3D numerical modelling of turbidity currents |
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Authors: | Anastasios N Georgoulas Panagiotis B Angelidis Theologos G Panagiotidis Nikolaos E Kotsovinos |
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Institution: | 1.Laboratory of Hydraulics and Hydraulic Structures, Department of Civil Engineering,Democritus University of Thrace,Xanthi,Greece;2.Laboratory of Fluid Mechanics, Mechanical Department,Institute of Technology,Kavala,Greece |
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Abstract: | During floods, the density of river water usually increases due to a subsequent increase in the concentration of the suspended
sediment that the river carries, causing the river to plunge underneath the free surface of a receiving water basin and form
a turbidity current that continues to flow along the bottom. The study and understanding of such complex phenomena is of great
importance, as they constitute one of the major mechanisms for suspended sediment transport from rivers into oceans, lakes
or reservoirs. Unlike most of the previous numerical investigations on turbidity currents, in this paper, a 3D numerical model
that simulates the dynamics and flow structure of turbidity currents, through a multiphase flow approach is proposed, using
the commercial CFD code FLUENT. A series of numerical simulations that reproduce particular published laboratory flows are
presented. The detailed qualitative and quantitative comparison of numerical with laboratory results indicates that apart
from the global flow structure, the proposed numerical approach efficiently predicts various important aspects of turbidity
current flows, such as the effect of suspended sediment mixture composition in the temporal and spatial evolution of the simulated
currents, the interaction of turbidity currents with loose sediment bottom layers and the formation of internal hydraulic
jumps. Furthermore, various extreme cases among the numerical runs considered are further analyzed, in order to identify the
importance of various controlling flow parameters. |
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