A simplified approach to address turbulence modula

Authors: Mariano I Cantero S Balachandar Alessandro Cantelli Gary Parker

Publish Date: 2013/08/10

Volume: 14, Issue: 2, Pages: 371-385

PDF Link

Abstract

Turbidity currents traversing canyonfan systems flow over bed slopes that decrease in the downstream direction This slope decrease eventually causes turbidity currents to decelerate and enter a netdepositional mode When the slope decrease is relatively rapid in the downstream direction the turbidity current undergoes a concomitantly rapid and substantial transition Similar conditions are found when turbidity currents debouch to fan systems with loss of lateral confinement In this work a simplified approach to perform direct numerical simulation of continuous turbidity currents undergoing slope breaks and loss of lateral confinement is presented and applied to study turbulence modulation in the flow The presence of settling sediment particles breaks the top–bottom symmetry of the flow with a tendency to selfstratify This selfstratification damps turbulence particularly near the bottom wall affecting substantially the flow’s ability to transport sediment in suspension This work reports results on two different situations turbidity currents driven by fine and coarser sediment flowing through a decreasing slope In the case of fine sediment after the reduction in the slope of the channel the flow remains turbulent with only a modest influence on turbulence statistics In the case of coarse sediments after the change in slope turbulence is totally suppressedMariano I Cantero gratefully acknowledges the support from CONICET CNEA and ANPCyT through PICT20102459 We gratefully acknowledge the support from Shell International Exploration and Production and from the National Center for Supercomputing Applications NCSA at the University of Illinois at UrbanaChampaign UIUC The participation of Gary Parker in this research was made possible by the National Center for Earth Surface Dynamics NCED a Science and Technology Center funded by the US National Science Foundation S Balachandar acknowledges support from National Science Foundation through the Grants OCE1131016 and OISE0968313

Keywords: