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Modelling physical processes of haline stratification in ROFIs with application to the Rhine outflow region
Luyten, P.J. (1997). Modelling physical processes of haline stratification in ROFIs with application to the Rhine outflow region, in: Ruddick, K. Processes in regions of freshwater influence (PROFILE): selected papers from the 27th International Liège Colloquium on Ocean Hydrodynamics, held in Liège, Belgium, on May 8-12, 1995. Journal of Marine Systems, 12(Special Issue 1-4): pp. 277-298. dx.doi.org/10.1016/S0924-7963(96)00103-0
In: Ruddick, K. (1997). Processes in regions of freshwater influence (PROFILE): selected papers from the 27th International Liège Colloquium on Ocean Hydrodynamics, held in Liège, Belgium, on May 8-12, 1995. Journal of Marine Systems, 12(Special Issue 1-4). Elsevier: The Netherlands. 1-326 pp., more
In: Journal of Marine Systems. Elsevier: Tokyo; Oxford; New York; Amsterdam. ISSN 0924-7963, more
Peer reviewed article  

Available in Author 
    VLIZ: Open Repository 237450 [ OMA ]
Document type: Conference paper

Keywords
    Tides; Turbulence; Marine; Fresh water
Author keywords
    Numerical modeling; Estuarine processes

Author  Top 
  • Luyten, P.J., more

Abstract
    A physical and numerical study is made of the processes governing the stratification and circulation in ROFIs (Regions of Freshwater Influence) where there is an important impact of wind and tides. Observations in the Rhine ROFI showed that the salinity field consists of a mean and a tidally oscillating part. The physical processes are first analysed using the analytical solutions from a one-dimensional two-layer model. A justification is given for the neglection of non-linear advective terms in the equations of momentum and salinity. The dimensionless forms of the solutions can be expressed in terms of a series of dimensionless numbers. It is shown in particular that stratification and cross-shore circulation largely depend on the balance between rotation and turbulent diffusion, which depends in turn on parameters such as the Ekman number, the bottom friction coefficient, the eddy viscosity ratio and the depth of the layer interface. Surface winds either enhance or destroy stratification depending on the wind angle. The response to wind forcing is discussed using classical Ekman theory. To verify the analytical theory numerical tests are performed with a point model including an advanced turbulence closure scheme. Differences arise due to the non-linear interaction between turbulence on the one hand and current shear and stratification on the other hand. It is shown in particular that the amplitude of the tidal forcing and the off-shore horizontal salinity gradient strongly affect the semi-diurnal and semi-monthly variation of stratification. The effect of the wind is found to be in good agreement with the analysis of the two-layer model. Finally, the numerical model is compared with existing observational data in the Rhine ROFI for October 1990.

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