA-KG Klimaindikatoren
No full text
