14 November 2019 - 12:00
Date: November 14
Time: 12:00 (Starting time, arrive earlier), 20:00 drinks at ‘t Postkantoor (Google map)
Location: Senaatszaal, Auditorium, Delft University of Technology (Google Map)
Symposium: Advances in Mathematical Modelling of Hydraulic and Morphodynamic Problems (13 november)
Contact candidate: firstname.lastname@example.org
Obtaining well-posedness in mathematical modelling of fluvial morphodynamics
Rivers carry sediment of different sizes. Modelling this characteristic is essential for properly predicting the effect of interventions (e.g., sediment nourishments). The current modelling approach sometimes catastrophically fails when accounting for mixed-size sediment, as the model is mathematically ill-posed. Currently, river managers do not have a reliable tool for predicting river morphodynamic changes accounting for mixed-size sediment. We conducted laboratory experiments aimed at gaining insight into the origin of the problem and in search of a possible solution. We used two sediment size fractions: fine (blue) and coarse (red). Degradational conditions were imposed, causing the entrainment of fine sediment. The current model cannot predict this situation. We have analyzed the conditions under which the current model becomes useless in practice: A large spurious oscillations develops that mixes the substrate sediment in an unrealistic manner. We have developed a tool to predict when will this happen in numerical simulations. We have conducted a set of laboratory experiments to gain insight into the physical reasons that cause failure of the current model. Using the results of the analysis and the laboratory data, we have developed a strategy that prevents the current model from failing. We have also developed a new model that describes the physical processes observed in the experiment that are not included in the current model.