Direct Numerical Simulations of turbidity currents with Evolutive Deposit Method, considering topography updates during the simulation

• Published in: Computers & geosciences 2019-12, Vol.133, p.104306, Article 104306
• Main Authors: Lucchese, Luísa Vieira, Monteiro, Leonardo Romero, Schettini, Edith Beatriz Camano, Silvestrini, Jorge Hugo
• Format: Article
• Language: English
• Subjects: DNS; Evolutive deposit method; Tridisperse; Turbidity current
• ISSN: 0098-3004; 1873-7803
• DOI: 10.1016/j.cageo.2019.104306

It is well-known that deposits of turbidity currents can significantly change bathymetry. The deposit of a current can alter sedimentation that happens afterwards, changing the deposit shape of a turbidity current. Direct Numerical Simulations of tridisperse turbidity currents are performed considering a rectangular channel and finite-release initial condition. The results are successfully compared to numerical and experimental results. We developed the Evolutive Deposit Method (EDM), that calculates the deposited volume and updates the topography based on the accumulated deposit for a given period of time. Entrainment is not considered. EDM has an original mathematical formulation. Topography update occurs at every τ and is based on two surfaces: Ψ and Γ. Ψ is a reference surface that can only assume integer mesh nodes, and defines the location of the solid represented by Immersed Boundary Method. Γ is a signed surface in which the deposit is integrated, and that is also fed by the rounding errors of Ψ. It is observed that the error caused by not considering the changes on topography due to deposit increases with time. For the case with initial flat terrain, the turbidity current front is the same whether considering the update or not. We also performed two simulations of turbidity currents propagating over the deposits produced by a previous current. In one case, the bathymetry was updated during both the first and the second events, and, in another, only changes on bathymetry between the simulations were considered. Results show that the order of magnitude of the relative deposit error of not considering bathymetry update remains the same order for both the first and the second consecutive events. •A method EDM to change bathymetry due to turbidity current deposit was developed.•The deposit was validated with experimental results using EDM.•Comparisons between constant and updated bottom were performed.•Overall deposit errors are the same order for two consecutive events.