River computations

artificial backwater from the momentum advection scheme

Journal article (2018)

Authors

F.W. Platzek Environmental Fluid Mechanics - CEG , Deltares
G.S. Stelling Environmental Fluid Mechanics - CEG
Jacek A. Jankowski Bundesanstalt für Wasserbau
R. Patzwahl Bundesanstalt für Wasserbau
J.D. Pietrzak Environmental Fluid Mechanics - CEG
Research Group
Environmental Fluid Mechanics (CEG) (TU Delft)
Topography River Groyne Artificial backwater Energy head Momentum advection
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Published Date

28-02-2018

Language

English

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Faculty

Civil Engineering & Geosciences

Department

Hydraulic Engineering

Research Group

Environmental Fluid Mechanics

Abstract

The established method for determining dike heights and dimensioning river training structures is to assess the resulting backwater by numerical modelling. The common consensus is that bottom friction determines the backwater and that momentum advection only has a local effect. We demonstrate that the numerical/artificial backwater contribution from the momentum advection approximation can be of the same order of magnitude as the bottom friction contribution, depending on the advection scheme. This is realized using a one-dimensional analysis and verified using a set of one- and two-dimensional test problems including a wavy bed case, flow over emerged and submerged groynes and finally an actual river. We compare first- and second-order accurate advection schemes and compute their artificial contribution to the backwater, for a range of practically-feasible grid resolutions. The tests demonstrate that the conservation/constancy properties of the scheme determine the size of this contribution, rather than the order of the scheme.