Ill-posedness in modelling 2D river morphodynamics
Víctor Chavarrías (TU Delft - Rivers, Ports, Waterways and Dredging Engineering)
W Ottevanger (Deltares)
RJ Labeur (TU Delft - Environmental Fluid Mechanics)
A Blom (TU Delft - Rivers, Ports, Waterways and Dredging Engineering)
More Info
expand_more
Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.
Abstract
The set of
equations used in modelling river morphodynamics
needs to be (at least) wellposed to be
representative of the real natural phenomenon.
As we deal with a time dependent process
the solution needs to be wave-like to be
well-posed. In other words, the solution must have a domain of dependence and of influence. Otherwise, the future river state influences
the present solution, which is
physically unrealistic. Based on an
analysis of the system of equations to
model one-dimensional river morphodynamics
with unisize sediment and a Chezy-based
friction term, Cordier (2011) concluded
that the system is always well-posed. Stecca
(2014) extended the analysis to a mixture
of sediment with 2 size fractions and concluded that under degradational conditions the
system may become ill-posed. This result
supported the first analysis that found
ill-posedness in mixedsize sediment
morphodynamics conducted by RIbberink (1987)
assuming a simpler model. Here we extend
these analyses by adding the effects of
flow curvature which creates an intrinsically
3D flow referred to as secondary or spiral
flow (Van Bendegom, 1947). In this study
the flow is assumed bi-dimensional which implies that the secondary flow needs to be parameterized.