SEMINARIS DE LA FACULTAT DE GEOLOGIA I L'INSTITUT DE CIÈNCIES DE LA TERRA 'JAUME ALMERA'
hora: 15:00
lloc: Sala d'actes de l'Institut Jaume Almera

Ricardo SILVA JACINTO (Ifremer, Centre de Bretagne, Marine Geosciences Unity, França)

Numerical modelling of turbidity currents has been developed in the last two decades or more. The solved physics is mainly based on fluid mechanics by solving adapted versions of the Navier-Stokes equations. The solving frames used have been derived from density currents dynamics applied to sediment suspensions in a purely monophasic approach. Most of the sediment-suspensions intrinsic behaviour is often ignored.

The numerical tools under development at Ifremer extend the physical processes from density flows to high-concentrated sediment suspensions, which behaviour is biphasic. The degree of sophistication in these models is dependent on the available knowledge and the quantification of the model parameters. Hence, priority has been given to a lower level of flow resolution but to a higher integration of complex and sediment related processes such sediment rheology and the modulation of turbulence within the flows.

The amount of information available to apply turbidity currents modelling to deep-sea environments is often limited and the provided modelling results are not of a predictive quality. For instance, very little is known about the necessary initial conditions or the determining boundary conditions. The uncertainties of each case study, independently of the modelling frame, suggest a close control on the hypothesis underlying numerical modelling and on the quantification of the necessary parameters, in order to reduce the degrees of freedom. In such an approach, numerical modelling of turbidity currents is unable to be predictive but might be a quite extraordinary tool to simulate hypothesis and data based interpretations.

In order to present the numerical modelling under development at Ifremer we will focus on the cohesive suspensions rheology, the way rheology may modulate turbulence, and the way we may these small scale processes may be integrated in the numerical modelling of turbidity currents at the scale of the turbiditic systems in the deep-sea.