ASSESSING THE IMPACT OF PHENOMENOLOGICAL VISCOSITY MODEL UNCERTAINTIES ON THE NUMERICAL SIMULATION OF NON DILUTE TURBIDITY CURRENTS

Henrique José Ferreira da Costa¹; Gabriel Mario Guerra¹; Fernando Alves Rochinha¹; Alvaro L.G.A. Coutinho²

¹ Universidade Federal do Rio de Janeiro - COPPE/PEM/LMS; ² Universidade Federal do Rio de Janeiro - COPPE/PEC -NACAD

doi:10.20906/CPS/COB-2015-1008

Resumo

Turbidity currents are particular particle-laden flows driven by the presence of sediments which generate local density gradients responsible for the motion. Besides being transported by the fluid, the sediments, due to gravity, are able to move downwards and settle. The study of turbidity currents aims to improve the understanding about the formation of sedimentary basins that might host oil reservoirs. The actual conditions in which those complex turbulent flows occurs are very difficult to be reproduced in laboratory environments, what motivates the use of numerical simulation to achieve such goals. Between several phenomena affected and generated by the presence of sediments, the fluid rheology can present significant alteration, especially for non-dilute flows. This non standard rheological behavior must be taking into account in the numerical model, which, often, is carried out through phenomenological constitutive-like equations for the effective viscosity of the mixture (fluid + sediments). Therefore, one must consider the reliability of such models plugged into the balance equations, with special concern about uncertainties in those models. In this sense, Uncertainty Quantification (UQ) can provide a rational framework to assist in this task. Here, an initial study about the impact of the so called error model, in which uncertainties are supposed to be generated by the form of the phenomenological equations is presented. Literature shows different viscosity laws taking into consideration high sediments concentration, which are validated by several experiments. Here, a probabilistic perspective is employed in the context of the UQ analysis. More specifically, the viscosity law is built upon a nominal mathematical form with an embedded stochastic parameter that is responsible for addressing the uncertainty in the model. The UQ analysis uses a deterministic high optimized finite element parallel solver based on the Residual Based Variational Multiscale Method. A non intrusive stochastic collocation meth

Palavras-chave: non dilute turbidity currents; model uncertainties; uncertainty quantification