GLORIA

GEOMAR Library Ocean Research Information Access

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Articles  (596)
  • Wiley-Blackwell  (596)
  • 2015-2019  (596)
  • 2017  (596)
Document type
  • Articles  (596)
Source
Publisher
  • Wiley-Blackwell  (596)
Years
  • 2015-2019  (596)
Year
Journal
Topic
  • 1
    facet.materialart.
    Unknown
    Reply to Comment by Lu et al. on “An Efficient and Stable Hydrodynamic Model for Overland Flow and Flood Simulations” (2017)
    Wiley-Blackwell
    Details
    Publication Date: 2017-12-29
    Description: This document addresses the comments raised by [ Lu et al ., 2017]. [ Lu et al ., 2017] proposed an alternative numerical treatment for implementing the fully implicit friction discretization in [ Xia et al ., 2017]. The method by [ Lu et al ., 2017] is also effective, but not necessarily easier to implement or more efficient. The numerical wiggles observed by [ Lu et al ., 2017] do not affect the overall solution accuracy of the surface reconstruction method (SRM). SRM introduces an anti-diffusion effect, which may also lead to more accurate numerical predictions than hydrostatic reconstruction (HR) but may be the cause of the numerical wiggles. As suggested by [ Lu et al ., 2017], HR may perform equally well if fine enough grids are used, which has been investigated and recognized in the literature. However, the use of refined meshes in simulations will inevitably increase computational cost and the grid sizes as suggested are too small for real-world applications.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 2
    facet.materialart.
    Unknown
    Comment on “An Efficient and Stable Hydrodynamic Model With Novel Source Term Discretization Schemes for Overland Flow and Flood Simulations” by Xilin Xia et al. (2017)
    Wiley-Blackwell
    Details
    Publication Date: 2017-12-29
    Description: Xia et al . [2017] proposed a novel, fully-implicit method for the discretization of the bed friction terms for solving the shallow-water equations. The friction terms contain h –7∕3 (h denotes water depth) which may be extremely large, introducing machine error when h approaches zero. To address this problem, Xia et al . [2017] introduces auxiliary variables (their Eqs. (37)–(38)) so that h– 4∕3 rather than h –7∕3 is calculated and solves a transformed equation (their Eq. (39)). The introduced auxiliary variables require extra storage. We implemented an analysis on the magnitude of the friction terms to find that these terms on the whole do not exceed the machine floating-point number precision, and thus we proposed a simple-to-implement technique by splitting h –7∕3 into different parts of the friction terms to avoid introducing machine error. This technique does not need extra storage or solve a transformed equation and thus is more efficient for simulations. We also showed that the surface reconstruction method (SRM) proposed by Xia et al . [2017] may lead to predictions with spurious wiggles because the reconstructed Riemann states may misrepresent the water gravitational effect.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 3
    facet.materialart.
    Unknown
    Effects of Heterogeneity, Connectivity and Density Variations on Mixing and Chemical Reactions Under Temporally Fluctuating Flow Conditions and the Formation of Reaction Patterns (2017)
    Wiley-Blackwell
    Details
    Publication Date: 2017-12-29
    Description: Solute mixing, spreading and fast chemical reactions in aquifers are strongly influenced by spatial variability of the hydraulic properties, temporal flow fluctuations and fluid density differences. We study the coupling of heterogeneity, transient forcing and density-driven flow on mixing and chemical reactions between two fluids of different density under a stable stratification. We consider the reaction of the fast dissolution of calcite. We find that temporal fluctuations and heterogeneity cause strong local enhancement of the mixing and reaction rates and this impact increases with the degree of connectivity of hydraulic conductivity. The global mixing and reactivity, however, are on the order of or smaller than their homogeneous counterparts due to heterogeneity-induced fluid segregation. The local maxima of the mixing and reaction rates are found to be located around strongly stretched regions corresponding to high velocity zones where dispersive mass transfer mechanisms are increased by dispersion. We also find that density variations compress the interface, which in turn emphasizes local maxima in mixing and reaction rates. Numerical results provide evidence that the stretching of the interface induced by spatial heterogeneity and transient effects coupled with density variations leads to the formation of complex patterns of reactive hotspots, zones of enhanced reaction efficiency, and that its distribution is directly linked to the deformation properties and topology of the flow field. These results provide new insights into the role of spatial and temporal variability on the mixing and reaction efficiency as well as the formation of reactive geochemical patterns in actual environmental systems.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 4
    facet.materialart.
    Unknown
    Pore-Scale Determination of Gas Relative Permeability in Hydrate-Bearing Sediments Using X-Ray Computed Micro-Tomography and Lattice Boltzmann Method (2017)
    Wiley-Blackwell
    Details
    Publication Date: 2017-12-29
    Description: This work uses X-ray computed micro-tomography (μCT) to monitor xenon hydrate growth in a sandpack under the excess gas condition. The μCT images give pore-scale hydrate distribution and pore habit in space and time. We use the lattice Boltzmann method to calculate gas relative permeability ( k rg ) as a function of hydrate saturation ( S hyd ) in the pore structure of the experimental hydrate-bearing sand retrieved from μCT data. The results suggest the k rg - S hyd data fit well a new model k rg = (1- S hyd )·exp(-4.95· S hyd ) rather than the simple Corey model. In addition, we calculate k rg - S hyd curves using digital models of hydrate-bearing sand based on idealized grain-attaching, coarse pore-filling, and dispersed pore-filling hydrate habits. Our pore-scale measurements and modeling show that the k rg - S hyd curves are similar regardless of whether hydrate crystals develop grain-attaching or coarse pore-filling habits. The dispersed pore filling habit exhibits much lower gas relative permeability than the other two, but it is not observed in the experiment and not compatible with Ostwald ripening mechanisms. We find that a single grain-shape factor can be used in the Carman-Kozeny equation to calculate k rg - S hyd data with known porosity and average grain diameter, suggesting it is a useful model for hydrate-bearing sand.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 5
    facet.materialart.
    Unknown
    Hot Spots and Hot Moments of Nitrogen in a Riparian Corridor (2017)
    Wiley-Blackwell
    Details
    Publication Date: 2017-12-29
    Description: We use 3-D high-resolution reactive transport modeling to investigate whether the spatial distribution of organic carbon-rich and chemically-reduced sediments located in the riparian zone and temporal variability in groundwater flow direction impact the formation and distribution of nitrogen hot spots (regions that exhibit higher reaction rates when compared to other locations nearby) and hot moments (times that exhibit high reaction rates as compared to longer intervening time periods) within the Rifle floodplain in Colorado. Groundwater flows primarily towards the Colorado River from the floodplain, but changes direction at times of high river stage. The result is that oxic river water infiltrates the Rifle floodplain during these relatively short-term events. Simulation results indicate that episodic rainfall in the summer season leads to the formation of nitrogen hot moments associated with Colorado River rise and resulting river infiltration into the floodplain. The results further demonstrate that the naturally reduced zones (NRZs) present in sediments of the Rifle floodplain have a higher potential for nitrate removal, approximately 70% greater than non-NRZs for typical hydrological conditions. During river water infiltration, nitrate reduction capacity remains the same within the NRZs, however these conditions impact non-NRZs to a greater extent (approximately 95% less nitrate removal). Model simulations indicate chemolithoautotrophs are primarily responsible for the removal of nitrate in the Rifle floodplain. These nitrogen hot spots and hot moments are sustained by microbial respiration and the chemolithoautotrophic oxidation of reduced minerals in the riparian zone.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 6
    facet.materialart.
    Unknown
    Combined Flow Abstraction and Climate Change Impacts on an Aggrading Alpine River (2017)
    Wiley-Blackwell
    Details
    Publication Date: 2017-12-29
    Description: Recent climatic warming and associated glacial retreat may have a large impact on sediment release and transfer in Alpine river basins. Concurrently, the sediment transport capacity of many European Alpine streams is affected by hydropower exploitation, notably where flow is abstracted but the sediment supply downstream is maintained. Here, we investigate the combined effects of climate change and flow abstraction on morphodynamics and sediment transfer in the Borgne River, Switzerland. From photogrammetrically derived historical Digital Elevation Models (DEMs) we find considerable net aggradation of the braided river bed (up to 5 meters) since the onset of flow abstraction in 1963. Reaches responded through bed level steepening which was strongest in the upper most reach. Widespread aggradation however did not commence until the onset of glacier retreat in the late 1980s and the dry and warm years of the early 1990s. Upstream flow intake data shows that this aggradation coincided with an increase in sediment supply, although aggradation accounts for no more than 25% of supplied material. The remainder was transferred through the studied reaches. Estimations of bed load transport capacity indicate that flow abstraction reduces transport capacity by 1-2 orders of magnitude. Whilst residual transport rates vary with morphological evolution, they are in the same order of magnitude as the sediment supply rates, which is why significant transport remains. However, the reduction in transport capacity makes the system more sensitive to short-term (annual) changes in climate-driven hydrological variability and climate-induced changes in intake management and sediment delivery rates.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 7
    facet.materialart.
    Unknown
    Diurnal Course of Evaporation From the Dead Sea in Summer: A Distinct Double Peak Induced by Solar Radiation and Night Sea Breeze (2017)
    Wiley-Blackwell
    Details
    Publication Date: 2017-12-28
    Description: Partitioning between the relative effects of the radiative and aerodynamic components of the atmospheric forcing on evaporation is challenging since diurnal distributions of wind speed and solar radiation typically overlap. The Dead Sea is located about a hundred kilometers off the Eastern Mediterranean coast, where and the Mediterranean Sea breeze front reaches it after sunset. Therefore, in the Dead Sea the peaks of solar radiation and wind speed diurnal cycles in the Dead Sea are distinctly separated in time, offering a unique opportunity to distinguish between their relative impacts on evaporation. We present mid-summer eddy covariance and meteorological measurements of evaporation rate and surface energy fluxes over the Dead Sea. The evaporation rate is characterized by a clear diurnal cycle with a daytime peak, few hours after solar radiation peak, and a nighttime peak coincident with wind speed peak. Evaporation rate is minimum during sunrise and sunset. Measurements of evaporation rate from two other water bodies that are closer to the Mediterranean coast, Eshkol Reservoir and Lake Kinneret, present a single afternoon peak, synchronous with the sea breeze. The inland diurnal evaporation rate cycle varies with the distance from the Mediterranean coast, following the propagation of sea breeze front: near the coast, wind speed and radiation peaks are close and consequently a single daily evaporation peak appears in the afternoon; at the Dead Sea, about a hundred kilometers inland, the sea breeze front arrives at sunset, resulting in a diurnal evaporation cycle characterized by a distinct double peak.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 8
    facet.materialart.
    Unknown
    Issue Information (2017)
    Wiley-Blackwell
    Details
    Publication Date: 2017-12-23
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 9
    facet.materialart.
    Unknown
    Sediment Transport of Fine Sand to Fine Gravel on Transverse Bed Slopes in Rotating Annular Flume Experiments (2017)
    Wiley-Blackwell
    Details
    Publication Date: 2017-12-22
    Description: Large scale morphology, in particular meander bend depth, bar dimensions and bifurcation dynamics, are greatly affected by the deflection of sediment transport on transverse bed slopes due to gravity and by secondary flows. Overestimating the transverse bed slope effect in morphodynamic models leads to flattening of the morphology, while underestimating leads to unrealistically steep bars and banks and a higher braiding index downstream. However, existing transverse bed slope predictors are based on a small set of experiments with a minor range of flow conditions and sediment sizes, and in practice models are calibrated on measured morphology. The objective of this research is to experimentally quantify the transverse bed slope effect for a large range of near-bed flow conditions with varying secondary flow intensity, sediment sizes (0.17–4 mm ), sediment transport mode and bedstate to test existing predictors. We conducted over 200 experiments in a rotating annular flume with counter-rotating floor, which allows control of the secondary flow intensity separate from the streamwise flow velocity. Flow velocity vectors were determined with a calibrated analytical model accounting for rough bed conditions. We isolated separate effects of all important parameters on the transverse slope. Resulting equilibrium transverse slopes show a clear trend with varying sediment mobilities and secondary flow intensities that deviate from known predictors depending on Shields number, and strongly depend on bedstate and sediment transport mode. Fitted functions are provided for application in morphodynamic modelling.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 10
    facet.materialart.
    Unknown
    Variability of Bedload Transport During Six Summers of Continuous Measurements in Two Austrian Mountain Streams (Fischbach and Ruetz) (2017)
    Wiley-Blackwell
    Details
    Publication Date: 2017-12-22
    Description: Previous measurements of bedload transport in gravel-bed streams revealed a large temporal and spatial variability of bedload transport rates. Using an impact plate geophone system, continuous bedload transport measurements were made during six years in two mountain streams in Austria. The two streams have a snow- and glacier-melt dominated hydrologic regime resulting in frequent transport activity during the summer half year. Periods of days to weeks were identified which are associated with approximately constant Shields values that indicate quasi-stable bed conditions. Between these stable periods, the position of the bedload transport function varied while its steepness remained approximately constant. For integration time scales of several hours to one day, the fluctuations in bedload transport decreased and the correlation between bedload transport and water discharge increased. For integration times of about 70 to 100 days bedload transport is determined by discharge or shear stress to within a factor of about two, relative to the six year mean level. Bedload texture increased with increasing mean flow strength and mean transport intensity. Weak and predominantly clockwise daily hysteresis of bedload transport was found for the first half of the summer period.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...