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  • 1
    Electronic Resource
    Electronic Resource
    Hybridization between σ- and z-co-ordinates for improving the internal pressure gradient calculation in marine models with steep bottom slopes (1997)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 25 (1997), S. 1003-1023 
    Details
    ISSN: 0271-2091
    Keywords: 3D modelling systems ; general vertical co-ordinates ; pressure gradient ; hydrostatic consistency ; momentum advection ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: It is discussed in this paper how the pressure gradient error in general vertical co-ordinate models (in which the σ-transformation is a special case) can be reduced by means of hybrid models. For a better understanding, the derivation of such a general vertical co-ordinate model from the Cartesian co-ordinate model is given. Two types of hybridization between σ- and z-co-ordinate models, each using one parameter specifying the degree of hydridization, are presented: (i) the mixed layer transformation with a constant number of layers which are refined near the surface and (ii) the z/σ-transformation which introduces steps near the bottom. In order to achieve good results with the models using other than σ-co-ordinates, a profile-conserving momentum advection discretization is developed. The different co-ordinate transformations are tested with 2D barotropic and baroclinic flows over a topographic bump. Those models with nearly horizontal co-ordinate surfaces in the stratified area give the best correspondence with an isopycnal reference solution. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
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    Processes of Stratification and Destratification During An Extreme River Discharge Event in the German Bight ROFI (2021)
    Details
    Publication Date: 2021-07-04
    Description: Processes of stratification and destratification in the German Bight region of fresh water influence (ROFI) are investigated following an extreme river discharge event in June 2013. For this purpose, a high‐resolution baroclinic ocean model is set up and validated against field data. The model results are used to study the temporal and spatial variability of stratification and the duration of persistent stratification in 2013. The relevant processes affecting stratification are investigated by analyzing the potential energy anomaly budget, with a focus on mixing and tidal straining. It is shown that the stratification in the German Bight is highly affected by the spring‐neap tidal cycle, with generally less stratification at spring tides due to dominant tidal mixing. It is also shown that the location of the river plume can modify this pattern. During spring tides, if the river plume is confined to the eastern region, stratification decreases significantly, as expected, due to the dominance of mixing over tidal straining. On the other hand, if the river plume moves toward deeper regions at spring tides, strong tidal straining becomes present. In this condition, mixing is weak, and the dominant tidal straining results in persistent stratification.
    Description: Key Points: Processes impacting the German Bight stratification are investigated using a high‐resolution baroclinic model. The position of the river plume highly affects the contribution of tidal straining and mixing to changes in stratification. Strong tidal straining can result in persistent stratification even during spring tides.
    Description: Bundesministerium für Bildung und Forschung (BMBF) http://dx.doi.org/10.13039/501100002347
    Description: German Research Foundation http://dx.doi.org/10.13039/501100001659
    Description: German Environment Agency http://dx.doi.org/10.13039/501100010809
    Keywords: 551.46 ; stratification ; tidal‐straining ; mixing ; extreme river discharge ; numerical model ; German Bight ROFI
    Type: article
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