A morphodynamic model for cohesive sediments transport

Abstract

The dynamics of cohesive sediments in natural water bodies is of great importance for coastal engineering. Quite often, it is necessary to assess sedimentological processes in regions where cohesive sediments are prevalent, such as in many harbors. Such assessments poses challenges, especially in quantitative evaluations, as the physics involved in the transport, sedimentation and erosion of cohesive sediments is rather complex. For that, by all means, it is important to have analysis tools capable of computing cohesive sediments dynamics. This paper presents the development of a vertically averaged eulerian transport model for suspended cohesive sediments. Such model is currently available on SisBaHiA  , which is a computational modeling system developed and maintained in COPPE/UFRJ. After describing the model implementation, we present a discussion on consistency and validation tests, for each implemented mechanism within the sedimentological process, with a focus in the erosion and sedimentation fluxes. In sequence, we compare model results with the theoretical results and, for some tests, with the results of the simulations performed with the Delft3D  and Telemac  modeling systems. These models are similar to the one presented in this paper, and are well accepted and widely used on professional projects and studies. The tests showed that the developed model results were consistent for all the evaluated mechanism, and hence it's positively verified.Keywords: Erosion and sedimentation; Environmental modeling; Sediments transport; Cohesive sediments. RESUMOA dinâmica de sedimentos coesivos em corpos d'água naturais é um tema de grande importância na prática da engenharia costeira, sendo recorrente a necessidade de serem feitos prognósticos sobre esses fenômenos. Devido ao fato da física que envolve o transporte desses sedimentos ser relativamente complexa, o desenvolvimento de estudos e avaliações em projetos de engenharia se mostram um desafio. Assim, é importante que existam ferramentas de análise capazes de descrever os processos sedimentológicos para sedimentos coesivos. Nesse sentido, este artigo apresenta o desenvolvimento de um modelo euleriano 2DH de transporte advectivo-difusivo de sedimentos coesivos em suspensão. Tal modelo está disponível no SisBaHiA  , um software computacional de modelagem, desenvolvido e mantido na COPPE/UFRJ. Após a implantação, procedeu-se a etapa de verificação dos mecanismos implementados. Os resultados do modelo foram confrontados com resultados teóricos e, para alguns testes, com os resultados das mesmas simulações feitas com o Delft3D  e o Telemac  , que são modelos similares ao desenvolvido neste trabalho. Os testes confirmaram que o modelo desenvolvido apresenta resultados consistentes para todos os mecanismos avaliados, sendo assim positivamente verificado. Palavras-chave:Erosão e sedimentação; Modelagem ambiental; Transporte de sedimentos; Sedimentos coesivos.

On characteristic hydraulic times through hydrodynamic modelling: discussion and application in Patos Lagoon (RS)

“…The mathematical models for Residence Time, Times of Renewal Rates and Water Age hereby presented were implemented and applied to three idealized channel cases and a natural water body using SisBaHiA ® , a professional well-tested computational system for hydrodynamic modelling registered by COPPE/UFRJ, http://www.sisbahia.coppe.ufrj.br/. This computational system has been successfully used in different projects and scientific research (González-Gorbeña et al, 2015;Peixoto et al, 2017;Rosman, 2018;Silva et al, 2019). Nevertheless, the following methodologies are not restricted to be used with SisBaHiA ® , and can be implemented in any other hydrodynamic numerical model.…”

Physical and Rheological Characteristics of Sediment for Nautical Depth Assessment in Bushehr Port and Its Access Channel

“…The solid volume fraction (also called volumetric concentration) is recorded as output in each step which is defined as the ratio of solid volume to total volume. One of the proposed relationships for determining the rate of decrease in the concentration of suspended sediments is the Krone relationship with the no-flow condition as follows [37]:…”